Initial QSfera import

2026-06-07 10:20:04 +03:00
commit 2315f25754
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+The MIT License (MIT)
+
+Copyright (c) 2015 Microsoft Corporation
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
@@ -0,0 +1,12 @@
+# go-ansiterm
+
+This is a cross platform Ansi Terminal Emulation library.  It reads a stream of Ansi characters and produces the appropriate function calls.  The results of the function calls are platform dependent.
+
+For example the parser might receive "ESC, [, A" as a stream of three characters.  This is the code for Cursor Up (http://www.vt100.net/docs/vt510-rm/CUU).  The parser then calls the cursor up function (CUU()) on an event handler.  The event handler determines what platform specific work must be done to cause the cursor to move up one position.
+
+The parser (parser.go) is a partial implementation of this state machine (http://vt100.net/emu/vt500_parser.png).  There are also two event handler implementations, one for tests (test_event_handler.go) to validate that the expected events are being produced and called, the other is a Windows implementation (winterm/win_event_handler.go).
+
+See parser_test.go for examples exercising the state machine and generating appropriate function calls.
+
+-----
+This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
@@ -0,0 +1,41 @@
+<!-- BEGIN MICROSOFT SECURITY.MD V0.0.8 BLOCK -->
+
+## Security
+
+Microsoft takes the security of our software products and services seriously, which includes all source code repositories managed through our GitHub organizations, which include [Microsoft](https://github.com/microsoft), [Azure](https://github.com/Azure), [DotNet](https://github.com/dotnet), [AspNet](https://github.com/aspnet), [Xamarin](https://github.com/xamarin), and [our GitHub organizations](https://opensource.microsoft.com/).
+
+If you believe you have found a security vulnerability in any Microsoft-owned repository that meets [Microsoft's definition of a security vulnerability](https://aka.ms/opensource/security/definition), please report it to us as described below.
+
+## Reporting Security Issues
+
+**Please do not report security vulnerabilities through public GitHub issues.**
+
+Instead, please report them to the Microsoft Security Response Center (MSRC) at [https://msrc.microsoft.com/create-report](https://aka.ms/opensource/security/create-report).
+
+If you prefer to submit without logging in, send email to [secure@microsoft.com](mailto:secure@microsoft.com).  If possible, encrypt your message with our PGP key; please download it from the [Microsoft Security Response Center PGP Key page](https://aka.ms/opensource/security/pgpkey).
+
+You should receive a response within 24 hours. If for some reason you do not, please follow up via email to ensure we received your original message. Additional information can be found at [microsoft.com/msrc](https://aka.ms/opensource/security/msrc). 
+
+Please include the requested information listed below (as much as you can provide) to help us better understand the nature and scope of the possible issue:
+
+  * Type of issue (e.g. buffer overflow, SQL injection, cross-site scripting, etc.)
+  * Full paths of source file(s) related to the manifestation of the issue
+  * The location of the affected source code (tag/branch/commit or direct URL)
+  * Any special configuration required to reproduce the issue
+  * Step-by-step instructions to reproduce the issue
+  * Proof-of-concept or exploit code (if possible)
+  * Impact of the issue, including how an attacker might exploit the issue
+
+This information will help us triage your report more quickly.
+
+If you are reporting for a bug bounty, more complete reports can contribute to a higher bounty award. Please visit our [Microsoft Bug Bounty Program](https://aka.ms/opensource/security/bounty) page for more details about our active programs.
+
+## Preferred Languages
+
+We prefer all communications to be in English.
+
+## Policy
+
+Microsoft follows the principle of [Coordinated Vulnerability Disclosure](https://aka.ms/opensource/security/cvd).
+
+<!-- END MICROSOFT SECURITY.MD BLOCK -->
@@ -0,0 +1,188 @@
+package ansiterm
+
+const LogEnv = "DEBUG_TERMINAL"
+
+// ANSI constants
+// References:
+// -- http://www.ecma-international.org/publications/standards/Ecma-048.htm
+// -- http://man7.org/linux/man-pages/man4/console_codes.4.html
+// -- http://manpages.ubuntu.com/manpages/intrepid/man4/console_codes.4.html
+// -- http://en.wikipedia.org/wiki/ANSI_escape_code
+// -- http://vt100.net/emu/dec_ansi_parser
+// -- http://vt100.net/emu/vt500_parser.svg
+// -- http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
+// -- http://www.inwap.com/pdp10/ansicode.txt
+const (
+	// ECMA-48 Set Graphics Rendition
+	// Note:
+	// -- Constants leading with an underscore (e.g., _ANSI_xxx) are unsupported or reserved
+	// -- Fonts could possibly be supported via SetCurrentConsoleFontEx
+	// -- Windows does not expose the per-window cursor (i.e., caret) blink times
+	ANSI_SGR_RESET              = 0
+	ANSI_SGR_BOLD               = 1
+	ANSI_SGR_DIM                = 2
+	_ANSI_SGR_ITALIC            = 3
+	ANSI_SGR_UNDERLINE          = 4
+	_ANSI_SGR_BLINKSLOW         = 5
+	_ANSI_SGR_BLINKFAST         = 6
+	ANSI_SGR_REVERSE            = 7
+	_ANSI_SGR_INVISIBLE         = 8
+	_ANSI_SGR_LINETHROUGH       = 9
+	_ANSI_SGR_FONT_00           = 10
+	_ANSI_SGR_FONT_01           = 11
+	_ANSI_SGR_FONT_02           = 12
+	_ANSI_SGR_FONT_03           = 13
+	_ANSI_SGR_FONT_04           = 14
+	_ANSI_SGR_FONT_05           = 15
+	_ANSI_SGR_FONT_06           = 16
+	_ANSI_SGR_FONT_07           = 17
+	_ANSI_SGR_FONT_08           = 18
+	_ANSI_SGR_FONT_09           = 19
+	_ANSI_SGR_FONT_10           = 20
+	_ANSI_SGR_DOUBLEUNDERLINE   = 21
+	ANSI_SGR_BOLD_DIM_OFF       = 22
+	_ANSI_SGR_ITALIC_OFF        = 23
+	ANSI_SGR_UNDERLINE_OFF      = 24
+	_ANSI_SGR_BLINK_OFF         = 25
+	_ANSI_SGR_RESERVED_00       = 26
+	ANSI_SGR_REVERSE_OFF        = 27
+	_ANSI_SGR_INVISIBLE_OFF     = 28
+	_ANSI_SGR_LINETHROUGH_OFF   = 29
+	ANSI_SGR_FOREGROUND_BLACK   = 30
+	ANSI_SGR_FOREGROUND_RED     = 31
+	ANSI_SGR_FOREGROUND_GREEN   = 32
+	ANSI_SGR_FOREGROUND_YELLOW  = 33
+	ANSI_SGR_FOREGROUND_BLUE    = 34
+	ANSI_SGR_FOREGROUND_MAGENTA = 35
+	ANSI_SGR_FOREGROUND_CYAN    = 36
+	ANSI_SGR_FOREGROUND_WHITE   = 37
+	_ANSI_SGR_RESERVED_01       = 38
+	ANSI_SGR_FOREGROUND_DEFAULT = 39
+	ANSI_SGR_BACKGROUND_BLACK   = 40
+	ANSI_SGR_BACKGROUND_RED     = 41
+	ANSI_SGR_BACKGROUND_GREEN   = 42
+	ANSI_SGR_BACKGROUND_YELLOW  = 43
+	ANSI_SGR_BACKGROUND_BLUE    = 44
+	ANSI_SGR_BACKGROUND_MAGENTA = 45
+	ANSI_SGR_BACKGROUND_CYAN    = 46
+	ANSI_SGR_BACKGROUND_WHITE   = 47
+	_ANSI_SGR_RESERVED_02       = 48
+	ANSI_SGR_BACKGROUND_DEFAULT = 49
+	// 50 - 65: Unsupported
+
+	ANSI_MAX_CMD_LENGTH = 4096
+
+	MAX_INPUT_EVENTS = 128
+	DEFAULT_WIDTH    = 80
+	DEFAULT_HEIGHT   = 24
+
+	ANSI_BEL              = 0x07
+	ANSI_BACKSPACE        = 0x08
+	ANSI_TAB              = 0x09
+	ANSI_LINE_FEED        = 0x0A
+	ANSI_VERTICAL_TAB     = 0x0B
+	ANSI_FORM_FEED        = 0x0C
+	ANSI_CARRIAGE_RETURN  = 0x0D
+	ANSI_ESCAPE_PRIMARY   = 0x1B
+	ANSI_ESCAPE_SECONDARY = 0x5B
+	ANSI_OSC_STRING_ENTRY = 0x5D
+	ANSI_COMMAND_FIRST    = 0x40
+	ANSI_COMMAND_LAST     = 0x7E
+	DCS_ENTRY             = 0x90
+	CSI_ENTRY             = 0x9B
+	OSC_STRING            = 0x9D
+	ANSI_PARAMETER_SEP    = ";"
+	ANSI_CMD_G0           = '('
+	ANSI_CMD_G1           = ')'
+	ANSI_CMD_G2           = '*'
+	ANSI_CMD_G3           = '+'
+	ANSI_CMD_DECPNM       = '>'
+	ANSI_CMD_DECPAM       = '='
+	ANSI_CMD_OSC          = ']'
+	ANSI_CMD_STR_TERM     = '\\'
+
+	KEY_CONTROL_PARAM_2 = ";2"
+	KEY_CONTROL_PARAM_3 = ";3"
+	KEY_CONTROL_PARAM_4 = ";4"
+	KEY_CONTROL_PARAM_5 = ";5"
+	KEY_CONTROL_PARAM_6 = ";6"
+	KEY_CONTROL_PARAM_7 = ";7"
+	KEY_CONTROL_PARAM_8 = ";8"
+	KEY_ESC_CSI         = "\x1B["
+	KEY_ESC_N           = "\x1BN"
+	KEY_ESC_O           = "\x1BO"
+
+	FILL_CHARACTER = ' '
+)
+
+func getByteRange(start byte, end byte) []byte {
+	bytes := make([]byte, 0, 32)
+	for i := start; i <= end; i++ {
+		bytes = append(bytes, byte(i))
+	}
+
+	return bytes
+}
+
+var toGroundBytes = getToGroundBytes()
+var executors = getExecuteBytes()
+
+// SPACE		  20+A0 hex  Always and everywhere a blank space
+// Intermediate	  20-2F hex   !"#$%&'()*+,-./
+var intermeds = getByteRange(0x20, 0x2F)
+
+// Parameters	  30-3F hex  0123456789:;<=>?
+// CSI Parameters 30-39, 3B hex 0123456789;
+var csiParams = getByteRange(0x30, 0x3F)
+
+var csiCollectables = append(getByteRange(0x30, 0x39), getByteRange(0x3B, 0x3F)...)
+
+// Uppercase	  40-5F hex  @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
+var upperCase = getByteRange(0x40, 0x5F)
+
+// Lowercase	  60-7E hex  `abcdefghijlkmnopqrstuvwxyz{|}~
+var lowerCase = getByteRange(0x60, 0x7E)
+
+// Alphabetics	  40-7E hex  (all of upper and lower case)
+var alphabetics = append(upperCase, lowerCase...)
+
+var printables = getByteRange(0x20, 0x7F)
+
+var escapeIntermediateToGroundBytes = getByteRange(0x30, 0x7E)
+var escapeToGroundBytes = getEscapeToGroundBytes()
+
+// See http://www.vt100.net/emu/vt500_parser.png for description of the complex
+// byte ranges below
+
+func getEscapeToGroundBytes() []byte {
+	escapeToGroundBytes := getByteRange(0x30, 0x4F)
+	escapeToGroundBytes = append(escapeToGroundBytes, getByteRange(0x51, 0x57)...)
+	escapeToGroundBytes = append(escapeToGroundBytes, 0x59)
+	escapeToGroundBytes = append(escapeToGroundBytes, 0x5A)
+	escapeToGroundBytes = append(escapeToGroundBytes, 0x5C)
+	escapeToGroundBytes = append(escapeToGroundBytes, getByteRange(0x60, 0x7E)...)
+	return escapeToGroundBytes
+}
+
+func getExecuteBytes() []byte {
+	executeBytes := getByteRange(0x00, 0x17)
+	executeBytes = append(executeBytes, 0x19)
+	executeBytes = append(executeBytes, getByteRange(0x1C, 0x1F)...)
+	return executeBytes
+}
+
+func getToGroundBytes() []byte {
+	groundBytes := []byte{0x18}
+	groundBytes = append(groundBytes, 0x1A)
+	groundBytes = append(groundBytes, getByteRange(0x80, 0x8F)...)
+	groundBytes = append(groundBytes, getByteRange(0x91, 0x97)...)
+	groundBytes = append(groundBytes, 0x99)
+	groundBytes = append(groundBytes, 0x9A)
+	groundBytes = append(groundBytes, 0x9C)
+	return groundBytes
+}
+
+// Delete		     7F hex  Always and everywhere ignored
+// C1 Control	  80-9F hex  32 additional control characters
+// G1 Displayable A1-FE hex  94 additional displayable characters
+// Special		  A0+FF hex  Same as SPACE and DELETE
@@ -0,0 +1,7 @@
+package ansiterm
+
+type ansiContext struct {
+	currentChar byte
+	paramBuffer []byte
+	interBuffer []byte
+}
@@ -0,0 +1,49 @@
+package ansiterm
+
+type csiEntryState struct {
+	baseState
+}
+
+func (csiState csiEntryState) Handle(b byte) (s state, e error) {
+	csiState.parser.logf("CsiEntry::Handle %#x", b)
+
+	nextState, err := csiState.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	switch {
+	case sliceContains(alphabetics, b):
+		return csiState.parser.ground, nil
+	case sliceContains(csiCollectables, b):
+		return csiState.parser.csiParam, nil
+	case sliceContains(executors, b):
+		return csiState, csiState.parser.execute()
+	}
+
+	return csiState, nil
+}
+
+func (csiState csiEntryState) Transition(s state) error {
+	csiState.parser.logf("CsiEntry::Transition %s --> %s", csiState.Name(), s.Name())
+	csiState.baseState.Transition(s)
+
+	switch s {
+	case csiState.parser.ground:
+		return csiState.parser.csiDispatch()
+	case csiState.parser.csiParam:
+		switch {
+		case sliceContains(csiParams, csiState.parser.context.currentChar):
+			csiState.parser.collectParam()
+		case sliceContains(intermeds, csiState.parser.context.currentChar):
+			csiState.parser.collectInter()
+		}
+	}
+
+	return nil
+}
+
+func (csiState csiEntryState) Enter() error {
+	csiState.parser.clear()
+	return nil
+}
@@ -0,0 +1,38 @@
+package ansiterm
+
+type csiParamState struct {
+	baseState
+}
+
+func (csiState csiParamState) Handle(b byte) (s state, e error) {
+	csiState.parser.logf("CsiParam::Handle %#x", b)
+
+	nextState, err := csiState.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	switch {
+	case sliceContains(alphabetics, b):
+		return csiState.parser.ground, nil
+	case sliceContains(csiCollectables, b):
+		csiState.parser.collectParam()
+		return csiState, nil
+	case sliceContains(executors, b):
+		return csiState, csiState.parser.execute()
+	}
+
+	return csiState, nil
+}
+
+func (csiState csiParamState) Transition(s state) error {
+	csiState.parser.logf("CsiParam::Transition %s --> %s", csiState.Name(), s.Name())
+	csiState.baseState.Transition(s)
+
+	switch s {
+	case csiState.parser.ground:
+		return csiState.parser.csiDispatch()
+	}
+
+	return nil
+}
@@ -0,0 +1,36 @@
+package ansiterm
+
+type escapeIntermediateState struct {
+	baseState
+}
+
+func (escState escapeIntermediateState) Handle(b byte) (s state, e error) {
+	escState.parser.logf("escapeIntermediateState::Handle %#x", b)
+	nextState, err := escState.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	switch {
+	case sliceContains(intermeds, b):
+		return escState, escState.parser.collectInter()
+	case sliceContains(executors, b):
+		return escState, escState.parser.execute()
+	case sliceContains(escapeIntermediateToGroundBytes, b):
+		return escState.parser.ground, nil
+	}
+
+	return escState, nil
+}
+
+func (escState escapeIntermediateState) Transition(s state) error {
+	escState.parser.logf("escapeIntermediateState::Transition %s --> %s", escState.Name(), s.Name())
+	escState.baseState.Transition(s)
+
+	switch s {
+	case escState.parser.ground:
+		return escState.parser.escDispatch()
+	}
+
+	return nil
+}
@@ -0,0 +1,47 @@
+package ansiterm
+
+type escapeState struct {
+	baseState
+}
+
+func (escState escapeState) Handle(b byte) (s state, e error) {
+	escState.parser.logf("escapeState::Handle %#x", b)
+	nextState, err := escState.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	switch {
+	case b == ANSI_ESCAPE_SECONDARY:
+		return escState.parser.csiEntry, nil
+	case b == ANSI_OSC_STRING_ENTRY:
+		return escState.parser.oscString, nil
+	case sliceContains(executors, b):
+		return escState, escState.parser.execute()
+	case sliceContains(escapeToGroundBytes, b):
+		return escState.parser.ground, nil
+	case sliceContains(intermeds, b):
+		return escState.parser.escapeIntermediate, nil
+	}
+
+	return escState, nil
+}
+
+func (escState escapeState) Transition(s state) error {
+	escState.parser.logf("Escape::Transition %s --> %s", escState.Name(), s.Name())
+	escState.baseState.Transition(s)
+
+	switch s {
+	case escState.parser.ground:
+		return escState.parser.escDispatch()
+	case escState.parser.escapeIntermediate:
+		return escState.parser.collectInter()
+	}
+
+	return nil
+}
+
+func (escState escapeState) Enter() error {
+	escState.parser.clear()
+	return nil
+}
@@ -0,0 +1,90 @@
+package ansiterm
+
+type AnsiEventHandler interface {
+	// Print
+	Print(b byte) error
+
+	// Execute C0 commands
+	Execute(b byte) error
+
+	// CUrsor Up
+	CUU(int) error
+
+	// CUrsor Down
+	CUD(int) error
+
+	// CUrsor Forward
+	CUF(int) error
+
+	// CUrsor Backward
+	CUB(int) error
+
+	// Cursor to Next Line
+	CNL(int) error
+
+	// Cursor to Previous Line
+	CPL(int) error
+
+	// Cursor Horizontal position Absolute
+	CHA(int) error
+
+	// Vertical line Position Absolute
+	VPA(int) error
+
+	// CUrsor Position
+	CUP(int, int) error
+
+	// Horizontal and Vertical Position (depends on PUM)
+	HVP(int, int) error
+
+	// Text Cursor Enable Mode
+	DECTCEM(bool) error
+
+	// Origin Mode
+	DECOM(bool) error
+
+	// 132 Column Mode
+	DECCOLM(bool) error
+
+	// Erase in Display
+	ED(int) error
+
+	// Erase in Line
+	EL(int) error
+
+	// Insert Line
+	IL(int) error
+
+	// Delete Line
+	DL(int) error
+
+	// Insert Character
+	ICH(int) error
+
+	// Delete Character
+	DCH(int) error
+
+	// Set Graphics Rendition
+	SGR([]int) error
+
+	// Pan Down
+	SU(int) error
+
+	// Pan Up
+	SD(int) error
+
+	// Device Attributes
+	DA([]string) error
+
+	// Set Top and Bottom Margins
+	DECSTBM(int, int) error
+
+	// Index
+	IND() error
+
+	// Reverse Index
+	RI() error
+
+	// Flush updates from previous commands
+	Flush() error
+}
@@ -0,0 +1,24 @@
+package ansiterm
+
+type groundState struct {
+	baseState
+}
+
+func (gs groundState) Handle(b byte) (s state, e error) {
+	gs.parser.context.currentChar = b
+
+	nextState, err := gs.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	switch {
+	case sliceContains(printables, b):
+		return gs, gs.parser.print()
+
+	case sliceContains(executors, b):
+		return gs, gs.parser.execute()
+	}
+
+	return gs, nil
+}
@@ -0,0 +1,23 @@
+package ansiterm
+
+type oscStringState struct {
+	baseState
+}
+
+func (oscState oscStringState) Handle(b byte) (s state, e error) {
+	oscState.parser.logf("OscString::Handle %#x", b)
+	nextState, err := oscState.baseState.Handle(b)
+	if nextState != nil || err != nil {
+		return nextState, err
+	}
+
+	// There are several control characters and sequences which can
+	// terminate an OSC string. Most of them are handled by the baseState
+	// handler. The ANSI_BEL character is a special case which behaves as a
+	// terminator only for an OSC string.
+	if b == ANSI_BEL {
+		return oscState.parser.ground, nil
+	}
+
+	return oscState, nil
+}
@@ -0,0 +1,151 @@
+package ansiterm
+
+import (
+	"errors"
+	"log"
+	"os"
+)
+
+type AnsiParser struct {
+	currState          state
+	eventHandler       AnsiEventHandler
+	context            *ansiContext
+	csiEntry           state
+	csiParam           state
+	dcsEntry           state
+	escape             state
+	escapeIntermediate state
+	error              state
+	ground             state
+	oscString          state
+	stateMap           []state
+
+	logf func(string, ...interface{})
+}
+
+type Option func(*AnsiParser)
+
+func WithLogf(f func(string, ...interface{})) Option {
+	return func(ap *AnsiParser) {
+		ap.logf = f
+	}
+}
+
+func CreateParser(initialState string, evtHandler AnsiEventHandler, opts ...Option) *AnsiParser {
+	ap := &AnsiParser{
+		eventHandler: evtHandler,
+		context:      &ansiContext{},
+	}
+	for _, o := range opts {
+		o(ap)
+	}
+
+	if isDebugEnv := os.Getenv(LogEnv); isDebugEnv == "1" {
+		logFile, _ := os.Create("ansiParser.log")
+		logger := log.New(logFile, "", log.LstdFlags)
+		if ap.logf != nil {
+			l := ap.logf
+			ap.logf = func(s string, v ...interface{}) {
+				l(s, v...)
+				logger.Printf(s, v...)
+			}
+		} else {
+			ap.logf = logger.Printf
+		}
+	}
+
+	if ap.logf == nil {
+		ap.logf = func(string, ...interface{}) {}
+	}
+
+	ap.csiEntry = csiEntryState{baseState{name: "CsiEntry", parser: ap}}
+	ap.csiParam = csiParamState{baseState{name: "CsiParam", parser: ap}}
+	ap.dcsEntry = dcsEntryState{baseState{name: "DcsEntry", parser: ap}}
+	ap.escape = escapeState{baseState{name: "Escape", parser: ap}}
+	ap.escapeIntermediate = escapeIntermediateState{baseState{name: "EscapeIntermediate", parser: ap}}
+	ap.error = errorState{baseState{name: "Error", parser: ap}}
+	ap.ground = groundState{baseState{name: "Ground", parser: ap}}
+	ap.oscString = oscStringState{baseState{name: "OscString", parser: ap}}
+
+	ap.stateMap = []state{
+		ap.csiEntry,
+		ap.csiParam,
+		ap.dcsEntry,
+		ap.escape,
+		ap.escapeIntermediate,
+		ap.error,
+		ap.ground,
+		ap.oscString,
+	}
+
+	ap.currState = getState(initialState, ap.stateMap)
+
+	ap.logf("CreateParser: parser %p", ap)
+	return ap
+}
+
+func getState(name string, states []state) state {
+	for _, el := range states {
+		if el.Name() == name {
+			return el
+		}
+	}
+
+	return nil
+}
+
+func (ap *AnsiParser) Parse(bytes []byte) (int, error) {
+	for i, b := range bytes {
+		if err := ap.handle(b); err != nil {
+			return i, err
+		}
+	}
+
+	return len(bytes), ap.eventHandler.Flush()
+}
+
+func (ap *AnsiParser) handle(b byte) error {
+	ap.context.currentChar = b
+	newState, err := ap.currState.Handle(b)
+	if err != nil {
+		return err
+	}
+
+	if newState == nil {
+		ap.logf("WARNING: newState is nil")
+		return errors.New("New state of 'nil' is invalid.")
+	}
+
+	if newState != ap.currState {
+		if err := ap.changeState(newState); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (ap *AnsiParser) changeState(newState state) error {
+	ap.logf("ChangeState %s --> %s", ap.currState.Name(), newState.Name())
+
+	// Exit old state
+	if err := ap.currState.Exit(); err != nil {
+		ap.logf("Exit state '%s' failed with : '%v'", ap.currState.Name(), err)
+		return err
+	}
+
+	// Perform transition action
+	if err := ap.currState.Transition(newState); err != nil {
+		ap.logf("Transition from '%s' to '%s' failed with: '%v'", ap.currState.Name(), newState.Name, err)
+		return err
+	}
+
+	// Enter new state
+	if err := newState.Enter(); err != nil {
+		ap.logf("Enter state '%s' failed with: '%v'", newState.Name(), err)
+		return err
+	}
+
+	ap.currState = newState
+	return nil
+}
@@ -0,0 +1,99 @@
+package ansiterm
+
+import (
+	"strconv"
+)
+
+func parseParams(bytes []byte) ([]string, error) {
+	paramBuff := make([]byte, 0, 0)
+	params := []string{}
+
+	for _, v := range bytes {
+		if v == ';' {
+			if len(paramBuff) > 0 {
+				// Completed parameter, append it to the list
+				s := string(paramBuff)
+				params = append(params, s)
+				paramBuff = make([]byte, 0, 0)
+			}
+		} else {
+			paramBuff = append(paramBuff, v)
+		}
+	}
+
+	// Last parameter may not be terminated with ';'
+	if len(paramBuff) > 0 {
+		s := string(paramBuff)
+		params = append(params, s)
+	}
+
+	return params, nil
+}
+
+func parseCmd(context ansiContext) (string, error) {
+	return string(context.currentChar), nil
+}
+
+func getInt(params []string, dflt int) int {
+	i := getInts(params, 1, dflt)[0]
+	return i
+}
+
+func getInts(params []string, minCount int, dflt int) []int {
+	ints := []int{}
+
+	for _, v := range params {
+		i, _ := strconv.Atoi(v)
+		// Zero is mapped to the default value in VT100.
+		if i == 0 {
+			i = dflt
+		}
+		ints = append(ints, i)
+	}
+
+	if len(ints) < minCount {
+		remaining := minCount - len(ints)
+		for i := 0; i < remaining; i++ {
+			ints = append(ints, dflt)
+		}
+	}
+
+	return ints
+}
+
+func (ap *AnsiParser) modeDispatch(param string, set bool) error {
+	switch param {
+	case "?3":
+		return ap.eventHandler.DECCOLM(set)
+	case "?6":
+		return ap.eventHandler.DECOM(set)
+	case "?25":
+		return ap.eventHandler.DECTCEM(set)
+	}
+	return nil
+}
+
+func (ap *AnsiParser) hDispatch(params []string) error {
+	if len(params) == 1 {
+		return ap.modeDispatch(params[0], true)
+	}
+
+	return nil
+}
+
+func (ap *AnsiParser) lDispatch(params []string) error {
+	if len(params) == 1 {
+		return ap.modeDispatch(params[0], false)
+	}
+
+	return nil
+}
+
+func getEraseParam(params []string) int {
+	param := getInt(params, 0)
+	if param < 0 || 3 < param {
+		param = 0
+	}
+
+	return param
+}
@@ -0,0 +1,119 @@
+package ansiterm
+
+func (ap *AnsiParser) collectParam() error {
+	currChar := ap.context.currentChar
+	ap.logf("collectParam %#x", currChar)
+	ap.context.paramBuffer = append(ap.context.paramBuffer, currChar)
+	return nil
+}
+
+func (ap *AnsiParser) collectInter() error {
+	currChar := ap.context.currentChar
+	ap.logf("collectInter %#x", currChar)
+	ap.context.paramBuffer = append(ap.context.interBuffer, currChar)
+	return nil
+}
+
+func (ap *AnsiParser) escDispatch() error {
+	cmd, _ := parseCmd(*ap.context)
+	intermeds := ap.context.interBuffer
+	ap.logf("escDispatch currentChar: %#x", ap.context.currentChar)
+	ap.logf("escDispatch: %v(%v)", cmd, intermeds)
+
+	switch cmd {
+	case "D": // IND
+		return ap.eventHandler.IND()
+	case "E": // NEL, equivalent to CRLF
+		err := ap.eventHandler.Execute(ANSI_CARRIAGE_RETURN)
+		if err == nil {
+			err = ap.eventHandler.Execute(ANSI_LINE_FEED)
+		}
+		return err
+	case "M": // RI
+		return ap.eventHandler.RI()
+	}
+
+	return nil
+}
+
+func (ap *AnsiParser) csiDispatch() error {
+	cmd, _ := parseCmd(*ap.context)
+	params, _ := parseParams(ap.context.paramBuffer)
+	ap.logf("Parsed params: %v with length: %d", params, len(params))
+
+	ap.logf("csiDispatch: %v(%v)", cmd, params)
+
+	switch cmd {
+	case "@":
+		return ap.eventHandler.ICH(getInt(params, 1))
+	case "A":
+		return ap.eventHandler.CUU(getInt(params, 1))
+	case "B":
+		return ap.eventHandler.CUD(getInt(params, 1))
+	case "C":
+		return ap.eventHandler.CUF(getInt(params, 1))
+	case "D":
+		return ap.eventHandler.CUB(getInt(params, 1))
+	case "E":
+		return ap.eventHandler.CNL(getInt(params, 1))
+	case "F":
+		return ap.eventHandler.CPL(getInt(params, 1))
+	case "G":
+		return ap.eventHandler.CHA(getInt(params, 1))
+	case "H":
+		ints := getInts(params, 2, 1)
+		x, y := ints[0], ints[1]
+		return ap.eventHandler.CUP(x, y)
+	case "J":
+		param := getEraseParam(params)
+		return ap.eventHandler.ED(param)
+	case "K":
+		param := getEraseParam(params)
+		return ap.eventHandler.EL(param)
+	case "L":
+		return ap.eventHandler.IL(getInt(params, 1))
+	case "M":
+		return ap.eventHandler.DL(getInt(params, 1))
+	case "P":
+		return ap.eventHandler.DCH(getInt(params, 1))
+	case "S":
+		return ap.eventHandler.SU(getInt(params, 1))
+	case "T":
+		return ap.eventHandler.SD(getInt(params, 1))
+	case "c":
+		return ap.eventHandler.DA(params)
+	case "d":
+		return ap.eventHandler.VPA(getInt(params, 1))
+	case "f":
+		ints := getInts(params, 2, 1)
+		x, y := ints[0], ints[1]
+		return ap.eventHandler.HVP(x, y)
+	case "h":
+		return ap.hDispatch(params)
+	case "l":
+		return ap.lDispatch(params)
+	case "m":
+		return ap.eventHandler.SGR(getInts(params, 1, 0))
+	case "r":
+		ints := getInts(params, 2, 1)
+		top, bottom := ints[0], ints[1]
+		return ap.eventHandler.DECSTBM(top, bottom)
+	default:
+		ap.logf("ERROR: Unsupported CSI command: '%s', with full context:  %v", cmd, ap.context)
+		return nil
+	}
+
+}
+
+func (ap *AnsiParser) print() error {
+	return ap.eventHandler.Print(ap.context.currentChar)
+}
+
+func (ap *AnsiParser) clear() error {
+	ap.context = &ansiContext{}
+	return nil
+}
+
+func (ap *AnsiParser) execute() error {
+	return ap.eventHandler.Execute(ap.context.currentChar)
+}
@@ -0,0 +1,71 @@
+package ansiterm
+
+type stateID int
+
+type state interface {
+	Enter() error
+	Exit() error
+	Handle(byte) (state, error)
+	Name() string
+	Transition(state) error
+}
+
+type baseState struct {
+	name   string
+	parser *AnsiParser
+}
+
+func (base baseState) Enter() error {
+	return nil
+}
+
+func (base baseState) Exit() error {
+	return nil
+}
+
+func (base baseState) Handle(b byte) (s state, e error) {
+
+	switch {
+	case b == CSI_ENTRY:
+		return base.parser.csiEntry, nil
+	case b == DCS_ENTRY:
+		return base.parser.dcsEntry, nil
+	case b == ANSI_ESCAPE_PRIMARY:
+		return base.parser.escape, nil
+	case b == OSC_STRING:
+		return base.parser.oscString, nil
+	case sliceContains(toGroundBytes, b):
+		return base.parser.ground, nil
+	}
+
+	return nil, nil
+}
+
+func (base baseState) Name() string {
+	return base.name
+}
+
+func (base baseState) Transition(s state) error {
+	if s == base.parser.ground {
+		execBytes := []byte{0x18}
+		execBytes = append(execBytes, 0x1A)
+		execBytes = append(execBytes, getByteRange(0x80, 0x8F)...)
+		execBytes = append(execBytes, getByteRange(0x91, 0x97)...)
+		execBytes = append(execBytes, 0x99)
+		execBytes = append(execBytes, 0x9A)
+
+		if sliceContains(execBytes, base.parser.context.currentChar) {
+			return base.parser.execute()
+		}
+	}
+
+	return nil
+}
+
+type dcsEntryState struct {
+	baseState
+}
+
+type errorState struct {
+	baseState
+}
@@ -0,0 +1,21 @@
+package ansiterm
+
+import (
+	"strconv"
+)
+
+func sliceContains(bytes []byte, b byte) bool {
+	for _, v := range bytes {
+		if v == b {
+			return true
+		}
+	}
+
+	return false
+}
+
+func convertBytesToInteger(bytes []byte) int {
+	s := string(bytes)
+	i, _ := strconv.Atoi(s)
+	return i
+}
@@ -0,0 +1,196 @@
+// +build windows
+
+package winterm
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"github.com/Azure/go-ansiterm"
+	windows "golang.org/x/sys/windows"
+)
+
+// Windows keyboard constants
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/dd375731(v=vs.85).aspx.
+const (
+	VK_PRIOR    = 0x21 // PAGE UP key
+	VK_NEXT     = 0x22 // PAGE DOWN key
+	VK_END      = 0x23 // END key
+	VK_HOME     = 0x24 // HOME key
+	VK_LEFT     = 0x25 // LEFT ARROW key
+	VK_UP       = 0x26 // UP ARROW key
+	VK_RIGHT    = 0x27 // RIGHT ARROW key
+	VK_DOWN     = 0x28 // DOWN ARROW key
+	VK_SELECT   = 0x29 // SELECT key
+	VK_PRINT    = 0x2A // PRINT key
+	VK_EXECUTE  = 0x2B // EXECUTE key
+	VK_SNAPSHOT = 0x2C // PRINT SCREEN key
+	VK_INSERT   = 0x2D // INS key
+	VK_DELETE   = 0x2E // DEL key
+	VK_HELP     = 0x2F // HELP key
+	VK_F1       = 0x70 // F1 key
+	VK_F2       = 0x71 // F2 key
+	VK_F3       = 0x72 // F3 key
+	VK_F4       = 0x73 // F4 key
+	VK_F5       = 0x74 // F5 key
+	VK_F6       = 0x75 // F6 key
+	VK_F7       = 0x76 // F7 key
+	VK_F8       = 0x77 // F8 key
+	VK_F9       = 0x78 // F9 key
+	VK_F10      = 0x79 // F10 key
+	VK_F11      = 0x7A // F11 key
+	VK_F12      = 0x7B // F12 key
+
+	RIGHT_ALT_PRESSED  = 0x0001
+	LEFT_ALT_PRESSED   = 0x0002
+	RIGHT_CTRL_PRESSED = 0x0004
+	LEFT_CTRL_PRESSED  = 0x0008
+	SHIFT_PRESSED      = 0x0010
+	NUMLOCK_ON         = 0x0020
+	SCROLLLOCK_ON      = 0x0040
+	CAPSLOCK_ON        = 0x0080
+	ENHANCED_KEY       = 0x0100
+)
+
+type ansiCommand struct {
+	CommandBytes []byte
+	Command      string
+	Parameters   []string
+	IsSpecial    bool
+}
+
+func newAnsiCommand(command []byte) *ansiCommand {
+
+	if isCharacterSelectionCmdChar(command[1]) {
+		// Is Character Set Selection commands
+		return &ansiCommand{
+			CommandBytes: command,
+			Command:      string(command),
+			IsSpecial:    true,
+		}
+	}
+
+	// last char is command character
+	lastCharIndex := len(command) - 1
+
+	ac := &ansiCommand{
+		CommandBytes: command,
+		Command:      string(command[lastCharIndex]),
+		IsSpecial:    false,
+	}
+
+	// more than a single escape
+	if lastCharIndex != 0 {
+		start := 1
+		// skip if double char escape sequence
+		if command[0] == ansiterm.ANSI_ESCAPE_PRIMARY && command[1] == ansiterm.ANSI_ESCAPE_SECONDARY {
+			start++
+		}
+		// convert this to GetNextParam method
+		ac.Parameters = strings.Split(string(command[start:lastCharIndex]), ansiterm.ANSI_PARAMETER_SEP)
+	}
+
+	return ac
+}
+
+func (ac *ansiCommand) paramAsSHORT(index int, defaultValue int16) int16 {
+	if index < 0 || index >= len(ac.Parameters) {
+		return defaultValue
+	}
+
+	param, err := strconv.ParseInt(ac.Parameters[index], 10, 16)
+	if err != nil {
+		return defaultValue
+	}
+
+	return int16(param)
+}
+
+func (ac *ansiCommand) String() string {
+	return fmt.Sprintf("0x%v \"%v\" (\"%v\")",
+		bytesToHex(ac.CommandBytes),
+		ac.Command,
+		strings.Join(ac.Parameters, "\",\""))
+}
+
+// isAnsiCommandChar returns true if the passed byte falls within the range of ANSI commands.
+// See http://manpages.ubuntu.com/manpages/intrepid/man4/console_codes.4.html.
+func isAnsiCommandChar(b byte) bool {
+	switch {
+	case ansiterm.ANSI_COMMAND_FIRST <= b && b <= ansiterm.ANSI_COMMAND_LAST && b != ansiterm.ANSI_ESCAPE_SECONDARY:
+		return true
+	case b == ansiterm.ANSI_CMD_G1 || b == ansiterm.ANSI_CMD_OSC || b == ansiterm.ANSI_CMD_DECPAM || b == ansiterm.ANSI_CMD_DECPNM:
+		// non-CSI escape sequence terminator
+		return true
+	case b == ansiterm.ANSI_CMD_STR_TERM || b == ansiterm.ANSI_BEL:
+		// String escape sequence terminator
+		return true
+	}
+	return false
+}
+
+func isXtermOscSequence(command []byte, current byte) bool {
+	return (len(command) >= 2 && command[0] == ansiterm.ANSI_ESCAPE_PRIMARY && command[1] == ansiterm.ANSI_CMD_OSC && current != ansiterm.ANSI_BEL)
+}
+
+func isCharacterSelectionCmdChar(b byte) bool {
+	return (b == ansiterm.ANSI_CMD_G0 || b == ansiterm.ANSI_CMD_G1 || b == ansiterm.ANSI_CMD_G2 || b == ansiterm.ANSI_CMD_G3)
+}
+
+// bytesToHex converts a slice of bytes to a human-readable string.
+func bytesToHex(b []byte) string {
+	hex := make([]string, len(b))
+	for i, ch := range b {
+		hex[i] = fmt.Sprintf("%X", ch)
+	}
+	return strings.Join(hex, "")
+}
+
+// ensureInRange adjusts the passed value, if necessary, to ensure it is within
+// the passed min / max range.
+func ensureInRange(n int16, min int16, max int16) int16 {
+	if n < min {
+		return min
+	} else if n > max {
+		return max
+	} else {
+		return n
+	}
+}
+
+func GetStdFile(nFile int) (*os.File, uintptr) {
+	var file *os.File
+
+	// syscall uses negative numbers
+	// windows package uses very big uint32
+	// Keep these switches split so we don't have to convert ints too much.
+	switch uint32(nFile) {
+	case windows.STD_INPUT_HANDLE:
+		file = os.Stdin
+	case windows.STD_OUTPUT_HANDLE:
+		file = os.Stdout
+	case windows.STD_ERROR_HANDLE:
+		file = os.Stderr
+	default:
+		switch nFile {
+		case syscall.STD_INPUT_HANDLE:
+			file = os.Stdin
+		case syscall.STD_OUTPUT_HANDLE:
+			file = os.Stdout
+		case syscall.STD_ERROR_HANDLE:
+			file = os.Stderr
+		default:
+			panic(fmt.Errorf("Invalid standard handle identifier: %v", nFile))
+		}
+	}
+
+	fd, err := syscall.GetStdHandle(nFile)
+	if err != nil {
+		panic(fmt.Errorf("Invalid standard handle identifier: %v -- %v", nFile, err))
+	}
+
+	return file, uintptr(fd)
+}
@@ -0,0 +1,327 @@
+// +build windows
+
+package winterm
+
+import (
+	"fmt"
+	"syscall"
+	"unsafe"
+)
+
+//===========================================================================================================
+// IMPORTANT NOTE:
+//
+//	The methods below make extensive use of the "unsafe" package to obtain the required pointers.
+//	Beginning in Go 1.3, the garbage collector may release local variables (e.g., incoming arguments, stack
+//	variables) the pointers reference *before* the API completes.
+//
+//  As a result, in those cases, the code must hint that the variables remain in active by invoking the
+//	dummy method "use" (see below). Newer versions of Go are planned to change the mechanism to no longer
+//	require unsafe pointers.
+//
+//	If you add or modify methods, ENSURE protection of local variables through the "use" builtin to inform
+//	the garbage collector the variables remain in use if:
+//
+//	-- The value is not a pointer (e.g., int32, struct)
+//	-- The value is not referenced by the method after passing the pointer to Windows
+//
+//	See http://golang.org/doc/go1.3.
+//===========================================================================================================
+
+var (
+	kernel32DLL = syscall.NewLazyDLL("kernel32.dll")
+
+	getConsoleCursorInfoProc       = kernel32DLL.NewProc("GetConsoleCursorInfo")
+	setConsoleCursorInfoProc       = kernel32DLL.NewProc("SetConsoleCursorInfo")
+	setConsoleCursorPositionProc   = kernel32DLL.NewProc("SetConsoleCursorPosition")
+	setConsoleModeProc             = kernel32DLL.NewProc("SetConsoleMode")
+	getConsoleScreenBufferInfoProc = kernel32DLL.NewProc("GetConsoleScreenBufferInfo")
+	setConsoleScreenBufferSizeProc = kernel32DLL.NewProc("SetConsoleScreenBufferSize")
+	scrollConsoleScreenBufferProc  = kernel32DLL.NewProc("ScrollConsoleScreenBufferA")
+	setConsoleTextAttributeProc    = kernel32DLL.NewProc("SetConsoleTextAttribute")
+	setConsoleWindowInfoProc       = kernel32DLL.NewProc("SetConsoleWindowInfo")
+	writeConsoleOutputProc         = kernel32DLL.NewProc("WriteConsoleOutputW")
+	readConsoleInputProc           = kernel32DLL.NewProc("ReadConsoleInputW")
+	waitForSingleObjectProc        = kernel32DLL.NewProc("WaitForSingleObject")
+)
+
+// Windows Console constants
+const (
+	// Console modes
+	// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686033(v=vs.85).aspx.
+	ENABLE_PROCESSED_INPUT        = 0x0001
+	ENABLE_LINE_INPUT             = 0x0002
+	ENABLE_ECHO_INPUT             = 0x0004
+	ENABLE_WINDOW_INPUT           = 0x0008
+	ENABLE_MOUSE_INPUT            = 0x0010
+	ENABLE_INSERT_MODE            = 0x0020
+	ENABLE_QUICK_EDIT_MODE        = 0x0040
+	ENABLE_EXTENDED_FLAGS         = 0x0080
+	ENABLE_AUTO_POSITION          = 0x0100
+	ENABLE_VIRTUAL_TERMINAL_INPUT = 0x0200
+
+	ENABLE_PROCESSED_OUTPUT            = 0x0001
+	ENABLE_WRAP_AT_EOL_OUTPUT          = 0x0002
+	ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x0004
+	DISABLE_NEWLINE_AUTO_RETURN        = 0x0008
+	ENABLE_LVB_GRID_WORLDWIDE          = 0x0010
+
+	// Character attributes
+	// Note:
+	// -- The attributes are combined to produce various colors (e.g., Blue + Green will create Cyan).
+	//    Clearing all foreground or background colors results in black; setting all creates white.
+	// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms682088(v=vs.85).aspx#_win32_character_attributes.
+	FOREGROUND_BLUE      uint16 = 0x0001
+	FOREGROUND_GREEN     uint16 = 0x0002
+	FOREGROUND_RED       uint16 = 0x0004
+	FOREGROUND_INTENSITY uint16 = 0x0008
+	FOREGROUND_MASK      uint16 = 0x000F
+
+	BACKGROUND_BLUE      uint16 = 0x0010
+	BACKGROUND_GREEN     uint16 = 0x0020
+	BACKGROUND_RED       uint16 = 0x0040
+	BACKGROUND_INTENSITY uint16 = 0x0080
+	BACKGROUND_MASK      uint16 = 0x00F0
+
+	COMMON_LVB_MASK          uint16 = 0xFF00
+	COMMON_LVB_REVERSE_VIDEO uint16 = 0x4000
+	COMMON_LVB_UNDERSCORE    uint16 = 0x8000
+
+	// Input event types
+	// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms683499(v=vs.85).aspx.
+	KEY_EVENT                = 0x0001
+	MOUSE_EVENT              = 0x0002
+	WINDOW_BUFFER_SIZE_EVENT = 0x0004
+	MENU_EVENT               = 0x0008
+	FOCUS_EVENT              = 0x0010
+
+	// WaitForSingleObject return codes
+	WAIT_ABANDONED = 0x00000080
+	WAIT_FAILED    = 0xFFFFFFFF
+	WAIT_SIGNALED  = 0x0000000
+	WAIT_TIMEOUT   = 0x00000102
+
+	// WaitForSingleObject wait duration
+	WAIT_INFINITE       = 0xFFFFFFFF
+	WAIT_ONE_SECOND     = 1000
+	WAIT_HALF_SECOND    = 500
+	WAIT_QUARTER_SECOND = 250
+)
+
+// Windows API Console types
+// -- See https://msdn.microsoft.com/en-us/library/windows/desktop/ms682101(v=vs.85).aspx for Console specific types (e.g., COORD)
+// -- See https://msdn.microsoft.com/en-us/library/aa296569(v=vs.60).aspx for comments on alignment
+type (
+	CHAR_INFO struct {
+		UnicodeChar uint16
+		Attributes  uint16
+	}
+
+	CONSOLE_CURSOR_INFO struct {
+		Size    uint32
+		Visible int32
+	}
+
+	CONSOLE_SCREEN_BUFFER_INFO struct {
+		Size              COORD
+		CursorPosition    COORD
+		Attributes        uint16
+		Window            SMALL_RECT
+		MaximumWindowSize COORD
+	}
+
+	COORD struct {
+		X int16
+		Y int16
+	}
+
+	SMALL_RECT struct {
+		Left   int16
+		Top    int16
+		Right  int16
+		Bottom int16
+	}
+
+	// INPUT_RECORD is a C/C++ union of which KEY_EVENT_RECORD is one case, it is also the largest
+	// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms683499(v=vs.85).aspx.
+	INPUT_RECORD struct {
+		EventType uint16
+		KeyEvent  KEY_EVENT_RECORD
+	}
+
+	KEY_EVENT_RECORD struct {
+		KeyDown         int32
+		RepeatCount     uint16
+		VirtualKeyCode  uint16
+		VirtualScanCode uint16
+		UnicodeChar     uint16
+		ControlKeyState uint32
+	}
+
+	WINDOW_BUFFER_SIZE struct {
+		Size COORD
+	}
+)
+
+// boolToBOOL converts a Go bool into a Windows int32.
+func boolToBOOL(f bool) int32 {
+	if f {
+		return int32(1)
+	} else {
+		return int32(0)
+	}
+}
+
+// GetConsoleCursorInfo retrieves information about the size and visiblity of the console cursor.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms683163(v=vs.85).aspx.
+func GetConsoleCursorInfo(handle uintptr, cursorInfo *CONSOLE_CURSOR_INFO) error {
+	r1, r2, err := getConsoleCursorInfoProc.Call(handle, uintptr(unsafe.Pointer(cursorInfo)), 0)
+	return checkError(r1, r2, err)
+}
+
+// SetConsoleCursorInfo sets the size and visiblity of the console cursor.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686019(v=vs.85).aspx.
+func SetConsoleCursorInfo(handle uintptr, cursorInfo *CONSOLE_CURSOR_INFO) error {
+	r1, r2, err := setConsoleCursorInfoProc.Call(handle, uintptr(unsafe.Pointer(cursorInfo)), 0)
+	return checkError(r1, r2, err)
+}
+
+// SetConsoleCursorPosition location of the console cursor.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686025(v=vs.85).aspx.
+func SetConsoleCursorPosition(handle uintptr, coord COORD) error {
+	r1, r2, err := setConsoleCursorPositionProc.Call(handle, coordToPointer(coord))
+	use(coord)
+	return checkError(r1, r2, err)
+}
+
+// GetConsoleMode gets the console mode for given file descriptor
+// See http://msdn.microsoft.com/en-us/library/windows/desktop/ms683167(v=vs.85).aspx.
+func GetConsoleMode(handle uintptr) (mode uint32, err error) {
+	err = syscall.GetConsoleMode(syscall.Handle(handle), &mode)
+	return mode, err
+}
+
+// SetConsoleMode sets the console mode for given file descriptor
+// See http://msdn.microsoft.com/en-us/library/windows/desktop/ms686033(v=vs.85).aspx.
+func SetConsoleMode(handle uintptr, mode uint32) error {
+	r1, r2, err := setConsoleModeProc.Call(handle, uintptr(mode), 0)
+	use(mode)
+	return checkError(r1, r2, err)
+}
+
+// GetConsoleScreenBufferInfo retrieves information about the specified console screen buffer.
+// See http://msdn.microsoft.com/en-us/library/windows/desktop/ms683171(v=vs.85).aspx.
+func GetConsoleScreenBufferInfo(handle uintptr) (*CONSOLE_SCREEN_BUFFER_INFO, error) {
+	info := CONSOLE_SCREEN_BUFFER_INFO{}
+	err := checkError(getConsoleScreenBufferInfoProc.Call(handle, uintptr(unsafe.Pointer(&info)), 0))
+	if err != nil {
+		return nil, err
+	}
+	return &info, nil
+}
+
+func ScrollConsoleScreenBuffer(handle uintptr, scrollRect SMALL_RECT, clipRect SMALL_RECT, destOrigin COORD, char CHAR_INFO) error {
+	r1, r2, err := scrollConsoleScreenBufferProc.Call(handle, uintptr(unsafe.Pointer(&scrollRect)), uintptr(unsafe.Pointer(&clipRect)), coordToPointer(destOrigin), uintptr(unsafe.Pointer(&char)))
+	use(scrollRect)
+	use(clipRect)
+	use(destOrigin)
+	use(char)
+	return checkError(r1, r2, err)
+}
+
+// SetConsoleScreenBufferSize sets the size of the console screen buffer.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686044(v=vs.85).aspx.
+func SetConsoleScreenBufferSize(handle uintptr, coord COORD) error {
+	r1, r2, err := setConsoleScreenBufferSizeProc.Call(handle, coordToPointer(coord))
+	use(coord)
+	return checkError(r1, r2, err)
+}
+
+// SetConsoleTextAttribute sets the attributes of characters written to the
+// console screen buffer by the WriteFile or WriteConsole function.
+// See http://msdn.microsoft.com/en-us/library/windows/desktop/ms686047(v=vs.85).aspx.
+func SetConsoleTextAttribute(handle uintptr, attribute uint16) error {
+	r1, r2, err := setConsoleTextAttributeProc.Call(handle, uintptr(attribute), 0)
+	use(attribute)
+	return checkError(r1, r2, err)
+}
+
+// SetConsoleWindowInfo sets the size and position of the console screen buffer's window.
+// Note that the size and location must be within and no larger than the backing console screen buffer.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686125(v=vs.85).aspx.
+func SetConsoleWindowInfo(handle uintptr, isAbsolute bool, rect SMALL_RECT) error {
+	r1, r2, err := setConsoleWindowInfoProc.Call(handle, uintptr(boolToBOOL(isAbsolute)), uintptr(unsafe.Pointer(&rect)))
+	use(isAbsolute)
+	use(rect)
+	return checkError(r1, r2, err)
+}
+
+// WriteConsoleOutput writes the CHAR_INFOs from the provided buffer to the active console buffer.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms687404(v=vs.85).aspx.
+func WriteConsoleOutput(handle uintptr, buffer []CHAR_INFO, bufferSize COORD, bufferCoord COORD, writeRegion *SMALL_RECT) error {
+	r1, r2, err := writeConsoleOutputProc.Call(handle, uintptr(unsafe.Pointer(&buffer[0])), coordToPointer(bufferSize), coordToPointer(bufferCoord), uintptr(unsafe.Pointer(writeRegion)))
+	use(buffer)
+	use(bufferSize)
+	use(bufferCoord)
+	return checkError(r1, r2, err)
+}
+
+// ReadConsoleInput reads (and removes) data from the console input buffer.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms684961(v=vs.85).aspx.
+func ReadConsoleInput(handle uintptr, buffer []INPUT_RECORD, count *uint32) error {
+	r1, r2, err := readConsoleInputProc.Call(handle, uintptr(unsafe.Pointer(&buffer[0])), uintptr(len(buffer)), uintptr(unsafe.Pointer(count)))
+	use(buffer)
+	return checkError(r1, r2, err)
+}
+
+// WaitForSingleObject waits for the passed handle to be signaled.
+// It returns true if the handle was signaled; false otherwise.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms687032(v=vs.85).aspx.
+func WaitForSingleObject(handle uintptr, msWait uint32) (bool, error) {
+	r1, _, err := waitForSingleObjectProc.Call(handle, uintptr(uint32(msWait)))
+	switch r1 {
+	case WAIT_ABANDONED, WAIT_TIMEOUT:
+		return false, nil
+	case WAIT_SIGNALED:
+		return true, nil
+	}
+	use(msWait)
+	return false, err
+}
+
+// String helpers
+func (info CONSOLE_SCREEN_BUFFER_INFO) String() string {
+	return fmt.Sprintf("Size(%v) Cursor(%v) Window(%v) Max(%v)", info.Size, info.CursorPosition, info.Window, info.MaximumWindowSize)
+}
+
+func (coord COORD) String() string {
+	return fmt.Sprintf("%v,%v", coord.X, coord.Y)
+}
+
+func (rect SMALL_RECT) String() string {
+	return fmt.Sprintf("(%v,%v),(%v,%v)", rect.Left, rect.Top, rect.Right, rect.Bottom)
+}
+
+// checkError evaluates the results of a Windows API call and returns the error if it failed.
+func checkError(r1, r2 uintptr, err error) error {
+	// Windows APIs return non-zero to indicate success
+	if r1 != 0 {
+		return nil
+	}
+
+	// Return the error if provided, otherwise default to EINVAL
+	if err != nil {
+		return err
+	}
+	return syscall.EINVAL
+}
+
+// coordToPointer converts a COORD into a uintptr (by fooling the type system).
+func coordToPointer(c COORD) uintptr {
+	// Note: This code assumes the two SHORTs are correctly laid out; the "cast" to uint32 is just to get a pointer to pass.
+	return uintptr(*((*uint32)(unsafe.Pointer(&c))))
+}
+
+// use is a no-op, but the compiler cannot see that it is.
+// Calling use(p) ensures that p is kept live until that point.
+func use(p interface{}) {}
@@ -0,0 +1,100 @@
+// +build windows
+
+package winterm
+
+import "github.com/Azure/go-ansiterm"
+
+const (
+	FOREGROUND_COLOR_MASK = FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE
+	BACKGROUND_COLOR_MASK = BACKGROUND_RED | BACKGROUND_GREEN | BACKGROUND_BLUE
+)
+
+// collectAnsiIntoWindowsAttributes modifies the passed Windows text mode flags to reflect the
+// request represented by the passed ANSI mode.
+func collectAnsiIntoWindowsAttributes(windowsMode uint16, inverted bool, baseMode uint16, ansiMode int16) (uint16, bool) {
+	switch ansiMode {
+
+	// Mode styles
+	case ansiterm.ANSI_SGR_BOLD:
+		windowsMode = windowsMode | FOREGROUND_INTENSITY
+
+	case ansiterm.ANSI_SGR_DIM, ansiterm.ANSI_SGR_BOLD_DIM_OFF:
+		windowsMode &^= FOREGROUND_INTENSITY
+
+	case ansiterm.ANSI_SGR_UNDERLINE:
+		windowsMode = windowsMode | COMMON_LVB_UNDERSCORE
+
+	case ansiterm.ANSI_SGR_REVERSE:
+		inverted = true
+
+	case ansiterm.ANSI_SGR_REVERSE_OFF:
+		inverted = false
+
+	case ansiterm.ANSI_SGR_UNDERLINE_OFF:
+		windowsMode &^= COMMON_LVB_UNDERSCORE
+
+		// Foreground colors
+	case ansiterm.ANSI_SGR_FOREGROUND_DEFAULT:
+		windowsMode = (windowsMode &^ FOREGROUND_MASK) | (baseMode & FOREGROUND_MASK)
+
+	case ansiterm.ANSI_SGR_FOREGROUND_BLACK:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK)
+
+	case ansiterm.ANSI_SGR_FOREGROUND_RED:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_RED
+
+	case ansiterm.ANSI_SGR_FOREGROUND_GREEN:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_GREEN
+
+	case ansiterm.ANSI_SGR_FOREGROUND_YELLOW:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_RED | FOREGROUND_GREEN
+
+	case ansiterm.ANSI_SGR_FOREGROUND_BLUE:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_BLUE
+
+	case ansiterm.ANSI_SGR_FOREGROUND_MAGENTA:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_RED | FOREGROUND_BLUE
+
+	case ansiterm.ANSI_SGR_FOREGROUND_CYAN:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_GREEN | FOREGROUND_BLUE
+
+	case ansiterm.ANSI_SGR_FOREGROUND_WHITE:
+		windowsMode = (windowsMode &^ FOREGROUND_COLOR_MASK) | FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE
+
+		// Background colors
+	case ansiterm.ANSI_SGR_BACKGROUND_DEFAULT:
+		// Black with no intensity
+		windowsMode = (windowsMode &^ BACKGROUND_MASK) | (baseMode & BACKGROUND_MASK)
+
+	case ansiterm.ANSI_SGR_BACKGROUND_BLACK:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK)
+
+	case ansiterm.ANSI_SGR_BACKGROUND_RED:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_RED
+
+	case ansiterm.ANSI_SGR_BACKGROUND_GREEN:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_GREEN
+
+	case ansiterm.ANSI_SGR_BACKGROUND_YELLOW:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_RED | BACKGROUND_GREEN
+
+	case ansiterm.ANSI_SGR_BACKGROUND_BLUE:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_BLUE
+
+	case ansiterm.ANSI_SGR_BACKGROUND_MAGENTA:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_RED | BACKGROUND_BLUE
+
+	case ansiterm.ANSI_SGR_BACKGROUND_CYAN:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_GREEN | BACKGROUND_BLUE
+
+	case ansiterm.ANSI_SGR_BACKGROUND_WHITE:
+		windowsMode = (windowsMode &^ BACKGROUND_COLOR_MASK) | BACKGROUND_RED | BACKGROUND_GREEN | BACKGROUND_BLUE
+	}
+
+	return windowsMode, inverted
+}
+
+// invertAttributes inverts the foreground and background colors of a Windows attributes value
+func invertAttributes(windowsMode uint16) uint16 {
+	return (COMMON_LVB_MASK & windowsMode) | ((FOREGROUND_MASK & windowsMode) << 4) | ((BACKGROUND_MASK & windowsMode) >> 4)
+}
@@ -0,0 +1,101 @@
+// +build windows
+
+package winterm
+
+const (
+	horizontal = iota
+	vertical
+)
+
+func (h *windowsAnsiEventHandler) getCursorWindow(info *CONSOLE_SCREEN_BUFFER_INFO) SMALL_RECT {
+	if h.originMode {
+		sr := h.effectiveSr(info.Window)
+		return SMALL_RECT{
+			Top:    sr.top,
+			Bottom: sr.bottom,
+			Left:   0,
+			Right:  info.Size.X - 1,
+		}
+	} else {
+		return SMALL_RECT{
+			Top:    info.Window.Top,
+			Bottom: info.Window.Bottom,
+			Left:   0,
+			Right:  info.Size.X - 1,
+		}
+	}
+}
+
+// setCursorPosition sets the cursor to the specified position, bounded to the screen size
+func (h *windowsAnsiEventHandler) setCursorPosition(position COORD, window SMALL_RECT) error {
+	position.X = ensureInRange(position.X, window.Left, window.Right)
+	position.Y = ensureInRange(position.Y, window.Top, window.Bottom)
+	err := SetConsoleCursorPosition(h.fd, position)
+	if err != nil {
+		return err
+	}
+	h.logf("Cursor position set: (%d, %d)", position.X, position.Y)
+	return err
+}
+
+func (h *windowsAnsiEventHandler) moveCursorVertical(param int) error {
+	return h.moveCursor(vertical, param)
+}
+
+func (h *windowsAnsiEventHandler) moveCursorHorizontal(param int) error {
+	return h.moveCursor(horizontal, param)
+}
+
+func (h *windowsAnsiEventHandler) moveCursor(moveMode int, param int) error {
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	position := info.CursorPosition
+	switch moveMode {
+	case horizontal:
+		position.X += int16(param)
+	case vertical:
+		position.Y += int16(param)
+	}
+
+	if err = h.setCursorPosition(position, h.getCursorWindow(info)); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) moveCursorLine(param int) error {
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	position := info.CursorPosition
+	position.X = 0
+	position.Y += int16(param)
+
+	if err = h.setCursorPosition(position, h.getCursorWindow(info)); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) moveCursorColumn(param int) error {
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	position := info.CursorPosition
+	position.X = int16(param) - 1
+
+	if err = h.setCursorPosition(position, h.getCursorWindow(info)); err != nil {
+		return err
+	}
+
+	return nil
+}
@@ -0,0 +1,84 @@
+// +build windows
+
+package winterm
+
+import "github.com/Azure/go-ansiterm"
+
+func (h *windowsAnsiEventHandler) clearRange(attributes uint16, fromCoord COORD, toCoord COORD) error {
+	// Ignore an invalid (negative area) request
+	if toCoord.Y < fromCoord.Y {
+		return nil
+	}
+
+	var err error
+
+	var coordStart = COORD{}
+	var coordEnd = COORD{}
+
+	xCurrent, yCurrent := fromCoord.X, fromCoord.Y
+	xEnd, yEnd := toCoord.X, toCoord.Y
+
+	// Clear any partial initial line
+	if xCurrent > 0 {
+		coordStart.X, coordStart.Y = xCurrent, yCurrent
+		coordEnd.X, coordEnd.Y = xEnd, yCurrent
+
+		err = h.clearRect(attributes, coordStart, coordEnd)
+		if err != nil {
+			return err
+		}
+
+		xCurrent = 0
+		yCurrent += 1
+	}
+
+	// Clear intervening rectangular section
+	if yCurrent < yEnd {
+		coordStart.X, coordStart.Y = xCurrent, yCurrent
+		coordEnd.X, coordEnd.Y = xEnd, yEnd-1
+
+		err = h.clearRect(attributes, coordStart, coordEnd)
+		if err != nil {
+			return err
+		}
+
+		xCurrent = 0
+		yCurrent = yEnd
+	}
+
+	// Clear remaining partial ending line
+	coordStart.X, coordStart.Y = xCurrent, yCurrent
+	coordEnd.X, coordEnd.Y = xEnd, yEnd
+
+	err = h.clearRect(attributes, coordStart, coordEnd)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) clearRect(attributes uint16, fromCoord COORD, toCoord COORD) error {
+	region := SMALL_RECT{Top: fromCoord.Y, Left: fromCoord.X, Bottom: toCoord.Y, Right: toCoord.X}
+	width := toCoord.X - fromCoord.X + 1
+	height := toCoord.Y - fromCoord.Y + 1
+	size := uint32(width) * uint32(height)
+
+	if size <= 0 {
+		return nil
+	}
+
+	buffer := make([]CHAR_INFO, size)
+
+	char := CHAR_INFO{ansiterm.FILL_CHARACTER, attributes}
+	for i := 0; i < int(size); i++ {
+		buffer[i] = char
+	}
+
+	err := WriteConsoleOutput(h.fd, buffer, COORD{X: width, Y: height}, COORD{X: 0, Y: 0}, &region)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
@@ -0,0 +1,118 @@
+// +build windows
+
+package winterm
+
+// effectiveSr gets the current effective scroll region in buffer coordinates
+func (h *windowsAnsiEventHandler) effectiveSr(window SMALL_RECT) scrollRegion {
+	top := addInRange(window.Top, h.sr.top, window.Top, window.Bottom)
+	bottom := addInRange(window.Top, h.sr.bottom, window.Top, window.Bottom)
+	if top >= bottom {
+		top = window.Top
+		bottom = window.Bottom
+	}
+	return scrollRegion{top: top, bottom: bottom}
+}
+
+func (h *windowsAnsiEventHandler) scrollUp(param int) error {
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	sr := h.effectiveSr(info.Window)
+	return h.scroll(param, sr, info)
+}
+
+func (h *windowsAnsiEventHandler) scrollDown(param int) error {
+	return h.scrollUp(-param)
+}
+
+func (h *windowsAnsiEventHandler) deleteLines(param int) error {
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	start := info.CursorPosition.Y
+	sr := h.effectiveSr(info.Window)
+	// Lines cannot be inserted or deleted outside the scrolling region.
+	if start >= sr.top && start <= sr.bottom {
+		sr.top = start
+		return h.scroll(param, sr, info)
+	} else {
+		return nil
+	}
+}
+
+func (h *windowsAnsiEventHandler) insertLines(param int) error {
+	return h.deleteLines(-param)
+}
+
+// scroll scrolls the provided scroll region by param lines. The scroll region is in buffer coordinates.
+func (h *windowsAnsiEventHandler) scroll(param int, sr scrollRegion, info *CONSOLE_SCREEN_BUFFER_INFO) error {
+	h.logf("scroll: scrollTop: %d, scrollBottom: %d", sr.top, sr.bottom)
+	h.logf("scroll: windowTop: %d, windowBottom: %d", info.Window.Top, info.Window.Bottom)
+
+	// Copy from and clip to the scroll region (full buffer width)
+	scrollRect := SMALL_RECT{
+		Top:    sr.top,
+		Bottom: sr.bottom,
+		Left:   0,
+		Right:  info.Size.X - 1,
+	}
+
+	// Origin to which area should be copied
+	destOrigin := COORD{
+		X: 0,
+		Y: sr.top - int16(param),
+	}
+
+	char := CHAR_INFO{
+		UnicodeChar: ' ',
+		Attributes:  h.attributes,
+	}
+
+	if err := ScrollConsoleScreenBuffer(h.fd, scrollRect, scrollRect, destOrigin, char); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) deleteCharacters(param int) error {
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+	return h.scrollLine(param, info.CursorPosition, info)
+}
+
+func (h *windowsAnsiEventHandler) insertCharacters(param int) error {
+	return h.deleteCharacters(-param)
+}
+
+// scrollLine scrolls a line horizontally starting at the provided position by a number of columns.
+func (h *windowsAnsiEventHandler) scrollLine(columns int, position COORD, info *CONSOLE_SCREEN_BUFFER_INFO) error {
+	// Copy from and clip to the scroll region (full buffer width)
+	scrollRect := SMALL_RECT{
+		Top:    position.Y,
+		Bottom: position.Y,
+		Left:   position.X,
+		Right:  info.Size.X - 1,
+	}
+
+	// Origin to which area should be copied
+	destOrigin := COORD{
+		X: position.X - int16(columns),
+		Y: position.Y,
+	}
+
+	char := CHAR_INFO{
+		UnicodeChar: ' ',
+		Attributes:  h.attributes,
+	}
+
+	if err := ScrollConsoleScreenBuffer(h.fd, scrollRect, scrollRect, destOrigin, char); err != nil {
+		return err
+	}
+	return nil
+}
@@ -0,0 +1,9 @@
+// +build windows
+
+package winterm
+
+// AddInRange increments a value by the passed quantity while ensuring the values
+// always remain within the supplied min / max range.
+func addInRange(n int16, increment int16, min int16, max int16) int16 {
+	return ensureInRange(n+increment, min, max)
+}
@@ -0,0 +1,743 @@
+// +build windows
+
+package winterm
+
+import (
+	"bytes"
+	"log"
+	"os"
+	"strconv"
+
+	"github.com/Azure/go-ansiterm"
+)
+
+type windowsAnsiEventHandler struct {
+	fd             uintptr
+	file           *os.File
+	infoReset      *CONSOLE_SCREEN_BUFFER_INFO
+	sr             scrollRegion
+	buffer         bytes.Buffer
+	attributes     uint16
+	inverted       bool
+	wrapNext       bool
+	drewMarginByte bool
+	originMode     bool
+	marginByte     byte
+	curInfo        *CONSOLE_SCREEN_BUFFER_INFO
+	curPos         COORD
+	logf           func(string, ...interface{})
+}
+
+type Option func(*windowsAnsiEventHandler)
+
+func WithLogf(f func(string, ...interface{})) Option {
+	return func(w *windowsAnsiEventHandler) {
+		w.logf = f
+	}
+}
+
+func CreateWinEventHandler(fd uintptr, file *os.File, opts ...Option) ansiterm.AnsiEventHandler {
+	infoReset, err := GetConsoleScreenBufferInfo(fd)
+	if err != nil {
+		return nil
+	}
+
+	h := &windowsAnsiEventHandler{
+		fd:         fd,
+		file:       file,
+		infoReset:  infoReset,
+		attributes: infoReset.Attributes,
+	}
+	for _, o := range opts {
+		o(h)
+	}
+
+	if isDebugEnv := os.Getenv(ansiterm.LogEnv); isDebugEnv == "1" {
+		logFile, _ := os.Create("winEventHandler.log")
+		logger := log.New(logFile, "", log.LstdFlags)
+		if h.logf != nil {
+			l := h.logf
+			h.logf = func(s string, v ...interface{}) {
+				l(s, v...)
+				logger.Printf(s, v...)
+			}
+		} else {
+			h.logf = logger.Printf
+		}
+	}
+
+	if h.logf == nil {
+		h.logf = func(string, ...interface{}) {}
+	}
+
+	return h
+}
+
+type scrollRegion struct {
+	top    int16
+	bottom int16
+}
+
+// simulateLF simulates a LF or CR+LF by scrolling if necessary to handle the
+// current cursor position and scroll region settings, in which case it returns
+// true. If no special handling is necessary, then it does nothing and returns
+// false.
+//
+// In the false case, the caller should ensure that a carriage return
+// and line feed are inserted or that the text is otherwise wrapped.
+func (h *windowsAnsiEventHandler) simulateLF(includeCR bool) (bool, error) {
+	if h.wrapNext {
+		if err := h.Flush(); err != nil {
+			return false, err
+		}
+		h.clearWrap()
+	}
+	pos, info, err := h.getCurrentInfo()
+	if err != nil {
+		return false, err
+	}
+	sr := h.effectiveSr(info.Window)
+	if pos.Y == sr.bottom {
+		// Scrolling is necessary. Let Windows automatically scroll if the scrolling region
+		// is the full window.
+		if sr.top == info.Window.Top && sr.bottom == info.Window.Bottom {
+			if includeCR {
+				pos.X = 0
+				h.updatePos(pos)
+			}
+			return false, nil
+		}
+
+		// A custom scroll region is active. Scroll the window manually to simulate
+		// the LF.
+		if err := h.Flush(); err != nil {
+			return false, err
+		}
+		h.logf("Simulating LF inside scroll region")
+		if err := h.scrollUp(1); err != nil {
+			return false, err
+		}
+		if includeCR {
+			pos.X = 0
+			if err := SetConsoleCursorPosition(h.fd, pos); err != nil {
+				return false, err
+			}
+		}
+		return true, nil
+
+	} else if pos.Y < info.Window.Bottom {
+		// Let Windows handle the LF.
+		pos.Y++
+		if includeCR {
+			pos.X = 0
+		}
+		h.updatePos(pos)
+		return false, nil
+	} else {
+		// The cursor is at the bottom of the screen but outside the scroll
+		// region. Skip the LF.
+		h.logf("Simulating LF outside scroll region")
+		if includeCR {
+			if err := h.Flush(); err != nil {
+				return false, err
+			}
+			pos.X = 0
+			if err := SetConsoleCursorPosition(h.fd, pos); err != nil {
+				return false, err
+			}
+		}
+		return true, nil
+	}
+}
+
+// executeLF executes a LF without a CR.
+func (h *windowsAnsiEventHandler) executeLF() error {
+	handled, err := h.simulateLF(false)
+	if err != nil {
+		return err
+	}
+	if !handled {
+		// Windows LF will reset the cursor column position. Write the LF
+		// and restore the cursor position.
+		pos, _, err := h.getCurrentInfo()
+		if err != nil {
+			return err
+		}
+		h.buffer.WriteByte(ansiterm.ANSI_LINE_FEED)
+		if pos.X != 0 {
+			if err := h.Flush(); err != nil {
+				return err
+			}
+			h.logf("Resetting cursor position for LF without CR")
+			if err := SetConsoleCursorPosition(h.fd, pos); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) Print(b byte) error {
+	if h.wrapNext {
+		h.buffer.WriteByte(h.marginByte)
+		h.clearWrap()
+		if _, err := h.simulateLF(true); err != nil {
+			return err
+		}
+	}
+	pos, info, err := h.getCurrentInfo()
+	if err != nil {
+		return err
+	}
+	if pos.X == info.Size.X-1 {
+		h.wrapNext = true
+		h.marginByte = b
+	} else {
+		pos.X++
+		h.updatePos(pos)
+		h.buffer.WriteByte(b)
+	}
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) Execute(b byte) error {
+	switch b {
+	case ansiterm.ANSI_TAB:
+		h.logf("Execute(TAB)")
+		// Move to the next tab stop, but preserve auto-wrap if already set.
+		if !h.wrapNext {
+			pos, info, err := h.getCurrentInfo()
+			if err != nil {
+				return err
+			}
+			pos.X = (pos.X + 8) - pos.X%8
+			if pos.X >= info.Size.X {
+				pos.X = info.Size.X - 1
+			}
+			if err := h.Flush(); err != nil {
+				return err
+			}
+			if err := SetConsoleCursorPosition(h.fd, pos); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	case ansiterm.ANSI_BEL:
+		h.buffer.WriteByte(ansiterm.ANSI_BEL)
+		return nil
+
+	case ansiterm.ANSI_BACKSPACE:
+		if h.wrapNext {
+			if err := h.Flush(); err != nil {
+				return err
+			}
+			h.clearWrap()
+		}
+		pos, _, err := h.getCurrentInfo()
+		if err != nil {
+			return err
+		}
+		if pos.X > 0 {
+			pos.X--
+			h.updatePos(pos)
+			h.buffer.WriteByte(ansiterm.ANSI_BACKSPACE)
+		}
+		return nil
+
+	case ansiterm.ANSI_VERTICAL_TAB, ansiterm.ANSI_FORM_FEED:
+		// Treat as true LF.
+		return h.executeLF()
+
+	case ansiterm.ANSI_LINE_FEED:
+		// Simulate a CR and LF for now since there is no way in go-ansiterm
+		// to tell if the LF should include CR (and more things break when it's
+		// missing than when it's incorrectly added).
+		handled, err := h.simulateLF(true)
+		if handled || err != nil {
+			return err
+		}
+		return h.buffer.WriteByte(ansiterm.ANSI_LINE_FEED)
+
+	case ansiterm.ANSI_CARRIAGE_RETURN:
+		if h.wrapNext {
+			if err := h.Flush(); err != nil {
+				return err
+			}
+			h.clearWrap()
+		}
+		pos, _, err := h.getCurrentInfo()
+		if err != nil {
+			return err
+		}
+		if pos.X != 0 {
+			pos.X = 0
+			h.updatePos(pos)
+			h.buffer.WriteByte(ansiterm.ANSI_CARRIAGE_RETURN)
+		}
+		return nil
+
+	default:
+		return nil
+	}
+}
+
+func (h *windowsAnsiEventHandler) CUU(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CUU: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorVertical(-param)
+}
+
+func (h *windowsAnsiEventHandler) CUD(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CUD: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorVertical(param)
+}
+
+func (h *windowsAnsiEventHandler) CUF(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CUF: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorHorizontal(param)
+}
+
+func (h *windowsAnsiEventHandler) CUB(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CUB: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorHorizontal(-param)
+}
+
+func (h *windowsAnsiEventHandler) CNL(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CNL: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorLine(param)
+}
+
+func (h *windowsAnsiEventHandler) CPL(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CPL: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorLine(-param)
+}
+
+func (h *windowsAnsiEventHandler) CHA(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CHA: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.moveCursorColumn(param)
+}
+
+func (h *windowsAnsiEventHandler) VPA(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("VPA: [[%d]]", param)
+	h.clearWrap()
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+	window := h.getCursorWindow(info)
+	position := info.CursorPosition
+	position.Y = window.Top + int16(param) - 1
+	return h.setCursorPosition(position, window)
+}
+
+func (h *windowsAnsiEventHandler) CUP(row int, col int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("CUP: [[%d %d]]", row, col)
+	h.clearWrap()
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	window := h.getCursorWindow(info)
+	position := COORD{window.Left + int16(col) - 1, window.Top + int16(row) - 1}
+	return h.setCursorPosition(position, window)
+}
+
+func (h *windowsAnsiEventHandler) HVP(row int, col int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("HVP: [[%d %d]]", row, col)
+	h.clearWrap()
+	return h.CUP(row, col)
+}
+
+func (h *windowsAnsiEventHandler) DECTCEM(visible bool) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("DECTCEM: [%v]", []string{strconv.FormatBool(visible)})
+	h.clearWrap()
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) DECOM(enable bool) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("DECOM: [%v]", []string{strconv.FormatBool(enable)})
+	h.clearWrap()
+	h.originMode = enable
+	return h.CUP(1, 1)
+}
+
+func (h *windowsAnsiEventHandler) DECCOLM(use132 bool) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("DECCOLM: [%v]", []string{strconv.FormatBool(use132)})
+	h.clearWrap()
+	if err := h.ED(2); err != nil {
+		return err
+	}
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+	targetWidth := int16(80)
+	if use132 {
+		targetWidth = 132
+	}
+	if info.Size.X < targetWidth {
+		if err := SetConsoleScreenBufferSize(h.fd, COORD{targetWidth, info.Size.Y}); err != nil {
+			h.logf("set buffer failed: %v", err)
+			return err
+		}
+	}
+	window := info.Window
+	window.Left = 0
+	window.Right = targetWidth - 1
+	if err := SetConsoleWindowInfo(h.fd, true, window); err != nil {
+		h.logf("set window failed: %v", err)
+		return err
+	}
+	if info.Size.X > targetWidth {
+		if err := SetConsoleScreenBufferSize(h.fd, COORD{targetWidth, info.Size.Y}); err != nil {
+			h.logf("set buffer failed: %v", err)
+			return err
+		}
+	}
+	return SetConsoleCursorPosition(h.fd, COORD{0, 0})
+}
+
+func (h *windowsAnsiEventHandler) ED(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("ED: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+
+	// [J  -- Erases from the cursor to the end of the screen, including the cursor position.
+	// [1J -- Erases from the beginning of the screen to the cursor, including the cursor position.
+	// [2J -- Erases the complete display. The cursor does not move.
+	// Notes:
+	// -- Clearing the entire buffer, versus just the Window, works best for Windows Consoles
+
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	var start COORD
+	var end COORD
+
+	switch param {
+	case 0:
+		start = info.CursorPosition
+		end = COORD{info.Size.X - 1, info.Size.Y - 1}
+
+	case 1:
+		start = COORD{0, 0}
+		end = info.CursorPosition
+
+	case 2:
+		start = COORD{0, 0}
+		end = COORD{info.Size.X - 1, info.Size.Y - 1}
+	}
+
+	err = h.clearRange(h.attributes, start, end)
+	if err != nil {
+		return err
+	}
+
+	// If the whole buffer was cleared, move the window to the top while preserving
+	// the window-relative cursor position.
+	if param == 2 {
+		pos := info.CursorPosition
+		window := info.Window
+		pos.Y -= window.Top
+		window.Bottom -= window.Top
+		window.Top = 0
+		if err := SetConsoleCursorPosition(h.fd, pos); err != nil {
+			return err
+		}
+		if err := SetConsoleWindowInfo(h.fd, true, window); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) EL(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("EL: [%v]", strconv.Itoa(param))
+	h.clearWrap()
+
+	// [K  -- Erases from the cursor to the end of the line, including the cursor position.
+	// [1K -- Erases from the beginning of the line to the cursor, including the cursor position.
+	// [2K -- Erases the complete line.
+
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	var start COORD
+	var end COORD
+
+	switch param {
+	case 0:
+		start = info.CursorPosition
+		end = COORD{info.Size.X, info.CursorPosition.Y}
+
+	case 1:
+		start = COORD{0, info.CursorPosition.Y}
+		end = info.CursorPosition
+
+	case 2:
+		start = COORD{0, info.CursorPosition.Y}
+		end = COORD{info.Size.X, info.CursorPosition.Y}
+	}
+
+	err = h.clearRange(h.attributes, start, end)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) IL(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("IL: [%v]", strconv.Itoa(param))
+	h.clearWrap()
+	return h.insertLines(param)
+}
+
+func (h *windowsAnsiEventHandler) DL(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("DL: [%v]", strconv.Itoa(param))
+	h.clearWrap()
+	return h.deleteLines(param)
+}
+
+func (h *windowsAnsiEventHandler) ICH(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("ICH: [%v]", strconv.Itoa(param))
+	h.clearWrap()
+	return h.insertCharacters(param)
+}
+
+func (h *windowsAnsiEventHandler) DCH(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("DCH: [%v]", strconv.Itoa(param))
+	h.clearWrap()
+	return h.deleteCharacters(param)
+}
+
+func (h *windowsAnsiEventHandler) SGR(params []int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	strings := []string{}
+	for _, v := range params {
+		strings = append(strings, strconv.Itoa(v))
+	}
+
+	h.logf("SGR: [%v]", strings)
+
+	if len(params) <= 0 {
+		h.attributes = h.infoReset.Attributes
+		h.inverted = false
+	} else {
+		for _, attr := range params {
+
+			if attr == ansiterm.ANSI_SGR_RESET {
+				h.attributes = h.infoReset.Attributes
+				h.inverted = false
+				continue
+			}
+
+			h.attributes, h.inverted = collectAnsiIntoWindowsAttributes(h.attributes, h.inverted, h.infoReset.Attributes, int16(attr))
+		}
+	}
+
+	attributes := h.attributes
+	if h.inverted {
+		attributes = invertAttributes(attributes)
+	}
+	err := SetConsoleTextAttribute(h.fd, attributes)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) SU(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("SU: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.scrollUp(param)
+}
+
+func (h *windowsAnsiEventHandler) SD(param int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("SD: [%v]", []string{strconv.Itoa(param)})
+	h.clearWrap()
+	return h.scrollDown(param)
+}
+
+func (h *windowsAnsiEventHandler) DA(params []string) error {
+	h.logf("DA: [%v]", params)
+	// DA cannot be implemented because it must send data on the VT100 input stream,
+	// which is not available to go-ansiterm.
+	return nil
+}
+
+func (h *windowsAnsiEventHandler) DECSTBM(top int, bottom int) error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("DECSTBM: [%d, %d]", top, bottom)
+
+	// Windows is 0 indexed, Linux is 1 indexed
+	h.sr.top = int16(top - 1)
+	h.sr.bottom = int16(bottom - 1)
+
+	// This command also moves the cursor to the origin.
+	h.clearWrap()
+	return h.CUP(1, 1)
+}
+
+func (h *windowsAnsiEventHandler) RI() error {
+	if err := h.Flush(); err != nil {
+		return err
+	}
+	h.logf("RI: []")
+	h.clearWrap()
+
+	info, err := GetConsoleScreenBufferInfo(h.fd)
+	if err != nil {
+		return err
+	}
+
+	sr := h.effectiveSr(info.Window)
+	if info.CursorPosition.Y == sr.top {
+		return h.scrollDown(1)
+	}
+
+	return h.moveCursorVertical(-1)
+}
+
+func (h *windowsAnsiEventHandler) IND() error {
+	h.logf("IND: []")
+	return h.executeLF()
+}
+
+func (h *windowsAnsiEventHandler) Flush() error {
+	h.curInfo = nil
+	if h.buffer.Len() > 0 {
+		h.logf("Flush: [%s]", h.buffer.Bytes())
+		if _, err := h.buffer.WriteTo(h.file); err != nil {
+			return err
+		}
+	}
+
+	if h.wrapNext && !h.drewMarginByte {
+		h.logf("Flush: drawing margin byte '%c'", h.marginByte)
+
+		info, err := GetConsoleScreenBufferInfo(h.fd)
+		if err != nil {
+			return err
+		}
+
+		charInfo := []CHAR_INFO{{UnicodeChar: uint16(h.marginByte), Attributes: info.Attributes}}
+		size := COORD{1, 1}
+		position := COORD{0, 0}
+		region := SMALL_RECT{Left: info.CursorPosition.X, Top: info.CursorPosition.Y, Right: info.CursorPosition.X, Bottom: info.CursorPosition.Y}
+		if err := WriteConsoleOutput(h.fd, charInfo, size, position, &region); err != nil {
+			return err
+		}
+		h.drewMarginByte = true
+	}
+	return nil
+}
+
+// cacheConsoleInfo ensures that the current console screen information has been queried
+// since the last call to Flush(). It must be called before accessing h.curInfo or h.curPos.
+func (h *windowsAnsiEventHandler) getCurrentInfo() (COORD, *CONSOLE_SCREEN_BUFFER_INFO, error) {
+	if h.curInfo == nil {
+		info, err := GetConsoleScreenBufferInfo(h.fd)
+		if err != nil {
+			return COORD{}, nil, err
+		}
+		h.curInfo = info
+		h.curPos = info.CursorPosition
+	}
+	return h.curPos, h.curInfo, nil
+}
+
+func (h *windowsAnsiEventHandler) updatePos(pos COORD) {
+	if h.curInfo == nil {
+		panic("failed to call getCurrentInfo before calling updatePos")
+	}
+	h.curPos = pos
+}
+
+// clearWrap clears the state where the cursor is in the margin
+// waiting for the next character before wrapping the line. This must
+// be done before most operations that act on the cursor.
+func (h *windowsAnsiEventHandler) clearWrap() {
+	h.wrapNext = false
+	h.drewMarginByte = false
+}
@@ -0,0 +1,2 @@
+.vscode
+*.exe
@@ -0,0 +1,39 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+version: "2"
+linters:
+  enable:
+    - bodyclose
+    - godox
+    - nakedret
+    - predeclared
+    - unconvert
+  exclusions:
+    generated: lax
+    presets:
+      - comments
+      - common-false-positives
+      - legacy
+      - std-error-handling
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
+      - internal/md4
+    rules:
+      - path: negotiate_flags.go
+        linters:
+          - unused
+      - path: negotiator.go
+        text: "QF1001:"
+formatters:
+  enable:
+    - gofumpt
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
+      - internal/md4
@@ -0,0 +1,107 @@
+# E2E NTLM Tests
+
+This directory contains end-to-end tests for the go-ntlmssp library that test against real NTLM servers.
+
+## Running E2E Tests Locally
+
+### Prerequisites
+
+- Windows machine with IIS capabilities
+- Go 1.20 or later
+- Administrator privileges (for IIS setup)
+
+### Setup
+
+1. **Enable IIS with Windows Authentication:**
+   ```powershell
+   # Run as Administrator
+   Enable-WindowsOptionalFeature -Online -FeatureName IIS-WebServerRole -All
+   Enable-WindowsOptionalFeature -Online -FeatureName IIS-WindowsAuthentication -All
+   ```
+
+2. **Create test site:**
+   ```powershell
+   Import-Module WebAdministration
+   New-Website -Name "ntlmtest" -Port 8080 -PhysicalPath "C:\inetpub\wwwroot"
+   Set-WebConfigurationProperty -Filter "/system.webServer/security/authentication/anonymousAuthentication" -Name enabled -Value false -PSPath "IIS:\Sites\ntlmtest"
+   Set-WebConfigurationProperty -Filter "/system.webServer/security/authentication/windowsAuthentication" -Name enabled -Value true -PSPath "IIS:\Sites\ntlmtest"
+   ```
+
+3. **Set environment variables:**
+   ```powershell
+   $env:NTLM_TEST_URL = "http://localhost:8080/"
+   $env:NTLM_TEST_USER = "your_username"
+   $env:NTLM_TEST_PASSWORD = "your_password" 
+   $env:NTLM_TEST_DOMAIN = "your_domain"  # Optional
+   ```
+   
+   > **Note**: The setup script automatically generates a random secure password if none is provided. For security, avoid hardcoded passwords in scripts or CI environments.
+
+4. **Run tests:**
+   ```bash
+   go test -v -tags=e2e ./e2e -run TestNTLM_E2E
+   ```
+
+## GitHub Actions
+
+The E2E tests run automatically in GitHub Actions on Windows runners. The workflow:
+
+1. Sets up a clean Windows Server environment
+2. Generates a random secure password for the test user
+3. Creates a test user account with the random password
+4. Configures IIS with Windows Authentication
+5. Runs the E2E tests against the real NTLM server
+5. Cleans up resources
+
+## Test Coverage
+
+The E2E tests cover:
+
+- ✅ Basic NTLM authentication flow
+- ✅ UPN format usernames (`user@domain.com`)
+- ✅ SAM format usernames (`DOMAIN\user`) 
+- ✅ Authentication failure scenarios
+- ✅ Server accessibility checks
+- ✅ Context cancellation handling
+- ✅ Direct ProcessChallenge function testing
+
+## Environment Variables
+
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `NTLM_TEST_URL` | URL of NTLM-enabled server | `http://localhost:8080/` |
+| `NTLM_TEST_USER` | Username for authentication | `$USERNAME` (Windows) |
+| `NTLM_TEST_PASSWORD` | Password for authentication | Required |
+| `NTLM_TEST_DOMAIN` | Domain for authentication | `$USERDOMAIN` (Windows) |
+
+## Troubleshooting
+
+### Common Issues
+
+1. **"No username available"** - Set `NTLM_TEST_USER` environment variable
+2. **"No password available"** - Set `NTLM_TEST_PASSWORD` environment variable  
+3. **Connection refused** - Ensure IIS is running and accessible on the specified port
+4. **401 Unauthorized** - Check that Windows Authentication is enabled and working
+
+### IIS Debugging
+
+Check IIS status:
+```powershell
+Get-Website
+Get-WebApplication
+Get-WebConfigurationProperty -Filter "/system.webServer/security/authentication/windowsAuthentication" -Name enabled -PSPath "IIS:\Sites\Default Web Site"
+```
+
+View IIS logs:
+```powershell
+Get-Content "C:\inetpub\logs\LogFiles\W3SVC1\*.log" | Select-Object -Last 50
+```
+
+## Security Note
+
+These tests use real authentication credentials. In CI/CD:
+- Test credentials are generated dynamically per job
+- Credentials are cleaned up after each test run
+- No persistent credentials are stored
+
+For local development, use test accounts or ensure credentials are not committed to version control.
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2016 Microsoft
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
@@ -0,0 +1,39 @@
+# go-ntlmssp
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/Azure/go-ntlmssp.svg)](https://pkg.go.dev/github.com/Azure/go-ntlmssp) [![Test](https://github.com/Azure/go-ntlmssp/actions/workflows/test.yml/badge.svg)](https://github.com/Azure/go-ntlmssp/actions/workflows/test.yml)
+
+Go package that provides NTLM/Negotiate authentication over HTTP
+
+* NTLM protocol details from https://msdn.microsoft.com/en-us/library/cc236621.aspx
+* NTLM over HTTP details from https://datatracker.ietf.org/doc/html/rfc4559
+* Implementation hints from http://davenport.sourceforge.net/ntlm.html
+
+This package only implements authentication, no key exchange or encryption. It
+only supports Unicode (UTF16LE) encoding of protocol strings, no OEM encoding.
+This package implements NTLMv2.
+
+# Installation
+
+To install the package, use `go get`:
+
+```bash
+go get github.com/Azure/go-ntlmssp
+```
+
+# Usage
+
+```go
+url, user, password := "http://www.example.com/secrets", "robpike", "pw123"
+client := &http.Client{
+  Transport: ntlmssp.Negotiator{
+    RoundTripper: &http.Transport{},
+  },
+}
+
+req, _ := http.NewRequest("GET", url, nil)
+req.SetBasicAuth(user, password)
+res, _ := client.Do(req)
+```
+
+-----
+This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
@@ -0,0 +1,41 @@
+<!-- BEGIN MICROSOFT SECURITY.MD V0.0.8 BLOCK -->
+
+## Security
+
+Microsoft takes the security of our software products and services seriously, which includes all source code repositories managed through our GitHub organizations, which include [Microsoft](https://github.com/microsoft), [Azure](https://github.com/Azure), [DotNet](https://github.com/dotnet), [AspNet](https://github.com/aspnet), [Xamarin](https://github.com/xamarin), and [our GitHub organizations](https://opensource.microsoft.com/).
+
+If you believe you have found a security vulnerability in any Microsoft-owned repository that meets [Microsoft's definition of a security vulnerability](https://aka.ms/opensource/security/definition), please report it to us as described below.
+
+## Reporting Security Issues
+
+**Please do not report security vulnerabilities through public GitHub issues.**
+
+Instead, please report them to the Microsoft Security Response Center (MSRC) at [https://msrc.microsoft.com/create-report](https://aka.ms/opensource/security/create-report).
+
+If you prefer to submit without logging in, send email to [secure@microsoft.com](mailto:secure@microsoft.com).  If possible, encrypt your message with our PGP key; please download it from the [Microsoft Security Response Center PGP Key page](https://aka.ms/opensource/security/pgpkey).
+
+You should receive a response within 24 hours. If for some reason you do not, please follow up via email to ensure we received your original message. Additional information can be found at [microsoft.com/msrc](https://aka.ms/opensource/security/msrc). 
+
+Please include the requested information listed below (as much as you can provide) to help us better understand the nature and scope of the possible issue:
+
+  * Type of issue (e.g. buffer overflow, SQL injection, cross-site scripting, etc.)
+  * Full paths of source file(s) related to the manifestation of the issue
+  * The location of the affected source code (tag/branch/commit or direct URL)
+  * Any special configuration required to reproduce the issue
+  * Step-by-step instructions to reproduce the issue
+  * Proof-of-concept or exploit code (if possible)
+  * Impact of the issue, including how an attacker might exploit the issue
+
+This information will help us triage your report more quickly.
+
+If you are reporting for a bug bounty, more complete reports can contribute to a higher bounty award. Please visit our [Microsoft Bug Bounty Program](https://aka.ms/opensource/security/bounty) page for more details about our active programs.
+
+## Preferred Languages
+
+We prefer all communications to be in English.
+
+## Policy
+
+Microsoft follows the principle of [Coordinated Vulnerability Disclosure](https://aka.ms/opensource/security/cvd).
+
+<!-- END MICROSOFT SECURITY.MD BLOCK -->
@@ -0,0 +1,194 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"strings"
+	"time"
+)
+
+type authenicateMessage struct {
+	LmChallengeResponse []byte
+	NtChallengeResponse []byte
+
+	DomainName  string
+	UserName    string
+	Workstation string
+
+	// only set if negotiateFlag_NTLMSSP_NEGOTIATE_KEY_EXCH
+	EncryptedRandomSessionKey []byte
+
+	NegotiateFlags negotiateFlags
+
+	MIC []byte
+}
+
+type authenticateMessageFields struct {
+	messageHeader
+	LmChallengeResponse varField
+	NtChallengeResponse varField
+	DomainName          varField
+	UserName            varField
+	Workstation         varField
+	_                   [8]byte
+	NegotiateFlags      negotiateFlags
+}
+
+func (m *authenicateMessage) MarshalBinary() ([]byte, error) {
+	if !m.NegotiateFlags.Has(negotiateFlagNTLMSSPNEGOTIATEUNICODE) {
+		return nil, errors.New("only unicode is supported")
+	}
+
+	domain, user := toUnicode(m.DomainName), toUnicode(m.UserName)
+	workstation := toUnicode(m.Workstation)
+
+	ptr := binary.Size(&authenticateMessageFields{})
+	f := authenticateMessageFields{
+		messageHeader:       newMessageHeader(3),
+		NegotiateFlags:      m.NegotiateFlags,
+		LmChallengeResponse: newVarField(&ptr, len(m.LmChallengeResponse)),
+		NtChallengeResponse: newVarField(&ptr, len(m.NtChallengeResponse)),
+		DomainName:          newVarField(&ptr, len(domain)),
+		UserName:            newVarField(&ptr, len(user)),
+		Workstation:         newVarField(&ptr, len(workstation)),
+	}
+
+	f.NegotiateFlags.Unset(negotiateFlagNTLMSSPNEGOTIATEVERSION)
+
+	b := bytes.Buffer{}
+	if err := binary.Write(&b, binary.LittleEndian, &f); err != nil {
+		return nil, err
+	}
+	if err := binary.Write(&b, binary.LittleEndian, &m.LmChallengeResponse); err != nil {
+		return nil, err
+	}
+	if err := binary.Write(&b, binary.LittleEndian, &m.NtChallengeResponse); err != nil {
+		return nil, err
+	}
+	if err := binary.Write(&b, binary.LittleEndian, &domain); err != nil {
+		return nil, err
+	}
+	if err := binary.Write(&b, binary.LittleEndian, &user); err != nil {
+		return nil, err
+	}
+	if err := binary.Write(&b, binary.LittleEndian, &workstation); err != nil {
+		return nil, err
+	}
+
+	return b.Bytes(), nil
+}
+
+func splitNameForAuth(username string) (user, domain string) {
+	if strings.Contains(username, "\\") {
+		ucomponents := strings.SplitN(username, "\\", 2)
+		domain = ucomponents[0]
+		user = ucomponents[1]
+	} else if strings.Contains(username, "@") {
+		user = username
+	} else {
+		user = username
+	}
+	return user, domain
+}
+
+// AuthenticateMessageOptions contains optional parameters for the Authenticate message.
+type AuthenticateMessageOptions struct {
+	WorkstationName string
+
+	// PasswordHashed indicates whether the provided password is already hashed.
+	// If true, the password is expected to be in hexadecimal format.
+	PasswordHashed bool
+}
+
+// NewAuthenticateMessage creates a new AUTHENTICATE message in response to the CHALLENGE message that was received from the server.
+// The options parameter allows specifying additional settings for the message, it can be nil to use defaults.
+func NewAuthenticateMessage(challenge []byte, username, password string, options *AuthenticateMessageOptions) ([]byte, error) {
+	if username == "" && password == "" {
+		return nil, errors.New("anonymous authentication not supported")
+	}
+
+	var cm challengeMessage
+	if err := cm.UnmarshalBinary(challenge); err != nil {
+		return nil, err
+	}
+
+	if cm.NegotiateFlags.Has(negotiateFlagNTLMSSPNEGOTIATELMKEY) {
+		return nil, errors.New("only NTLM v2 is supported, but server requested v1 (NTLMSSP_NEGOTIATE_LM_KEY)")
+	}
+	if cm.NegotiateFlags.Has(negotiateFlagNTLMSSPNEGOTIATEKEYEXCH) {
+		return nil, errors.New("key exchange requested but not supported (NTLMSSP_NEGOTIATE_KEY_EXCH)")
+	}
+
+	am := authenicateMessage{
+		NegotiateFlags: cm.NegotiateFlags,
+	}
+	am.UserName, am.DomainName = splitNameForAuth(username)
+	if options != nil {
+		am.Workstation = options.WorkstationName
+	}
+
+	timestamp := cm.TargetInfo[avIDMsvAvTimestamp]
+	if timestamp == nil { // no time sent, take current time
+		ft := uint64(time.Now().UnixNano()) / 100
+		ft += 116444736000000000 // add time between unix & windows offset
+		timestamp = make([]byte, 8)
+		binary.LittleEndian.PutUint64(timestamp, ft)
+	}
+
+	clientChallenge := make([]byte, 8)
+	if _, err := rand.Reader.Read(clientChallenge); err != nil {
+		return nil, err
+	}
+
+	var ntlmV2Hash []byte
+	if options != nil && options.PasswordHashed {
+		hashParts := strings.Split(password, ":")
+		if len(hashParts) > 1 {
+			password = hashParts[1]
+		}
+		hashBytes, err := hex.DecodeString(password)
+		if err != nil {
+			return nil, err
+		}
+		ntlmV2Hash = getNtlmV2Hashed(hashBytes, am.UserName, am.DomainName)
+	} else {
+		ntlmV2Hash = getNtlmV2Hash(password, am.UserName, am.DomainName)
+	}
+
+	am.NtChallengeResponse = computeNtlmV2Response(ntlmV2Hash,
+		cm.ServerChallenge[:], clientChallenge, timestamp, cm.TargetInfoRaw)
+
+	if cm.TargetInfoRaw == nil {
+		am.LmChallengeResponse = computeLmV2Response(ntlmV2Hash,
+			cm.ServerChallenge[:], clientChallenge)
+	}
+	return am.MarshalBinary()
+}
+
+// ProcessChallenge crafts an AUTHENTICATE message in response to the CHALLENGE message that was received from the server.
+// DomainNeeded is ignored, as the function extracts the domain from the username if needed.
+//
+// Deprecated: Use [NewAuthenticateMessage] instead.
+//
+//go:fix inline
+func ProcessChallenge(challengeMessageData []byte, username, password string, domainNeeded bool) ([]byte, error) {
+	return NewAuthenticateMessage(challengeMessageData, username, password, nil)
+}
+
+// ProcessChallengeWithHash is like ProcessChallenge but expects the password to be already hashed.
+// The hash should be provided in hexadecimal format.
+//
+// Deprecated: Use [NewAuthenticateMessage] with [AuthenticateMessageOptions.PasswordHashed] instead.
+//
+//go:fix inline
+func ProcessChallengeWithHash(challengeMessageData []byte, username, hash string) ([]byte, error) {
+	return NewAuthenticateMessage(challengeMessageData, username, hash, &AuthenticateMessageOptions{
+		PasswordHashed: true,
+	})
+}
@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"encoding/base64"
+	"net/http"
+	"strings"
+)
+
+var schemaPreference = [...]string{"NTLM", "Negotiate", "Basic"}
+
+type authheader struct {
+	schema string
+	data   string
+}
+
+// newAuthHeader extracts the authheader from the provided HTTP headers.
+// It selects the most preferred authentication scheme.
+// If no supported scheme is found, it returns an empty authheader.
+func newAuthHeader(req http.Header) authheader {
+	auth := req.Values("Www-Authenticate")
+	preferred, idx := -1, -1
+	for i, s := range auth {
+		for j, schema := range schemaPreference {
+			if s == schema || strings.HasPrefix(s, schema+" ") {
+				if preferred == -1 || j < preferred {
+					preferred = j
+					idx = i
+					break
+				}
+			}
+		}
+	}
+	if idx == -1 {
+		return authheader{}
+	}
+	schema, data, _ := strings.Cut(auth[idx], " ")
+	return authheader{
+		schema: schema,
+		data:   data,
+	}
+}
+
+// isNTLM returns true if the authheader schema is NTLM or Negotiate.
+func (h authheader) isNTLM() bool {
+	return h.schema == "NTLM" || h.schema == "Negotiate"
+}
+
+// isBasic returns true if the authheader schema is Basic.
+func (h authheader) isBasic() bool {
+	return h.schema == "Basic"
+}
+
+// token extracts and decodes the base64 token from the authheader.
+// It returns nil if the schema is not NTLM or Negotiate.
+func (h authheader) token() ([]byte, error) {
+	if !h.isNTLM() {
+		// Schema not supported for token extraction
+		return nil, nil
+	}
+	// RFC4559 4.2 - The token is a base64-encoded value
+	return base64.StdEncoding.DecodeString(h.data)
+}
@@ -0,0 +1,20 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+type avID uint16
+
+const (
+	avIDMsvAvEOL avID = iota
+	avIDMsvAvNbComputerName
+	avIDMsvAvNbDomainName
+	avIDMsvAvDNSComputerName
+	avIDMsvAvDNSDomainName
+	avIDMsvAvDNSTreeName
+	avIDMsvAvFlags
+	avIDMsvAvTimestamp
+	avIDMsvAvSingleHost
+	avIDMsvAvTargetName
+	avIDMsvChannelBindings
+)
@@ -0,0 +1,85 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+)
+
+type challengeMessageFields struct {
+	messageHeader
+	TargetName      varField
+	NegotiateFlags  negotiateFlags
+	ServerChallenge [8]byte
+	_               [8]byte
+	TargetInfo      varField
+}
+
+func (m challengeMessageFields) IsValid() bool {
+	return m.messageHeader.IsValid() && m.MessageType == 2
+}
+
+type challengeMessage struct {
+	challengeMessageFields
+	TargetName    string
+	TargetInfo    map[avID][]byte
+	TargetInfoRaw []byte
+}
+
+func (m *challengeMessage) UnmarshalBinary(data []byte) error {
+	r := bytes.NewReader(data)
+	err := binary.Read(r, binary.LittleEndian, &m.challengeMessageFields)
+	if err != nil {
+		return err
+	}
+	if !m.IsValid() {
+		return fmt.Errorf("message is not a valid challenge message: %+v", m.messageHeader)
+	}
+
+	if m.challengeMessageFields.TargetName.Len > 0 {
+		m.TargetName, err = m.challengeMessageFields.TargetName.ReadStringFrom(data, m.NegotiateFlags.Has(negotiateFlagNTLMSSPNEGOTIATEUNICODE))
+		if err != nil {
+			return err
+		}
+	}
+
+	if m.challengeMessageFields.TargetInfo.Len > 0 {
+		d, err := m.challengeMessageFields.TargetInfo.ReadFrom(data)
+		m.TargetInfoRaw = d
+		if err != nil {
+			return err
+		}
+		m.TargetInfo = make(map[avID][]byte)
+		r := bytes.NewReader(d)
+		for {
+			var id avID
+			var l uint16
+			err = binary.Read(r, binary.LittleEndian, &id)
+			if err != nil {
+				return err
+			}
+			if id == avIDMsvAvEOL {
+				break
+			}
+
+			err = binary.Read(r, binary.LittleEndian, &l)
+			if err != nil {
+				return err
+			}
+			value := make([]byte, l)
+			n, err := r.Read(value)
+			if err != nil {
+				return err
+			}
+			if n != int(l) {
+				return fmt.Errorf("expected to read %d bytes, got only %d", l, n)
+			}
+			m.TargetInfo[id] = value
+		}
+	}
+
+	return nil
+}
@@ -0,0 +1,21 @@
+# MD4 Implementation
+
+This package contains an identical copy of the MD4 hash implementation from Go's extended cryptography package (`golang.org/x/crypto/md4`).
+
+## Why Vendored?
+
+This MD4 implementation is vendored locally to avoid depending on the `golang.org/x/crypto` package, which can introduce version conflicts and dependency management issues in `go.mod`. By maintaining our own copy, we ensure:
+
+- **Stability**: No external dependency version conflicts
+- **Simplicity**: Cleaner `go.mod` file without xcrypto dependency
+- **Control**: Full control over the implementation without external changes
+
+## Source
+
+The original implementation can be found at:
+- Package: `golang.org/x/crypto/md4`
+- Repository: https://github.com/golang/crypto
+
+## Usage
+
+This package is intended for internal use within the go-ntlmssp library only. The MD4 hash algorithm is required for NTLM authentication but should not be used for general cryptographic purposes as MD4 is considered cryptographically broken.
@@ -0,0 +1,113 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package md4 implements the MD4 hash algorithm as defined in RFC 1320.
+package md4
+
+import (
+	"hash"
+)
+
+// The size of an MD4 checksum in bytes.
+const Size = 16
+
+// The blocksize of MD4 in bytes.
+const BlockSize = 64
+
+const (
+	_Chunk = 64
+	_Init0 = 0x67452301
+	_Init1 = 0xEFCDAB89
+	_Init2 = 0x98BADCFE
+	_Init3 = 0x10325476
+)
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+	s   [4]uint32
+	x   [_Chunk]byte
+	nx  int
+	len uint64
+}
+
+func (d *digest) Reset() {
+	d.s[0] = _Init0
+	d.s[1] = _Init1
+	d.s[2] = _Init2
+	d.s[3] = _Init3
+	d.nx = 0
+	d.len = 0
+}
+
+// New returns a new hash.Hash computing the MD4 checksum.
+func New() hash.Hash {
+	d := new(digest)
+	d.Reset()
+	return d
+}
+
+func (d *digest) Size() int { return Size }
+
+func (d *digest) BlockSize() int { return BlockSize }
+
+func (d *digest) Write(p []byte) (nn int, err error) {
+	nn = len(p)
+	d.len += uint64(nn)
+	if d.nx > 0 {
+		n := len(p)
+		if n > _Chunk-d.nx {
+			n = _Chunk - d.nx
+		}
+		for i := 0; i < n; i++ {
+			d.x[d.nx+i] = p[i]
+		}
+		d.nx += n
+		if d.nx == _Chunk {
+			_Block(d, d.x[0:])
+			d.nx = 0
+		}
+		p = p[n:]
+	}
+	n := _Block(d, p)
+	p = p[n:]
+	if len(p) > 0 {
+		d.nx = copy(d.x[:], p)
+	}
+	return
+}
+
+func (d0 *digest) Sum(in []byte) []byte {
+	// Make a copy of d0, so that caller can keep writing and summing.
+	d := new(digest)
+	*d = *d0
+
+	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
+	len := d.len
+	var tmp [64]byte
+	tmp[0] = 0x80
+	if len%64 < 56 {
+		d.Write(tmp[0 : 56-len%64])
+	} else {
+		d.Write(tmp[0 : 64+56-len%64])
+	}
+
+	// Length in bits.
+	len <<= 3
+	for i := uint(0); i < 8; i++ {
+		tmp[i] = byte(len >> (8 * i))
+	}
+	d.Write(tmp[0:8])
+
+	if d.nx != 0 {
+		panic("d.nx != 0")
+	}
+
+	for _, s := range d.s {
+		in = append(in, byte(s>>0))
+		in = append(in, byte(s>>8))
+		in = append(in, byte(s>>16))
+		in = append(in, byte(s>>24))
+	}
+	return in
+}
@@ -0,0 +1,91 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// MD4 block step.
+// In its own file so that a faster assembly or C version
+// can be substituted easily.
+
+package md4
+
+import "math/bits"
+
+var shift1 = []int{3, 7, 11, 19}
+var shift2 = []int{3, 5, 9, 13}
+var shift3 = []int{3, 9, 11, 15}
+
+var xIndex2 = []uint{0, 4, 8, 12, 1, 5, 9, 13, 2, 6, 10, 14, 3, 7, 11, 15}
+var xIndex3 = []uint{0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15}
+
+func _Block(dig *digest, p []byte) int {
+	a := dig.s[0]
+	b := dig.s[1]
+	c := dig.s[2]
+	d := dig.s[3]
+	n := 0
+	var X [16]uint32
+	for len(p) >= _Chunk {
+		aa, bb, cc, dd := a, b, c, d
+
+		j := 0
+		for i := 0; i < 16; i++ {
+			X[i] = uint32(p[j]) | uint32(p[j+1])<<8 | uint32(p[j+2])<<16 | uint32(p[j+3])<<24
+			j += 4
+		}
+
+		// If this needs to be made faster in the future,
+		// the usual trick is to unroll each of these
+		// loops by a factor of 4; that lets you replace
+		// the shift[] lookups with constants and,
+		// with suitable variable renaming in each
+		// unrolled body, delete the a, b, c, d = d, a, b, c
+		// (or you can let the optimizer do the renaming).
+		//
+		// The index variables are uint so that % by a power
+		// of two can be optimized easily by a compiler.
+
+		// Round 1.
+		for i := uint(0); i < 16; i++ {
+			x := i
+			s := shift1[i%4]
+			f := ((c ^ d) & b) ^ d
+			a += f + X[x]
+			a = bits.RotateLeft32(a, s)
+			a, b, c, d = d, a, b, c
+		}
+
+		// Round 2.
+		for i := uint(0); i < 16; i++ {
+			x := xIndex2[i]
+			s := shift2[i%4]
+			g := (b & c) | (b & d) | (c & d)
+			a += g + X[x] + 0x5a827999
+			a = bits.RotateLeft32(a, s)
+			a, b, c, d = d, a, b, c
+		}
+
+		// Round 3.
+		for i := uint(0); i < 16; i++ {
+			x := xIndex3[i]
+			s := shift3[i%4]
+			h := b ^ c ^ d
+			a += h + X[x] + 0x6ed9eba1
+			a = bits.RotateLeft32(a, s)
+			a, b, c, d = d, a, b, c
+		}
+
+		a += aa
+		b += bb
+		c += cc
+		d += dd
+
+		p = p[_Chunk:]
+		n += _Chunk
+	}
+
+	dig.s[0] = a
+	dig.s[1] = b
+	dig.s[2] = c
+	dig.s[3] = d
+	return n
+}
@@ -0,0 +1,24 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"bytes"
+)
+
+var signature = [8]byte{'N', 'T', 'L', 'M', 'S', 'S', 'P', 0}
+
+type messageHeader struct {
+	Signature   [8]byte
+	MessageType uint32
+}
+
+func (h messageHeader) IsValid() bool {
+	return bytes.Equal(h.Signature[:], signature[:]) &&
+		h.MessageType > 0 && h.MessageType < 4
+}
+
+func newMessageHeader(messageType uint32) messageHeader {
+	return messageHeader{signature, messageType}
+}
@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+type negotiateFlags uint32
+
+const (
+	/*A*/ negotiateFlagNTLMSSPNEGOTIATEUNICODE negotiateFlags = 1 << 0
+	/*B*/ negotiateFlagNTLMNEGOTIATEOEM = 1 << 1
+	/*C*/ negotiateFlagNTLMSSPREQUESTTARGET = 1 << 2
+
+	/*D*/
+	negotiateFlagNTLMSSPNEGOTIATESIGN = 1 << 4
+	/*E*/ negotiateFlagNTLMSSPNEGOTIATESEAL = 1 << 5
+	/*F*/ negotiateFlagNTLMSSPNEGOTIATEDATAGRAM = 1 << 6
+	/*G*/ negotiateFlagNTLMSSPNEGOTIATELMKEY = 1 << 7
+
+	/*H*/
+	negotiateFlagNTLMSSPNEGOTIATENTLM = 1 << 9
+
+	/*J*/
+	negotiateFlagANONYMOUS = 1 << 11
+	/*K*/ negotiateFlagNTLMSSPNEGOTIATEOEMDOMAINSUPPLIED = 1 << 12
+	/*L*/ negotiateFlagNTLMSSPNEGOTIATEOEMWORKSTATIONSUPPLIED = 1 << 13
+
+	/*M*/
+	negotiateFlagNTLMSSPNEGOTIATEALWAYSSIGN = 1 << 15
+	/*N*/ negotiateFlagNTLMSSPTARGETTYPEDOMAIN = 1 << 16
+	/*O*/ negotiateFlagNTLMSSPTARGETTYPESERVER = 1 << 17
+
+	/*P*/
+	negotiateFlagNTLMSSPNEGOTIATEEXTENDEDSESSIONSECURITY = 1 << 19
+	/*Q*/ negotiateFlagNTLMSSPNEGOTIATEIDENTIFY = 1 << 20
+
+	/*R*/
+	negotiateFlagNTLMSSPREQUESTNONNTSESSIONKEY = 1 << 22
+	/*S*/ negotiateFlagNTLMSSPNEGOTIATETARGETINFO = 1 << 23
+
+	/*T*/
+	negotiateFlagNTLMSSPNEGOTIATEVERSION = 1 << 25
+
+	/*U*/
+	negotiateFlagNTLMSSPNEGOTIATE128 = 1 << 29
+	/*V*/ negotiateFlagNTLMSSPNEGOTIATEKEYEXCH = 1 << 30
+	/*W*/ negotiateFlagNTLMSSPNEGOTIATE56 = 1 << 31
+)
+
+func (field negotiateFlags) Has(flags negotiateFlags) bool {
+	return field&flags == flags
+}
+
+func (field *negotiateFlags) Unset(flags negotiateFlags) {
+	*field ^= *field & flags
+}
@@ -0,0 +1,73 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"strings"
+)
+
+const expMsgBodyLen = 40
+
+type negotiateMessageFields struct {
+	messageHeader
+	NegotiateFlags negotiateFlags
+
+	Domain      varField
+	Workstation varField
+
+	Version
+}
+
+var defaultFlags = negotiateFlagNTLMSSPNEGOTIATETARGETINFO |
+	negotiateFlagNTLMSSPNEGOTIATE56 |
+	negotiateFlagNTLMSSPNEGOTIATE128 |
+	negotiateFlagNTLMSSPNEGOTIATEUNICODE |
+	negotiateFlagNTLMSSPNEGOTIATEEXTENDEDSESSIONSECURITY |
+	negotiateFlagNTLMSSPNEGOTIATENTLM |
+	negotiateFlagNTLMSSPNEGOTIATEALWAYSSIGN
+
+// NewNegotiateMessage creates a new NEGOTIATE message with the flags that this package supports.
+// Note that domain and workstation refer to the client machine, not the user that is authenticating.
+// It is recommended to leave them empty unless you know which are their correct values.
+//
+// The server may ignore these values, or may use them to infer that the client if running on the
+// same machine.
+func NewNegotiateMessage(domain, workstation string) ([]byte, error) {
+	payloadOffset := expMsgBodyLen
+	flags := defaultFlags
+
+	if domain != "" {
+		flags |= negotiateFlagNTLMSSPNEGOTIATEOEMDOMAINSUPPLIED
+	}
+
+	if workstation != "" {
+		flags |= negotiateFlagNTLMSSPNEGOTIATEOEMWORKSTATIONSUPPLIED
+	}
+
+	msg := negotiateMessageFields{
+		messageHeader:  newMessageHeader(1),
+		NegotiateFlags: flags,
+		Domain:         newVarField(&payloadOffset, len(domain)),
+		Workstation:    newVarField(&payloadOffset, len(workstation)),
+		Version:        DefaultVersion(),
+	}
+
+	b := bytes.Buffer{}
+	if err := binary.Write(&b, binary.LittleEndian, &msg); err != nil {
+		return nil, err
+	}
+	if b.Len() != expMsgBodyLen {
+		return nil, errors.New("incorrect body length")
+	}
+
+	payload := strings.ToUpper(domain + workstation)
+	if _, err := b.WriteString(payload); err != nil {
+		return nil, err
+	}
+
+	return b.Bytes(), nil
+}
@@ -0,0 +1,331 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"bytes"
+	"encoding/base64"
+	"io"
+	"net/http"
+	"strings"
+)
+
+// negotiatorBody wraps an io.ReadSeeker to allow waiting for its closure
+// before rewinding and reusing it.
+type negotiatorBody struct {
+	body     io.ReadSeeker
+	closed   chan struct{}
+	startPos int64
+}
+
+// newNegotiatorBody creates a negotiatorBody from the provided io.Reader.
+// If the body is nil, it returns nil.
+// If the body is already an io.ReadSeeker, it uses it directly.
+// Otherwise, it reads the entire body into memory to allow rewinding.
+func newNegotiatorBody(body io.Reader) (*negotiatorBody, error) {
+	if body == nil {
+		return nil, nil
+	}
+	// Check if body is already seekable to avoid buffering large bodies
+	if seeker, ok := body.(io.ReadSeeker); ok {
+		// Remember the current position
+		startPos, err := seeker.Seek(0, io.SeekCurrent)
+		if err == nil {
+			// Seeking succeeded, use the seekable body directly
+			return &negotiatorBody{
+				body:     seeker,
+				closed:   make(chan struct{}, 1),
+				startPos: startPos,
+			}, nil
+		}
+		// Seeking failed (e.g., pipes), fallback to buffering
+	}
+	// For non-seekable bodies, buffer in memory as required
+	data, err := io.ReadAll(body)
+	if err != nil {
+		return nil, err
+	}
+	return &negotiatorBody{
+		body:   bytes.NewReader(data),
+		closed: make(chan struct{}, 1),
+	}, nil
+}
+
+func (b *negotiatorBody) Read(p []byte) (n int, err error) {
+	if b == nil {
+		return 0, io.EOF
+	}
+	return b.body.Read(p)
+}
+
+// Close signals that the body is no longer needed for the current request.
+// It allows the negotiator to rewind the body for potential reuse.
+// The underlying body is not closed here; use close() for that.
+func (b *negotiatorBody) Close() error {
+	if b == nil {
+		return nil
+	}
+	select {
+	case b.closed <- struct{}{}:
+	default:
+		// Already signaled
+	}
+	return nil
+}
+
+// close closes the underlying body if it implements io.Closer.
+func (b *negotiatorBody) close() {
+	if b == nil {
+		return
+	}
+	if closer, ok := b.body.(io.Closer); ok {
+		_ = closer.Close()
+	}
+}
+
+// rewind rewinds the body to the start position for reuse.
+func (b *negotiatorBody) rewind() error {
+	if b == nil {
+		return nil
+	}
+	// Wait for the body to be closed before rewinding
+	<-b.closed
+	_, err := b.body.Seek(b.startPos, io.SeekStart)
+	return err
+}
+
+// GetDomain extracts the user domain from the username if present.
+//
+// Deprecated: Pass the username directly to [ProcessChallenge], it will handle domain extraction.
+// Don't pass the resulting domain to [NewNegotiateMessage], that function expects the client
+// machine domain, not the user domain.
+func GetDomain(username string) (user string, domain string, domainNeeded bool) {
+	if strings.Contains(username, "\\") {
+		ucomponents := strings.SplitN(username, "\\", 2)
+		domain = ucomponents[0]
+		user = ucomponents[1]
+		domainNeeded = true
+	} else if strings.Contains(username, "@") {
+		user = username
+		domainNeeded = false
+	} else {
+		user = username
+		domainNeeded = true
+	}
+	return user, domain, domainNeeded
+}
+
+// Negotiator is a [net/http.RoundTripper] decorator that automatically
+// converts basic authentication to NTLM/Negotiate authentication when appropriate.
+//
+// The credentials must be set using [net/http.Request.SetBasicAuth] on a per-request basis.
+//
+// By default, no credentials will be sent to the server unless it requests
+// Basic authentication and [Negotiator.AllowBasicAuth] is set to true.
+type Negotiator struct {
+	// RoundTripper is the underlying round tripper to use.
+	// If nil, http.DefaultTransport is used.
+	http.RoundTripper
+
+	// AllowBasicAuth controls whether to send Basic authentication credentials
+	// if the server requests it.
+	//
+	// If false (default), Basic authentication requests are ignored
+	// and only NTLM/Negotiate authentication is performed.
+	// If true, Basic authentication requests are honored.
+	//
+	// Only set this to true if you trust the server you are connecting to.
+	// Basic authentication sends the credentials in clear text and may be
+	// vulnerable to man-in-the-middle attacks and compromised servers.
+	AllowBasicAuth bool
+
+	// WorkstationDomain is the domain of the client machine.
+	// It is normally not needed to set this field.
+	// It is passed to the negotiate message.
+	WorkstationDomain string
+
+	// WorkstationName is the workstation name of the client machine.
+	// It is passed to the negotiate and authenticate messages.
+	// Useful for auditing purposes on the server side.
+	WorkstationName string
+}
+
+// RoundTrip sends the request to the server, handling any authentication
+// re-sends as needed.
+func (l Negotiator) RoundTrip(req *http.Request) (*http.Response, error) {
+	// Use default round tripper if not provided
+	rt := l.RoundTripper
+	if rt == nil {
+		rt = http.DefaultTransport
+	}
+
+	// If it is not basic auth, just round trip the request as usual
+	username, password, ok := req.BasicAuth()
+	if !ok {
+		return rt.RoundTrip(req)
+	}
+	id := identity{
+		username: username,
+		password: password,
+	}
+
+	req = req.Clone(req.Context()) // Clone the request to avoid modifying the original
+
+	// We need to buffer or seek the request body to handle authentication challenges
+	// that require resending the body multiple times during the NTLM handshake.
+	body, err := newNegotiatorBody(req.Body)
+	if err != nil {
+		if req.Body != nil {
+			_ = req.Body.Close()
+		}
+		return nil, err
+	}
+	defer body.close()
+
+	// First try anonymous, in case the server still finds us authenticated from previous traffic
+	req.Body = body
+	req.Header.Del("Authorization")
+	resp, err := rt.RoundTrip(req)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusUnauthorized {
+		// No authentication required, return the response as is
+		return resp, nil
+	}
+
+	// Note that from here on, the response returned in case of error or unsuccessful
+	// negotiation is the one we just got from the server. This is to allow the caller
+	// to do its own handling in case we can't do it in this roundtrip.
+	originalResp := resp
+
+	resauth := newAuthHeader(resp.Header)
+	if l.AllowBasicAuth && resauth.isBasic() {
+		// Basic auth requested instead of NTLM/Negotiate.
+		//
+		// Rewind the body, we will resend it.
+		if body.rewind() != nil {
+			return originalResp, nil
+		}
+		req.SetBasicAuth(id.username, id.password)
+		resp, err := rt.RoundTrip(req)
+		if err != nil {
+			return originalResp, nil
+		}
+		if resp.StatusCode != http.StatusUnauthorized {
+			// Basic auth succeeded, return the new response
+			drainResponse(originalResp)
+			return resp, nil
+		}
+		resauth = newAuthHeader(resp.Header)
+		if !resauth.isNTLM() {
+			// No NTLM/Negotiate requested, return the response as is
+			return resp, nil
+		}
+		// Server upgraded from Basic to NTLM/Negotiate (rare but possible)
+		drainResponse(resp)
+		// After Basic-to-NTLM upgrade, update originalResp to the NTLM-triggering response
+		originalResp = resp
+	} else if !resauth.isNTLM() {
+		// No NTLM/Negotiate requested, return the response as is
+		return originalResp, nil
+	}
+
+	// Server requested Negotiate/NTLM, start handshake
+
+	// First step: send negotiate message
+	resp = clientHandshake(rt, req, resauth.schema, l.WorkstationDomain, l.WorkstationName)
+	if resp == nil {
+		return originalResp, nil
+	}
+	if resp.StatusCode != http.StatusUnauthorized {
+		// We are expecting a 401 with challenge, but the server responded differently,
+		// maybe it even accepted our negotiate message without further challenge, which is
+		// valid per the spec (RFC 4559 Section 5).
+		// Return the response as is, negotiation is over.
+		drainResponse(originalResp)
+		return resp, nil
+	}
+	resauth = newAuthHeader(resp.Header)
+	drainResponse(resp)
+
+	// Second step: process challenge and resend the original body with the authenticate message
+	resp = completeHandshake(rt, resauth, req, id, l.WorkstationName)
+	if resp == nil {
+		return originalResp, nil
+	}
+	// We could return the original response in case of 401 again, but at this point
+	// it's better to return the latest response from the server, as it might be the case
+	// that we are really not authorized.
+	drainResponse(originalResp) // Done with the original response
+	return resp, nil
+}
+
+type identity struct {
+	username string
+	password string
+}
+
+func drainResponse(res *http.Response) {
+	// Drain body and close it to allow reusing the connection
+	_, _ = io.Copy(io.Discard, res.Body)
+	_ = res.Body.Close()
+}
+
+func rewindBody(req *http.Request) error {
+	if req.Body == nil {
+		return nil
+	}
+	if nb, ok := req.Body.(*negotiatorBody); ok {
+		return nb.rewind()
+	}
+	return nil
+}
+
+func clientHandshake(rt http.RoundTripper, req *http.Request, schema string, domain, workstation string) *http.Response {
+	if rewindBody(req) != nil {
+		return nil
+	}
+	auth, err := NewNegotiateMessage(domain, workstation)
+	if err != nil {
+		return nil
+	}
+	req.Header.Set("Authorization", schema+" "+base64.StdEncoding.EncodeToString(auth))
+	res, err := rt.RoundTrip(req)
+	if err != nil {
+		return nil
+	}
+	return res
+}
+
+func completeHandshake(rt http.RoundTripper, resauth authheader, req *http.Request, id identity, workstation string) *http.Response {
+	if rewindBody(req) != nil {
+		return nil
+	}
+	challenge, err := resauth.token()
+	if err != nil {
+		return nil
+	}
+	if !resauth.isNTLM() || len(challenge) == 0 {
+		// The only expected schema here is NTLM/Negotiate with a challenge token,
+		// otherwise the negotiation is over.
+		return nil
+	}
+	var opts *AuthenticateMessageOptions
+	if workstation != "" {
+		opts = &AuthenticateMessageOptions{
+			WorkstationName: workstation,
+		}
+	}
+	auth, err := NewAuthenticateMessage(challenge, id.username, id.password, opts)
+	if err != nil {
+		return nil
+	}
+	req.Header.Set("Authorization", resauth.schema+" "+base64.StdEncoding.EncodeToString(auth))
+	resp, err := rt.RoundTrip(req)
+	if err != nil {
+		return nil
+	}
+	return resp
+}
@@ -0,0 +1,57 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+// Protocol details from https://msdn.microsoft.com/en-us/library/cc236621.aspx,
+// implementation hints from http://davenport.sourceforge.net/ntlm.html .
+// This package only implements authentication, no key exchange or encryption. It
+// only supports Unicode (UTF16LE) encoding of protocol strings, no OEM encoding.
+// This package implements NTLMv2.
+package ntlmssp
+
+import (
+	"crypto/hmac"
+	"crypto/md5"
+	"strings"
+
+	"github.com/Azure/go-ntlmssp/internal/md4"
+)
+
+func getNtlmV2Hash(password, username, domain string) []byte {
+	return getNtlmV2Hashed(getNtlmHash(password), username, domain)
+}
+
+func getNtlmV2Hashed(ntlmHash []byte, username, domain string) []byte {
+	return hmacMd5(ntlmHash, toUnicode(strings.ToUpper(username)+domain))
+}
+
+func getNtlmHash(password string) []byte {
+	hash := md4.New()
+	hash.Write(toUnicode(password))
+	return hash.Sum(nil)
+}
+
+func computeNtlmV2Response(ntlmV2Hash, serverChallenge, clientChallenge,
+	timestamp, targetInfo []byte,
+) []byte {
+	temp := []byte{1, 1, 0, 0, 0, 0, 0, 0}
+	temp = append(temp, timestamp...)
+	temp = append(temp, clientChallenge...)
+	temp = append(temp, 0, 0, 0, 0)
+	temp = append(temp, targetInfo...)
+	temp = append(temp, 0, 0, 0, 0)
+
+	NTProofStr := hmacMd5(ntlmV2Hash, serverChallenge, temp)
+	return append(NTProofStr, temp...)
+}
+
+func computeLmV2Response(ntlmV2Hash, serverChallenge, clientChallenge []byte) []byte {
+	return append(hmacMd5(ntlmV2Hash, serverChallenge, clientChallenge), clientChallenge...)
+}
+
+func hmacMd5(key []byte, data ...[]byte) []byte {
+	mac := hmac.New(md5.New, key)
+	for _, d := range data {
+		mac.Write(d)
+	}
+	return mac.Sum(nil)
+}
@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"unicode/utf16"
+)
+
+// helper func's for dealing with Windows Unicode (UTF16LE)
+
+func fromUnicode(d []byte) (string, error) {
+	if len(d)%2 > 0 {
+		return "", errors.New("unicode (UTF 16 LE) specified, but uneven data length")
+	}
+	s := make([]uint16, len(d)/2)
+	err := binary.Read(bytes.NewReader(d), binary.LittleEndian, &s)
+	if err != nil {
+		return "", err
+	}
+	return string(utf16.Decode(s)), nil
+}
+
+func toUnicode(s string) []byte {
+	uints := utf16.Encode([]rune(s))
+	b := bytes.Buffer{}
+	_ = binary.Write(&b, binary.LittleEndian, &uints)
+	return b.Bytes()
+}
@@ -0,0 +1,47 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"errors"
+)
+
+type varField struct {
+	Len          uint16
+	MaxLen       uint16
+	BufferOffset uint32
+}
+
+func (f varField) ReadFrom(buffer []byte) ([]byte, error) {
+	// f.Len is controlled by the sender, so we need to check that
+	// it doesn't cause an overflow when added to f.BufferOffset.
+	start := uint64(f.BufferOffset)
+	end := start + uint64(f.Len)
+	if end < start || end > uint64(len(buffer)) {
+		return nil, errors.New("error reading data, varField extends beyond buffer")
+	}
+	return buffer[int(start):int(end)], nil
+}
+
+func (f varField) ReadStringFrom(buffer []byte, unicode bool) (string, error) {
+	d, err := f.ReadFrom(buffer)
+	if err != nil {
+		return "", err
+	}
+	if unicode { // UTF-16LE encoding scheme
+		return fromUnicode(d)
+	}
+	// OEM encoding, close enough to ASCII, since no code page is specified
+	return string(d), err
+}
+
+func newVarField(ptr *int, fieldsize int) varField {
+	f := varField{
+		Len:          uint16(fieldsize),
+		MaxLen:       uint16(fieldsize),
+		BufferOffset: uint32(*ptr),
+	}
+	*ptr += fieldsize
+	return f
+}
@@ -0,0 +1,23 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+// Version is a struct representing https://msdn.microsoft.com/en-us/library/cc236654.aspx
+type Version struct {
+	ProductMajorVersion uint8
+	ProductMinorVersion uint8
+	ProductBuild        uint16
+	_                   [3]byte
+	NTLMRevisionCurrent uint8
+}
+
+// DefaultVersion returns a Version with "sensible" defaults (Windows 7)
+func DefaultVersion() Version {
+	return Version{
+		ProductMajorVersion: 6,
+		ProductMinorVersion: 1,
+		ProductBuild:        7601,
+		NTLMRevisionCurrent: 15,
+	}
+}
@@ -0,0 +1,2 @@
+/toml.test
+/toml-test
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2013 TOML authors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
@@ -0,0 +1,120 @@
+TOML stands for Tom's Obvious, Minimal Language. This Go package provides a
+reflection interface similar to Go's standard library `json` and `xml` packages.
+
+Compatible with TOML version [v1.1.0](https://toml.io/en/v1.1.0).
+
+Documentation: https://pkg.go.dev/github.com/BurntSushi/toml
+
+See the [releases page](https://github.com/BurntSushi/toml/releases) for a
+changelog; this information is also in the git tag annotations (e.g. `git show
+v0.4.0`).
+
+This library requires Go 1.18 or newer; add it to your go.mod with:
+
+    % go get github.com/BurntSushi/toml@latest
+
+It also comes with a TOML validator CLI tool:
+
+    % go install github.com/BurntSushi/toml/cmd/tomlv@latest
+    % tomlv some-toml-file.toml
+
+### Examples
+For the simplest example, consider some TOML file as just a list of keys and
+values:
+
+```toml
+Age = 25
+Cats = [ "Cauchy", "Plato" ]
+Pi = 3.14
+Perfection = [ 6, 28, 496, 8128 ]
+DOB = 1987-07-05T05:45:00Z
+```
+
+Which can be decoded with:
+
+```go
+type Config struct {
+	Age        int
+	Cats       []string
+	Pi         float64
+	Perfection []int
+	DOB        time.Time
+}
+
+var conf Config
+_, err := toml.Decode(tomlData, &conf)
+```
+
+You can also use struct tags if your struct field name doesn't map to a TOML key
+value directly:
+
+```toml
+some_key_NAME = "wat"
+```
+
+```go
+type TOML struct {
+    ObscureKey string `toml:"some_key_NAME"`
+}
+```
+
+Beware that like other decoders **only exported fields** are considered when
+encoding and decoding; private fields are silently ignored.
+
+### Using the `Marshaler` and `encoding.TextUnmarshaler` interfaces
+Here's an example that automatically parses values in a `mail.Address`:
+
+```toml
+contacts = [
+    "Donald Duck <donald@duckburg.com>",
+    "Scrooge McDuck <scrooge@duckburg.com>",
+]
+```
+
+Can be decoded with:
+
+```go
+// Create address type which satisfies the encoding.TextUnmarshaler interface.
+type address struct {
+	*mail.Address
+}
+
+func (a *address) UnmarshalText(text []byte) error {
+	var err error
+	a.Address, err = mail.ParseAddress(string(text))
+	return err
+}
+
+// Decode it.
+func decode() {
+	blob := `
+		contacts = [
+			"Donald Duck <donald@duckburg.com>",
+			"Scrooge McDuck <scrooge@duckburg.com>",
+		]
+	`
+
+	var contacts struct {
+		Contacts []address
+	}
+
+	_, err := toml.Decode(blob, &contacts)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, c := range contacts.Contacts {
+		fmt.Printf("%#v\n", c.Address)
+	}
+
+	// Output:
+	// &mail.Address{Name:"Donald Duck", Address:"donald@duckburg.com"}
+	// &mail.Address{Name:"Scrooge McDuck", Address:"scrooge@duckburg.com"}
+}
+```
+
+To target TOML specifically you can implement `UnmarshalTOML` TOML interface in
+a similar way.
+
+### More complex usage
+See the [`_example/`](/_example) directory for a more complex example.
@@ -0,0 +1,645 @@
+package toml
+
+import (
+	"bytes"
+	"encoding"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/fs"
+	"math"
+	"os"
+	"reflect"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Unmarshaler is the interface implemented by objects that can unmarshal a
+// TOML description of themselves.
+type Unmarshaler interface {
+	UnmarshalTOML(any) error
+}
+
+// Unmarshal decodes the contents of data in TOML format into a pointer v.
+//
+// See [Decoder] for a description of the decoding process.
+func Unmarshal(data []byte, v any) error {
+	_, err := NewDecoder(bytes.NewReader(data)).Decode(v)
+	return err
+}
+
+// Decode the TOML data in to the pointer v.
+//
+// See [Decoder] for a description of the decoding process.
+func Decode(data string, v any) (MetaData, error) {
+	return NewDecoder(strings.NewReader(data)).Decode(v)
+}
+
+// DecodeFile reads the contents of a file and decodes it with [Decode].
+func DecodeFile(path string, v any) (MetaData, error) {
+	fp, err := os.Open(path)
+	if err != nil {
+		return MetaData{}, err
+	}
+	defer fp.Close()
+	return NewDecoder(fp).Decode(v)
+}
+
+// DecodeFS reads the contents of a file from [fs.FS] and decodes it with
+// [Decode].
+func DecodeFS(fsys fs.FS, path string, v any) (MetaData, error) {
+	fp, err := fsys.Open(path)
+	if err != nil {
+		return MetaData{}, err
+	}
+	defer fp.Close()
+	return NewDecoder(fp).Decode(v)
+}
+
+// Primitive is a TOML value that hasn't been decoded into a Go value.
+//
+// This type can be used for any value, which will cause decoding to be delayed.
+// You can use [PrimitiveDecode] to "manually" decode these values.
+//
+// NOTE: The underlying representation of a `Primitive` value is subject to
+// change. Do not rely on it.
+//
+// NOTE: Primitive values are still parsed, so using them will only avoid the
+// overhead of reflection. They can be useful when you don't know the exact type
+// of TOML data until runtime.
+type Primitive struct {
+	undecoded any
+	context   Key
+}
+
+// The significand precision for float32 and float64 is 24 and 53 bits; this is
+// the range a natural number can be stored in a float without loss of data.
+const (
+	maxSafeFloat32Int = 16777215                // 2^24-1
+	maxSafeFloat64Int = int64(9007199254740991) // 2^53-1
+)
+
+// Decoder decodes TOML data.
+//
+// TOML tables correspond to Go structs or maps; they can be used
+// interchangeably, but structs offer better type safety.
+//
+// TOML table arrays correspond to either a slice of structs or a slice of maps.
+//
+// TOML datetimes correspond to [time.Time]. Local datetimes are parsed in the
+// local timezone.
+//
+// [time.Duration] types are treated as nanoseconds if the TOML value is an
+// integer, or they're parsed with time.ParseDuration() if they're strings.
+//
+// All other TOML types (float, string, int, bool and array) correspond to the
+// obvious Go types.
+//
+// An exception to the above rules is if a type implements the TextUnmarshaler
+// interface, in which case any primitive TOML value (floats, strings, integers,
+// booleans, datetimes) will be converted to a []byte and given to the value's
+// UnmarshalText method. See the Unmarshaler example for a demonstration with
+// email addresses.
+//
+// # Key mapping
+//
+// TOML keys can map to either keys in a Go map or field names in a Go struct.
+// The special `toml` struct tag can be used to map TOML keys to struct fields
+// that don't match the key name exactly (see the example). A case insensitive
+// match to struct names will be tried if an exact match can't be found.
+//
+// The mapping between TOML values and Go values is loose. That is, there may
+// exist TOML values that cannot be placed into your representation, and there
+// may be parts of your representation that do not correspond to TOML values.
+// This loose mapping can be made stricter by using the IsDefined and/or
+// Undecoded methods on the MetaData returned.
+//
+// This decoder does not handle cyclic types. Decode will not terminate if a
+// cyclic type is passed.
+type Decoder struct {
+	r io.Reader
+}
+
+// NewDecoder creates a new Decoder.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: r}
+}
+
+var (
+	unmarshalToml = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
+	unmarshalText = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+	primitiveType = reflect.TypeOf((*Primitive)(nil)).Elem()
+)
+
+// Decode TOML data in to the pointer `v`.
+func (dec *Decoder) Decode(v any) (MetaData, error) {
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr {
+		s := "%q"
+		if reflect.TypeOf(v) == nil {
+			s = "%v"
+		}
+
+		return MetaData{}, fmt.Errorf("toml: cannot decode to non-pointer "+s, reflect.TypeOf(v))
+	}
+	if rv.IsNil() {
+		return MetaData{}, fmt.Errorf("toml: cannot decode to nil value of %q", reflect.TypeOf(v))
+	}
+
+	// Check if this is a supported type: struct, map, any, or something that
+	// implements UnmarshalTOML or UnmarshalText.
+	rv = indirect(rv)
+	rt := rv.Type()
+	if rv.Kind() != reflect.Struct && rv.Kind() != reflect.Map &&
+		!(rv.Kind() == reflect.Interface && rv.NumMethod() == 0) &&
+		!rt.Implements(unmarshalToml) && !rt.Implements(unmarshalText) {
+		return MetaData{}, fmt.Errorf("toml: cannot decode to type %s", rt)
+	}
+
+	// TODO: parser should read from io.Reader? Or at the very least, make it
+	// read from []byte rather than string
+	data, err := io.ReadAll(dec.r)
+	if err != nil {
+		return MetaData{}, err
+	}
+
+	p, err := parse(string(data))
+	if err != nil {
+		return MetaData{}, err
+	}
+
+	md := MetaData{
+		mapping: p.mapping,
+		keyInfo: p.keyInfo,
+		keys:    p.ordered,
+		decoded: make(map[string]struct{}, len(p.ordered)),
+		context: nil,
+		data:    data,
+	}
+	return md, md.unify(p.mapping, rv)
+}
+
+// PrimitiveDecode is just like the other Decode* functions, except it decodes a
+// TOML value that has already been parsed. Valid primitive values can *only* be
+// obtained from values filled by the decoder functions, including this method.
+// (i.e., v may contain more [Primitive] values.)
+//
+// Meta data for primitive values is included in the meta data returned by the
+// Decode* functions with one exception: keys returned by the Undecoded method
+// will only reflect keys that were decoded. Namely, any keys hidden behind a
+// Primitive will be considered undecoded. Executing this method will update the
+// undecoded keys in the meta data. (See the example.)
+func (md *MetaData) PrimitiveDecode(primValue Primitive, v any) error {
+	md.context = primValue.context
+	defer func() { md.context = nil }()
+	return md.unify(primValue.undecoded, rvalue(v))
+}
+
+// markDecodedRecursive is a helper to mark any key under the given tmap as
+// decoded, recursing as needed
+func markDecodedRecursive(md *MetaData, tmap map[string]any) {
+	for key := range tmap {
+		md.decoded[md.context.add(key).String()] = struct{}{}
+		if tmap, ok := tmap[key].(map[string]any); ok {
+			md.context = append(md.context, key)
+			markDecodedRecursive(md, tmap)
+			md.context = md.context[0 : len(md.context)-1]
+		}
+		if tarr, ok := tmap[key].([]map[string]any); ok {
+			for _, elm := range tarr {
+				md.context = append(md.context, key)
+				markDecodedRecursive(md, elm)
+				md.context = md.context[0 : len(md.context)-1]
+			}
+		}
+	}
+}
+
+// unify performs a sort of type unification based on the structure of `rv`,
+// which is the client representation.
+//
+// Any type mismatch produces an error. Finding a type that we don't know
+// how to handle produces an unsupported type error.
+func (md *MetaData) unify(data any, rv reflect.Value) error {
+	// Special case. Look for a `Primitive` value.
+	// TODO: #76 would make this superfluous after implemented.
+	if rv.Type() == primitiveType {
+		// Save the undecoded data and the key context into the primitive
+		// value.
+		context := make(Key, len(md.context))
+		copy(context, md.context)
+		rv.Set(reflect.ValueOf(Primitive{
+			undecoded: data,
+			context:   context,
+		}))
+		return nil
+	}
+
+	rvi := rv.Interface()
+	if v, ok := rvi.(Unmarshaler); ok {
+		err := v.UnmarshalTOML(data)
+		if err != nil {
+			return md.parseErr(err)
+		}
+		// Assume the Unmarshaler decoded everything, so mark all keys under
+		// this table as decoded.
+		if tmap, ok := data.(map[string]any); ok {
+			markDecodedRecursive(md, tmap)
+		}
+		if aot, ok := data.([]map[string]any); ok {
+			for _, tmap := range aot {
+				markDecodedRecursive(md, tmap)
+			}
+		}
+		return nil
+	}
+	if v, ok := rvi.(encoding.TextUnmarshaler); ok {
+		return md.unifyText(data, v)
+	}
+
+	// TODO:
+	// The behavior here is incorrect whenever a Go type satisfies the
+	// encoding.TextUnmarshaler interface but also corresponds to a TOML hash or
+	// array. In particular, the unmarshaler should only be applied to primitive
+	// TOML values. But at this point, it will be applied to all kinds of values
+	// and produce an incorrect error whenever those values are hashes or arrays
+	// (including arrays of tables).
+
+	k := rv.Kind()
+
+	if k >= reflect.Int && k <= reflect.Uint64 {
+		return md.unifyInt(data, rv)
+	}
+	switch k {
+	case reflect.Struct:
+		return md.unifyStruct(data, rv)
+	case reflect.Map:
+		return md.unifyMap(data, rv)
+	case reflect.Array:
+		return md.unifyArray(data, rv)
+	case reflect.Slice:
+		return md.unifySlice(data, rv)
+	case reflect.String:
+		return md.unifyString(data, rv)
+	case reflect.Bool:
+		return md.unifyBool(data, rv)
+	case reflect.Interface:
+		if rv.NumMethod() > 0 { /// Only empty interfaces are supported.
+			return md.e("unsupported type %s", rv.Type())
+		}
+		return md.unifyAnything(data, rv)
+	case reflect.Float32, reflect.Float64:
+		return md.unifyFloat64(data, rv)
+	}
+	return md.e("unsupported type %s", rv.Kind())
+}
+
+func (md *MetaData) unifyStruct(mapping any, rv reflect.Value) error {
+	tmap, ok := mapping.(map[string]any)
+	if !ok {
+		if mapping == nil {
+			return nil
+		}
+		return md.e("type mismatch for %s: expected table but found %s", rv.Type().String(), fmtType(mapping))
+	}
+
+	for key, datum := range tmap {
+		var f *field
+		fields := cachedTypeFields(rv.Type())
+		for i := range fields {
+			ff := &fields[i]
+			if ff.name == key {
+				f = ff
+				break
+			}
+			if f == nil && strings.EqualFold(ff.name, key) {
+				f = ff
+			}
+		}
+		if f != nil {
+			subv := rv
+			for _, i := range f.index {
+				subv = indirect(subv.Field(i))
+			}
+
+			if isUnifiable(subv) {
+				md.decoded[md.context.add(key).String()] = struct{}{}
+				md.context = append(md.context, key)
+
+				err := md.unify(datum, subv)
+				if err != nil {
+					return err
+				}
+				md.context = md.context[0 : len(md.context)-1]
+			} else if f.name != "" {
+				return md.e("cannot write unexported field %s.%s", rv.Type().String(), f.name)
+			}
+		}
+	}
+	return nil
+}
+
+func (md *MetaData) unifyMap(mapping any, rv reflect.Value) error {
+	keyType := rv.Type().Key().Kind()
+	if keyType != reflect.String && keyType != reflect.Interface {
+		return fmt.Errorf("toml: cannot decode to a map with non-string key type (%s in %q)",
+			keyType, rv.Type())
+	}
+
+	tmap, ok := mapping.(map[string]any)
+	if !ok {
+		if tmap == nil {
+			return nil
+		}
+		return md.badtype("map", mapping)
+	}
+	if rv.IsNil() {
+		rv.Set(reflect.MakeMap(rv.Type()))
+	}
+	for k, v := range tmap {
+		md.decoded[md.context.add(k).String()] = struct{}{}
+		md.context = append(md.context, k)
+
+		rvval := reflect.Indirect(reflect.New(rv.Type().Elem()))
+
+		err := md.unify(v, indirect(rvval))
+		if err != nil {
+			return err
+		}
+		md.context = md.context[0 : len(md.context)-1]
+
+		rvkey := indirect(reflect.New(rv.Type().Key()))
+
+		switch keyType {
+		case reflect.Interface:
+			rvkey.Set(reflect.ValueOf(k))
+		case reflect.String:
+			rvkey.SetString(k)
+		}
+
+		rv.SetMapIndex(rvkey, rvval)
+	}
+	return nil
+}
+
+func (md *MetaData) unifyArray(data any, rv reflect.Value) error {
+	datav := reflect.ValueOf(data)
+	if datav.Kind() != reflect.Slice {
+		if !datav.IsValid() {
+			return nil
+		}
+		return md.badtype("slice", data)
+	}
+	if l := datav.Len(); l != rv.Len() {
+		return md.e("expected array length %d; got TOML array of length %d", rv.Len(), l)
+	}
+	return md.unifySliceArray(datav, rv)
+}
+
+func (md *MetaData) unifySlice(data any, rv reflect.Value) error {
+	datav := reflect.ValueOf(data)
+	if datav.Kind() != reflect.Slice {
+		if !datav.IsValid() {
+			return nil
+		}
+		return md.badtype("slice", data)
+	}
+	n := datav.Len()
+	if rv.IsNil() || rv.Cap() < n {
+		rv.Set(reflect.MakeSlice(rv.Type(), n, n))
+	}
+	rv.SetLen(n)
+	return md.unifySliceArray(datav, rv)
+}
+
+func (md *MetaData) unifySliceArray(data, rv reflect.Value) error {
+	l := data.Len()
+	for i := 0; i < l; i++ {
+		err := md.unify(data.Index(i).Interface(), indirect(rv.Index(i)))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (md *MetaData) unifyString(data any, rv reflect.Value) error {
+	_, ok := rv.Interface().(json.Number)
+	if ok {
+		if i, ok := data.(int64); ok {
+			rv.SetString(strconv.FormatInt(i, 10))
+		} else if f, ok := data.(float64); ok {
+			rv.SetString(strconv.FormatFloat(f, 'g', -1, 64))
+		} else {
+			return md.badtype("string", data)
+		}
+		return nil
+	}
+
+	if s, ok := data.(string); ok {
+		rv.SetString(s)
+		return nil
+	}
+	return md.badtype("string", data)
+}
+
+func (md *MetaData) unifyFloat64(data any, rv reflect.Value) error {
+	rvk := rv.Kind()
+
+	if num, ok := data.(float64); ok {
+		switch rvk {
+		case reflect.Float32:
+			if num < -math.MaxFloat32 || num > math.MaxFloat32 {
+				return md.parseErr(errParseRange{i: num, size: rvk.String()})
+			}
+			fallthrough
+		case reflect.Float64:
+			rv.SetFloat(num)
+		default:
+			panic("bug")
+		}
+		return nil
+	}
+
+	if num, ok := data.(int64); ok {
+		if (rvk == reflect.Float32 && (num < -maxSafeFloat32Int || num > maxSafeFloat32Int)) ||
+			(rvk == reflect.Float64 && (num < -maxSafeFloat64Int || num > maxSafeFloat64Int)) {
+			return md.parseErr(errUnsafeFloat{i: num, size: rvk.String()})
+		}
+		rv.SetFloat(float64(num))
+		return nil
+	}
+
+	return md.badtype("float", data)
+}
+
+func (md *MetaData) unifyInt(data any, rv reflect.Value) error {
+	_, ok := rv.Interface().(time.Duration)
+	if ok {
+		// Parse as string duration, and fall back to regular integer parsing
+		// (as nanosecond) if this is not a string.
+		if s, ok := data.(string); ok {
+			dur, err := time.ParseDuration(s)
+			if err != nil {
+				return md.parseErr(errParseDuration{s})
+			}
+			rv.SetInt(int64(dur))
+			return nil
+		}
+	}
+
+	num, ok := data.(int64)
+	if !ok {
+		return md.badtype("integer", data)
+	}
+
+	rvk := rv.Kind()
+	switch {
+	case rvk >= reflect.Int && rvk <= reflect.Int64:
+		if (rvk == reflect.Int8 && (num < math.MinInt8 || num > math.MaxInt8)) ||
+			(rvk == reflect.Int16 && (num < math.MinInt16 || num > math.MaxInt16)) ||
+			(rvk == reflect.Int32 && (num < math.MinInt32 || num > math.MaxInt32)) {
+			return md.parseErr(errParseRange{i: num, size: rvk.String()})
+		}
+		rv.SetInt(num)
+	case rvk >= reflect.Uint && rvk <= reflect.Uint64:
+		unum := uint64(num)
+		if rvk == reflect.Uint8 && (num < 0 || unum > math.MaxUint8) ||
+			rvk == reflect.Uint16 && (num < 0 || unum > math.MaxUint16) ||
+			rvk == reflect.Uint32 && (num < 0 || unum > math.MaxUint32) {
+			return md.parseErr(errParseRange{i: num, size: rvk.String()})
+		}
+		rv.SetUint(unum)
+	default:
+		panic("unreachable")
+	}
+	return nil
+}
+
+func (md *MetaData) unifyBool(data any, rv reflect.Value) error {
+	if b, ok := data.(bool); ok {
+		rv.SetBool(b)
+		return nil
+	}
+	return md.badtype("boolean", data)
+}
+
+func (md *MetaData) unifyAnything(data any, rv reflect.Value) error {
+	rv.Set(reflect.ValueOf(data))
+	return nil
+}
+
+func (md *MetaData) unifyText(data any, v encoding.TextUnmarshaler) error {
+	var s string
+	switch sdata := data.(type) {
+	case Marshaler:
+		text, err := sdata.MarshalTOML()
+		if err != nil {
+			return err
+		}
+		s = string(text)
+	case encoding.TextMarshaler:
+		text, err := sdata.MarshalText()
+		if err != nil {
+			return err
+		}
+		s = string(text)
+	case fmt.Stringer:
+		s = sdata.String()
+	case string:
+		s = sdata
+	case bool:
+		s = fmt.Sprintf("%v", sdata)
+	case int64:
+		s = fmt.Sprintf("%d", sdata)
+	case float64:
+		s = fmt.Sprintf("%f", sdata)
+	default:
+		return md.badtype("primitive (string-like)", data)
+	}
+	if err := v.UnmarshalText([]byte(s)); err != nil {
+		return md.parseErr(err)
+	}
+	return nil
+}
+
+func (md *MetaData) badtype(dst string, data any) error {
+	return md.e("incompatible types: TOML value has type %s; destination has type %s", fmtType(data), dst)
+}
+
+func (md *MetaData) parseErr(err error) error {
+	k := md.context.String()
+	d := string(md.data)
+	return ParseError{
+		Message:  err.Error(),
+		err:      err,
+		LastKey:  k,
+		Position: md.keyInfo[k].pos.withCol(d),
+		Line:     md.keyInfo[k].pos.Line,
+		input:    d,
+	}
+}
+
+func (md *MetaData) e(format string, args ...any) error {
+	f := "toml: "
+	if len(md.context) > 0 {
+		f = fmt.Sprintf("toml: (last key %q): ", md.context)
+		p := md.keyInfo[md.context.String()].pos
+		if p.Line > 0 {
+			f = fmt.Sprintf("toml: line %d (last key %q): ", p.Line, md.context)
+		}
+	}
+	return fmt.Errorf(f+format, args...)
+}
+
+// rvalue returns a reflect.Value of `v`. All pointers are resolved.
+func rvalue(v any) reflect.Value {
+	return indirect(reflect.ValueOf(v))
+}
+
+// indirect returns the value pointed to by a pointer.
+//
+// Pointers are followed until the value is not a pointer. New values are
+// allocated for each nil pointer.
+//
+// An exception to this rule is if the value satisfies an interface of interest
+// to us (like encoding.TextUnmarshaler).
+func indirect(v reflect.Value) reflect.Value {
+	if v.Kind() != reflect.Ptr {
+		if v.CanSet() {
+			pv := v.Addr()
+			pvi := pv.Interface()
+			if _, ok := pvi.(encoding.TextUnmarshaler); ok {
+				return pv
+			}
+			if _, ok := pvi.(Unmarshaler); ok {
+				return pv
+			}
+		}
+		return v
+	}
+	if v.IsNil() {
+		v.Set(reflect.New(v.Type().Elem()))
+	}
+	return indirect(reflect.Indirect(v))
+}
+
+func isUnifiable(rv reflect.Value) bool {
+	if rv.CanSet() {
+		return true
+	}
+	rvi := rv.Interface()
+	if _, ok := rvi.(encoding.TextUnmarshaler); ok {
+		return true
+	}
+	if _, ok := rvi.(Unmarshaler); ok {
+		return true
+	}
+	return false
+}
+
+// fmt %T with "interface {}" replaced with "any", which is far more readable.
+func fmtType(t any) string {
+	return strings.ReplaceAll(fmt.Sprintf("%T", t), "interface {}", "any")
+}
@@ -0,0 +1,29 @@
+package toml
+
+import (
+	"encoding"
+	"io"
+)
+
+// TextMarshaler is an alias for encoding.TextMarshaler.
+//
+// Deprecated: use encoding.TextMarshaler
+type TextMarshaler encoding.TextMarshaler
+
+// TextUnmarshaler is an alias for encoding.TextUnmarshaler.
+//
+// Deprecated: use encoding.TextUnmarshaler
+type TextUnmarshaler encoding.TextUnmarshaler
+
+// DecodeReader is an alias for NewDecoder(r).Decode(v).
+//
+// Deprecated: use NewDecoder(reader).Decode(&value).
+func DecodeReader(r io.Reader, v any) (MetaData, error) { return NewDecoder(r).Decode(v) }
+
+// PrimitiveDecode is an alias for MetaData.PrimitiveDecode().
+//
+// Deprecated: use MetaData.PrimitiveDecode.
+func PrimitiveDecode(primValue Primitive, v any) error {
+	md := MetaData{decoded: make(map[string]struct{})}
+	return md.unify(primValue.undecoded, rvalue(v))
+}
@@ -0,0 +1,8 @@
+// Package toml implements decoding and encoding of TOML files.
+//
+// This package supports TOML v1.0.0, as specified at https://toml.io
+//
+// The github.com/BurntSushi/toml/cmd/tomlv package implements a TOML validator,
+// and can be used to verify if TOML document is valid. It can also be used to
+// print the type of each key.
+package toml
@@ -0,0 +1,789 @@
+package toml
+
+import (
+	"bufio"
+	"bytes"
+	"encoding"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/BurntSushi/toml/internal"
+)
+
+type tomlEncodeError struct{ error }
+
+var (
+	errArrayNilElement = errors.New("toml: cannot encode array with nil element")
+	errNonString       = errors.New("toml: cannot encode a map with non-string key type")
+	errNoKey           = errors.New("toml: top-level values must be Go maps or structs")
+	errAnything        = errors.New("") // used in testing
+)
+
+var dblQuotedReplacer = strings.NewReplacer(
+	"\"", "\\\"",
+	"\\", "\\\\",
+	"\x00", `\u0000`,
+	"\x01", `\u0001`,
+	"\x02", `\u0002`,
+	"\x03", `\u0003`,
+	"\x04", `\u0004`,
+	"\x05", `\u0005`,
+	"\x06", `\u0006`,
+	"\x07", `\u0007`,
+	"\b", `\b`,
+	"\t", `\t`,
+	"\n", `\n`,
+	"\x0b", `\u000b`,
+	"\f", `\f`,
+	"\r", `\r`,
+	"\x0e", `\u000e`,
+	"\x0f", `\u000f`,
+	"\x10", `\u0010`,
+	"\x11", `\u0011`,
+	"\x12", `\u0012`,
+	"\x13", `\u0013`,
+	"\x14", `\u0014`,
+	"\x15", `\u0015`,
+	"\x16", `\u0016`,
+	"\x17", `\u0017`,
+	"\x18", `\u0018`,
+	"\x19", `\u0019`,
+	"\x1a", `\u001a`,
+	"\x1b", `\u001b`,
+	"\x1c", `\u001c`,
+	"\x1d", `\u001d`,
+	"\x1e", `\u001e`,
+	"\x1f", `\u001f`,
+	"\x7f", `\u007f`,
+)
+
+var (
+	marshalToml = reflect.TypeOf((*Marshaler)(nil)).Elem()
+	marshalText = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+	timeType    = reflect.TypeOf((*time.Time)(nil)).Elem()
+)
+
+// Marshaler is the interface implemented by types that can marshal themselves
+// into valid TOML.
+type Marshaler interface {
+	MarshalTOML() ([]byte, error)
+}
+
+// Marshal returns a TOML representation of the Go value.
+//
+// See [Encoder] for a description of the encoding process.
+func Marshal(v any) ([]byte, error) {
+	buff := new(bytes.Buffer)
+	if err := NewEncoder(buff).Encode(v); err != nil {
+		return nil, err
+	}
+	return buff.Bytes(), nil
+}
+
+// Encoder encodes a Go to a TOML document.
+//
+// The mapping between Go values and TOML values should be precisely the same as
+// for [Decode].
+//
+// time.Time is encoded as a RFC 3339 string, and time.Duration as its string
+// representation.
+//
+// The [Marshaler] and [encoding.TextMarshaler] interfaces are supported to
+// encoding the value as custom TOML.
+//
+// If you want to write arbitrary binary data then you will need to use
+// something like base64 since TOML does not have any binary types.
+//
+// When encoding TOML hashes (Go maps or structs), keys without any sub-hashes
+// are encoded first.
+//
+// Go maps will be sorted alphabetically by key for deterministic output.
+//
+// The toml struct tag can be used to provide the key name; if omitted the
+// struct field name will be used. If the "omitempty" option is present the
+// following value will be skipped:
+//
+//   - arrays, slices, maps, and string with len of 0
+//   - struct with all zero values
+//   - bool false
+//
+// If omitzero is given all int and float types with a value of 0 will be
+// skipped.
+//
+// Encoding Go values without a corresponding TOML representation will return an
+// error. Examples of this includes maps with non-string keys, slices with nil
+// elements, embedded non-struct types, and nested slices containing maps or
+// structs. (e.g. [][]map[string]string is not allowed but []map[string]string
+// is okay, as is []map[string][]string).
+//
+// NOTE: only exported keys are encoded due to the use of reflection. Unexported
+// keys are silently discarded.
+type Encoder struct {
+	Indent     string // string for a single indentation level; default is two spaces.
+	hasWritten bool   // written any output to w yet?
+	w          *bufio.Writer
+}
+
+// NewEncoder create a new Encoder.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{w: bufio.NewWriter(w), Indent: "  "}
+}
+
+// Encode writes a TOML representation of the Go value to the [Encoder]'s writer.
+//
+// An error is returned if the value given cannot be encoded to a valid TOML
+// document.
+func (enc *Encoder) Encode(v any) error {
+	rv := eindirect(reflect.ValueOf(v))
+	err := enc.safeEncode(Key([]string{}), rv)
+	if err != nil {
+		return err
+	}
+	return enc.w.Flush()
+}
+
+func (enc *Encoder) safeEncode(key Key, rv reflect.Value) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if terr, ok := r.(tomlEncodeError); ok {
+				err = terr.error
+				return
+			}
+			panic(r)
+		}
+	}()
+	enc.encode(key, rv)
+	return nil
+}
+
+func (enc *Encoder) encode(key Key, rv reflect.Value) {
+	// If we can marshal the type to text, then we use that. This prevents the
+	// encoder for handling these types as generic structs (or whatever the
+	// underlying type of a TextMarshaler is).
+	switch {
+	case isMarshaler(rv):
+		enc.writeKeyValue(key, rv, false)
+		return
+	case rv.Type() == primitiveType: // TODO: #76 would make this superfluous after implemented.
+		enc.encode(key, reflect.ValueOf(rv.Interface().(Primitive).undecoded))
+		return
+	}
+
+	k := rv.Kind()
+	switch k {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
+		reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
+		reflect.Uint64,
+		reflect.Float32, reflect.Float64, reflect.String, reflect.Bool:
+		enc.writeKeyValue(key, rv, false)
+	case reflect.Array, reflect.Slice:
+		if typeEqual(tomlArrayHash, tomlTypeOfGo(rv)) {
+			enc.eArrayOfTables(key, rv)
+		} else {
+			enc.writeKeyValue(key, rv, false)
+		}
+	case reflect.Interface:
+		if rv.IsNil() {
+			return
+		}
+		enc.encode(key, rv.Elem())
+	case reflect.Map:
+		if rv.IsNil() {
+			return
+		}
+		enc.eTable(key, rv)
+	case reflect.Ptr:
+		if rv.IsNil() {
+			return
+		}
+		enc.encode(key, rv.Elem())
+	case reflect.Struct:
+		enc.eTable(key, rv)
+	default:
+		encPanic(fmt.Errorf("unsupported type for key '%s': %s", key, k))
+	}
+}
+
+// eElement encodes any value that can be an array element.
+func (enc *Encoder) eElement(rv reflect.Value) {
+	switch v := rv.Interface().(type) {
+	case time.Time: // Using TextMarshaler adds extra quotes, which we don't want.
+		format := time.RFC3339Nano
+		switch v.Location() {
+		case internal.LocalDatetime:
+			format = "2006-01-02T15:04:05.999999999"
+		case internal.LocalDate:
+			format = "2006-01-02"
+		case internal.LocalTime:
+			format = "15:04:05.999999999"
+		}
+		switch v.Location() {
+		default:
+			enc.write(v.Format(format))
+		case internal.LocalDatetime, internal.LocalDate, internal.LocalTime:
+			enc.write(v.In(time.UTC).Format(format))
+		}
+		return
+	case Marshaler:
+		s, err := v.MarshalTOML()
+		if err != nil {
+			encPanic(err)
+		}
+		if s == nil {
+			encPanic(errors.New("MarshalTOML returned nil and no error"))
+		}
+		enc.w.Write(s)
+		return
+	case encoding.TextMarshaler:
+		s, err := v.MarshalText()
+		if err != nil {
+			encPanic(err)
+		}
+		if s == nil {
+			encPanic(errors.New("MarshalText returned nil and no error"))
+		}
+		enc.writeQuoted(string(s))
+		return
+	case time.Duration:
+		enc.writeQuoted(v.String())
+		return
+	case json.Number:
+		n, _ := rv.Interface().(json.Number)
+
+		if n == "" { /// Useful zero value.
+			enc.w.WriteByte('0')
+			return
+		} else if v, err := n.Int64(); err == nil {
+			enc.eElement(reflect.ValueOf(v))
+			return
+		} else if v, err := n.Float64(); err == nil {
+			enc.eElement(reflect.ValueOf(v))
+			return
+		}
+		encPanic(fmt.Errorf("unable to convert %q to int64 or float64", n))
+	}
+
+	switch rv.Kind() {
+	case reflect.Ptr:
+		enc.eElement(rv.Elem())
+		return
+	case reflect.String:
+		enc.writeQuoted(rv.String())
+	case reflect.Bool:
+		enc.write(strconv.FormatBool(rv.Bool()))
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		enc.write(strconv.FormatInt(rv.Int(), 10))
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		enc.write(strconv.FormatUint(rv.Uint(), 10))
+	case reflect.Float32:
+		f := rv.Float()
+		if math.IsNaN(f) {
+			if math.Signbit(f) {
+				enc.write("-")
+			}
+			enc.write("nan")
+		} else if math.IsInf(f, 0) {
+			if math.Signbit(f) {
+				enc.write("-")
+			}
+			enc.write("inf")
+		} else {
+			enc.write(floatAddDecimal(strconv.FormatFloat(f, 'g', -1, 32)))
+		}
+	case reflect.Float64:
+		f := rv.Float()
+		if math.IsNaN(f) {
+			if math.Signbit(f) {
+				enc.write("-")
+			}
+			enc.write("nan")
+		} else if math.IsInf(f, 0) {
+			if math.Signbit(f) {
+				enc.write("-")
+			}
+			enc.write("inf")
+		} else {
+			enc.write(floatAddDecimal(strconv.FormatFloat(f, 'g', -1, 64)))
+		}
+	case reflect.Array, reflect.Slice:
+		enc.eArrayOrSliceElement(rv)
+	case reflect.Struct:
+		enc.eStruct(nil, rv, true)
+	case reflect.Map:
+		enc.eMap(nil, rv, true)
+	case reflect.Interface:
+		enc.eElement(rv.Elem())
+	default:
+		encPanic(fmt.Errorf("unexpected type: %s", fmtType(rv.Interface())))
+	}
+}
+
+// By the TOML spec, all floats must have a decimal with at least one number on
+// either side.
+func floatAddDecimal(fstr string) string {
+	for _, c := range fstr {
+		if c == 'e' { // Exponent syntax
+			return fstr
+		}
+		if c == '.' {
+			return fstr
+		}
+	}
+	return fstr + ".0"
+}
+
+func (enc *Encoder) writeQuoted(s string) {
+	enc.write(`"` + dblQuotedReplacer.Replace(s) + `"`)
+}
+
+func (enc *Encoder) eArrayOrSliceElement(rv reflect.Value) {
+	length := rv.Len()
+	enc.write("[")
+	for i := 0; i < length; i++ {
+		elem := eindirect(rv.Index(i))
+		enc.eElement(elem)
+		if i != length-1 {
+			enc.write(", ")
+		}
+	}
+	enc.write("]")
+}
+
+func (enc *Encoder) eArrayOfTables(key Key, rv reflect.Value) {
+	if len(key) == 0 {
+		encPanic(errNoKey)
+	}
+	for i := 0; i < rv.Len(); i++ {
+		trv := eindirect(rv.Index(i))
+		if isNil(trv) {
+			continue
+		}
+		enc.newline()
+		enc.writef("%s[[%s]]", enc.indentStr(key), key)
+		enc.newline()
+		enc.eMapOrStruct(key, trv, false)
+	}
+}
+
+func (enc *Encoder) eTable(key Key, rv reflect.Value) {
+	if len(key) == 1 {
+		// Output an extra newline between top-level tables.
+		// (The newline isn't written if nothing else has been written though.)
+		enc.newline()
+	}
+	if len(key) > 0 {
+		enc.writef("%s[%s]", enc.indentStr(key), key)
+		enc.newline()
+	}
+	enc.eMapOrStruct(key, rv, false)
+}
+
+func (enc *Encoder) eMapOrStruct(key Key, rv reflect.Value, inline bool) {
+	switch rv.Kind() {
+	case reflect.Map:
+		enc.eMap(key, rv, inline)
+	case reflect.Struct:
+		enc.eStruct(key, rv, inline)
+	default:
+		// Should never happen?
+		panic("eTable: unhandled reflect.Value Kind: " + rv.Kind().String())
+	}
+}
+
+func (enc *Encoder) eMap(key Key, rv reflect.Value, inline bool) {
+	rt := rv.Type()
+	if rt.Key().Kind() != reflect.String {
+		encPanic(errNonString)
+	}
+
+	// Sort keys so that we have deterministic output. And write keys directly
+	// underneath this key first, before writing sub-structs or sub-maps.
+	var mapKeysDirect, mapKeysSub []reflect.Value
+	for _, mapKey := range rv.MapKeys() {
+		if typeIsTable(tomlTypeOfGo(eindirect(rv.MapIndex(mapKey)))) {
+			mapKeysSub = append(mapKeysSub, mapKey)
+		} else {
+			mapKeysDirect = append(mapKeysDirect, mapKey)
+		}
+	}
+
+	writeMapKeys := func(mapKeys []reflect.Value, trailC bool) {
+		sort.Slice(mapKeys, func(i, j int) bool { return mapKeys[i].String() < mapKeys[j].String() })
+		for i, mapKey := range mapKeys {
+			val := eindirect(rv.MapIndex(mapKey))
+			if isNil(val) {
+				continue
+			}
+
+			if inline {
+				enc.writeKeyValue(Key{mapKey.String()}, val, true)
+				if trailC || i != len(mapKeys)-1 {
+					enc.write(", ")
+				}
+			} else {
+				enc.encode(key.add(mapKey.String()), val)
+			}
+		}
+	}
+
+	if inline {
+		enc.write("{")
+	}
+	writeMapKeys(mapKeysDirect, len(mapKeysSub) > 0)
+	writeMapKeys(mapKeysSub, false)
+	if inline {
+		enc.write("}")
+	}
+}
+
+func pointerTo(t reflect.Type) reflect.Type {
+	if t.Kind() == reflect.Ptr {
+		return pointerTo(t.Elem())
+	}
+	return t
+}
+
+func (enc *Encoder) eStruct(key Key, rv reflect.Value, inline bool) {
+	// Write keys for fields directly under this key first, because if we write
+	// a field that creates a new table then all keys under it will be in that
+	// table (not the one we're writing here).
+	//
+	// Fields is a [][]int: for fieldsDirect this always has one entry (the
+	// struct index). For fieldsSub it contains two entries: the parent field
+	// index from tv, and the field indexes for the fields of the sub.
+	var (
+		rt                      = rv.Type()
+		fieldsDirect, fieldsSub [][]int
+		addFields               func(rt reflect.Type, rv reflect.Value, start []int)
+	)
+	addFields = func(rt reflect.Type, rv reflect.Value, start []int) {
+		for i := 0; i < rt.NumField(); i++ {
+			f := rt.Field(i)
+			isEmbed := f.Anonymous && pointerTo(f.Type).Kind() == reflect.Struct
+			if f.PkgPath != "" && !isEmbed { /// Skip unexported fields.
+				continue
+			}
+			opts := getOptions(f.Tag)
+			if opts.skip {
+				continue
+			}
+
+			frv := eindirect(rv.Field(i))
+
+			// Need to make a copy because ... ehm, I don't know why... I guess
+			// allocating a new array can cause it to fail(?)
+			//
+			// Done for: https://github.com/BurntSushi/toml/issues/430
+			// Previously only on 32bit for: https://github.com/BurntSushi/toml/issues/314
+			copyStart := make([]int, len(start))
+			copy(copyStart, start)
+			start = copyStart
+
+			// Treat anonymous struct fields with tag names as though they are
+			// not anonymous, like encoding/json does.
+			//
+			// Non-struct anonymous fields use the normal encoding logic.
+			if isEmbed {
+				if getOptions(f.Tag).name == "" && frv.Kind() == reflect.Struct {
+					addFields(frv.Type(), frv, append(start, f.Index...))
+					continue
+				}
+			}
+
+			if typeIsTable(tomlTypeOfGo(frv)) {
+				fieldsSub = append(fieldsSub, append(start, f.Index...))
+			} else {
+				fieldsDirect = append(fieldsDirect, append(start, f.Index...))
+			}
+		}
+	}
+	addFields(rt, rv, nil)
+
+	writeFields := func(fields [][]int, totalFields int) {
+		for _, fieldIndex := range fields {
+			fieldType := rt.FieldByIndex(fieldIndex)
+			fieldVal := rv.FieldByIndex(fieldIndex)
+
+			opts := getOptions(fieldType.Tag)
+			if opts.skip {
+				continue
+			}
+			if opts.omitempty && isEmpty(fieldVal) {
+				continue
+			}
+
+			fieldVal = eindirect(fieldVal)
+
+			if isNil(fieldVal) { /// Don't write anything for nil fields.
+				continue
+			}
+
+			keyName := fieldType.Name
+			if opts.name != "" {
+				keyName = opts.name
+			}
+
+			if opts.omitzero && isZero(fieldVal) {
+				continue
+			}
+
+			if inline {
+				enc.writeKeyValue(Key{keyName}, fieldVal, true)
+				if fieldIndex[0] != totalFields-1 {
+					enc.write(", ")
+				}
+			} else {
+				enc.encode(key.add(keyName), fieldVal)
+			}
+		}
+	}
+
+	if inline {
+		enc.write("{")
+	}
+
+	l := len(fieldsDirect) + len(fieldsSub)
+	writeFields(fieldsDirect, l)
+	writeFields(fieldsSub, l)
+	if inline {
+		enc.write("}")
+	}
+}
+
+// tomlTypeOfGo returns the TOML type name of the Go value's type.
+//
+// It is used to determine whether the types of array elements are mixed (which
+// is forbidden). If the Go value is nil, then it is illegal for it to be an
+// array element, and valueIsNil is returned as true.
+//
+// The type may be `nil`, which means no concrete TOML type could be found.
+func tomlTypeOfGo(rv reflect.Value) tomlType {
+	if isNil(rv) || !rv.IsValid() {
+		return nil
+	}
+
+	if rv.Kind() == reflect.Struct {
+		if rv.Type() == timeType {
+			return tomlDatetime
+		}
+		if isMarshaler(rv) {
+			return tomlString
+		}
+		return tomlHash
+	}
+
+	if isMarshaler(rv) {
+		return tomlString
+	}
+
+	switch rv.Kind() {
+	case reflect.Bool:
+		return tomlBool
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
+		reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
+		reflect.Uint64:
+		return tomlInteger
+	case reflect.Float32, reflect.Float64:
+		return tomlFloat
+	case reflect.Array, reflect.Slice:
+		if isTableArray(rv) {
+			return tomlArrayHash
+		}
+		return tomlArray
+	case reflect.Ptr, reflect.Interface:
+		return tomlTypeOfGo(rv.Elem())
+	case reflect.String:
+		return tomlString
+	case reflect.Map:
+		return tomlHash
+	default:
+		encPanic(errors.New("unsupported type: " + rv.Kind().String()))
+		panic("unreachable")
+	}
+}
+
+func isMarshaler(rv reflect.Value) bool {
+	return rv.Type().Implements(marshalText) || rv.Type().Implements(marshalToml)
+}
+
+// isTableArray reports if all entries in the array or slice are a table.
+func isTableArray(arr reflect.Value) bool {
+	if isNil(arr) || !arr.IsValid() || arr.Len() == 0 {
+		return false
+	}
+
+	ret := true
+	for i := 0; i < arr.Len(); i++ {
+		tt := tomlTypeOfGo(eindirect(arr.Index(i)))
+		// Don't allow nil.
+		if tt == nil {
+			encPanic(errArrayNilElement)
+		}
+
+		if ret && !typeEqual(tomlHash, tt) {
+			ret = false
+		}
+	}
+	return ret
+}
+
+type tagOptions struct {
+	skip      bool // "-"
+	name      string
+	omitempty bool
+	omitzero  bool
+}
+
+func getOptions(tag reflect.StructTag) tagOptions {
+	t := tag.Get("toml")
+	if t == "-" {
+		return tagOptions{skip: true}
+	}
+	var opts tagOptions
+	parts := strings.Split(t, ",")
+	opts.name = parts[0]
+	for _, s := range parts[1:] {
+		switch s {
+		case "omitempty":
+			opts.omitempty = true
+		case "omitzero":
+			opts.omitzero = true
+		}
+	}
+	return opts
+}
+
+func isZero(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return rv.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return rv.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return rv.Float() == 0.0
+	}
+	return false
+}
+
+func isEmpty(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Array, reflect.Slice, reflect.Map, reflect.String:
+		return rv.Len() == 0
+	case reflect.Struct:
+		if rv.Type().Comparable() {
+			return reflect.Zero(rv.Type()).Interface() == rv.Interface()
+		}
+		// Need to also check if all the fields are empty, otherwise something
+		// like this with uncomparable types will always return true:
+		//
+		//   type a struct{ field b }
+		//   type b struct{ s []string }
+		//   s := a{field: b{s: []string{"AAA"}}}
+		for i := 0; i < rv.NumField(); i++ {
+			if !isEmpty(rv.Field(i)) {
+				return false
+			}
+		}
+		return true
+	case reflect.Bool:
+		return !rv.Bool()
+	case reflect.Ptr:
+		return rv.IsNil()
+	}
+	return false
+}
+
+func (enc *Encoder) newline() {
+	if enc.hasWritten {
+		enc.write("\n")
+	}
+}
+
+// Write a key/value pair:
+//
+//	key = <any value>
+//
+// This is also used for "k = v" in inline tables; so something like this will
+// be written in three calls:
+//
+//	┌───────────────────┐
+//	│      ┌───┐  ┌────┐│
+//	v      v   v  v    vv
+//	key = {k = 1, k2 = 2}
+func (enc *Encoder) writeKeyValue(key Key, val reflect.Value, inline bool) {
+	/// Marshaler used on top-level document; call eElement() to just call
+	/// Marshal{TOML,Text}.
+	if len(key) == 0 {
+		enc.eElement(val)
+		return
+	}
+	enc.writef("%s%s = ", enc.indentStr(key), key.maybeQuoted(len(key)-1))
+	enc.eElement(val)
+	if !inline {
+		enc.newline()
+	}
+}
+
+func (enc *Encoder) write(s string) {
+	_, err := enc.w.WriteString(s)
+	if err != nil {
+		encPanic(err)
+	}
+	enc.hasWritten = true
+}
+
+func (enc *Encoder) writef(format string, v ...any) {
+	_, err := fmt.Fprintf(enc.w, format, v...)
+	if err != nil {
+		encPanic(err)
+	}
+	enc.hasWritten = true
+}
+
+func (enc *Encoder) indentStr(key Key) string {
+	return strings.Repeat(enc.Indent, len(key)-1)
+}
+
+func encPanic(err error) {
+	panic(tomlEncodeError{err})
+}
+
+// Resolve any level of pointers to the actual value (e.g. **string → string).
+func eindirect(v reflect.Value) reflect.Value {
+	if v.Kind() != reflect.Ptr && v.Kind() != reflect.Interface {
+		if isMarshaler(v) {
+			return v
+		}
+		if v.CanAddr() { /// Special case for marshalers; see #358.
+			if pv := v.Addr(); isMarshaler(pv) {
+				return pv
+			}
+		}
+		return v
+	}
+
+	if v.IsNil() {
+		return v
+	}
+
+	return eindirect(v.Elem())
+}
+
+func isNil(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
+		return rv.IsNil()
+	default:
+		return false
+	}
+}
@@ -0,0 +1,347 @@
+package toml
+
+import (
+	"fmt"
+	"strings"
+)
+
+// ParseError is returned when there is an error parsing the TOML syntax such as
+// invalid syntax, duplicate keys, etc.
+//
+// In addition to the error message itself, you can also print detailed location
+// information with context by using [ErrorWithPosition]:
+//
+//	toml: error: Key 'fruit' was already created and cannot be used as an array.
+//
+//	At line 4, column 2-7:
+//
+//	      2 | fruit = []
+//	      3 |
+//	      4 | [[fruit]] # Not allowed
+//	            ^^^^^
+//
+// [ErrorWithUsage] can be used to print the above with some more detailed usage
+// guidance:
+//
+//	toml: error: newlines not allowed within inline tables
+//
+//	At line 1, column 18:
+//
+//	      1 | x = [{ key = 42 #
+//	                           ^
+//
+//	Error help:
+//
+//	  Inline tables must always be on a single line:
+//
+//	      table = {key = 42, second = 43}
+//
+//	  It is invalid to split them over multiple lines like so:
+//
+//	      # INVALID
+//	      table = {
+//	          key    = 42,
+//	          second = 43
+//	      }
+//
+//	  Use regular for this:
+//
+//	      [table]
+//	      key    = 42
+//	      second = 43
+type ParseError struct {
+	Message  string   // Short technical message.
+	Usage    string   // Longer message with usage guidance; may be blank.
+	Position Position // Position of the error
+	LastKey  string   // Last parsed key, may be blank.
+
+	// Line the error occurred.
+	//
+	// Deprecated: use [Position].
+	Line int
+
+	err   error
+	input string
+}
+
+// Position of an error.
+type Position struct {
+	Line  int // Line number, starting at 1.
+	Col   int // Error column, starting at 1.
+	Start int // Start of error, as byte offset starting at 0.
+	Len   int // Length of the error in bytes.
+}
+
+func (p Position) withCol(tomlFile string) Position {
+	var (
+		pos   int
+		lines = strings.Split(tomlFile, "\n")
+	)
+	for i := range lines {
+		ll := len(lines[i]) + 1 // +1 for the removed newline
+		if pos+ll >= p.Start {
+			p.Col = p.Start - pos + 1
+			if p.Col < 1 { // Should never happen, but just in case.
+				p.Col = 1
+			}
+			break
+		}
+		pos += ll
+	}
+	return p
+}
+
+func (pe ParseError) Error() string {
+	if pe.LastKey == "" {
+		return fmt.Sprintf("toml: line %d: %s", pe.Position.Line, pe.Message)
+	}
+	return fmt.Sprintf("toml: line %d (last key %q): %s",
+		pe.Position.Line, pe.LastKey, pe.Message)
+}
+
+// ErrorWithPosition returns the error with detailed location context.
+//
+// See the documentation on [ParseError].
+func (pe ParseError) ErrorWithPosition() string {
+	if pe.input == "" { // Should never happen, but just in case.
+		return pe.Error()
+	}
+
+	// TODO: don't show control characters as literals? This may not show up
+	// well everywhere.
+
+	var (
+		lines = strings.Split(pe.input, "\n")
+		b     = new(strings.Builder)
+	)
+	if pe.Position.Len == 1 {
+		fmt.Fprintf(b, "toml: error: %s\n\nAt line %d, column %d:\n\n",
+			pe.Message, pe.Position.Line, pe.Position.Col)
+	} else {
+		fmt.Fprintf(b, "toml: error: %s\n\nAt line %d, column %d-%d:\n\n",
+			pe.Message, pe.Position.Line, pe.Position.Col, pe.Position.Col+pe.Position.Len-1)
+	}
+	if pe.Position.Line > 2 {
+		fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line-2, expandTab(lines[pe.Position.Line-3]))
+	}
+	if pe.Position.Line > 1 {
+		fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line-1, expandTab(lines[pe.Position.Line-2]))
+	}
+
+	/// Expand tabs, so that the ^^^s are at the correct position, but leave
+	/// "column 10-13" intact. Adjusting this to the visual column would be
+	/// better, but we don't know the tabsize of the user in their editor, which
+	/// can be 8, 4, 2, or something else. We can't know. So leaving it as the
+	/// character index is probably the "most correct".
+	expanded := expandTab(lines[pe.Position.Line-1])
+	diff := len(expanded) - len(lines[pe.Position.Line-1])
+
+	fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line, expanded)
+	fmt.Fprintf(b, "% 10s%s%s\n", "", strings.Repeat(" ", pe.Position.Col-1+diff), strings.Repeat("^", pe.Position.Len))
+	return b.String()
+}
+
+// ErrorWithUsage returns the error with detailed location context and usage
+// guidance.
+//
+// See the documentation on [ParseError].
+func (pe ParseError) ErrorWithUsage() string {
+	m := pe.ErrorWithPosition()
+	if u, ok := pe.err.(interface{ Usage() string }); ok && u.Usage() != "" {
+		lines := strings.Split(strings.TrimSpace(u.Usage()), "\n")
+		for i := range lines {
+			if lines[i] != "" {
+				lines[i] = "    " + lines[i]
+			}
+		}
+		return m + "Error help:\n\n" + strings.Join(lines, "\n") + "\n"
+	}
+	return m
+}
+
+func expandTab(s string) string {
+	var (
+		b    strings.Builder
+		l    int
+		fill = func(n int) string {
+			b := make([]byte, n)
+			for i := range b {
+				b[i] = ' '
+			}
+			return string(b)
+		}
+	)
+	b.Grow(len(s))
+	for _, r := range s {
+		switch r {
+		case '\t':
+			tw := 8 - l%8
+			b.WriteString(fill(tw))
+			l += tw
+		default:
+			b.WriteRune(r)
+			l += 1
+		}
+	}
+	return b.String()
+}
+
+type (
+	errLexControl       struct{ r rune }
+	errLexEscape        struct{ r rune }
+	errLexUTF8          struct{ b byte }
+	errParseDate        struct{ v string }
+	errLexInlineTableNL struct{}
+	errLexStringNL      struct{}
+	errParseRange       struct {
+		i    any    // int or float
+		size string // "int64", "uint16", etc.
+	}
+	errUnsafeFloat struct {
+		i    interface{} // float32 or float64
+		size string      // "float32" or "float64"
+	}
+	errParseDuration struct{ d string }
+)
+
+func (e errLexControl) Error() string {
+	return fmt.Sprintf("TOML files cannot contain control characters: '0x%02x'", e.r)
+}
+func (e errLexControl) Usage() string { return "" }
+
+func (e errLexEscape) Error() string        { return fmt.Sprintf(`invalid escape in string '\%c'`, e.r) }
+func (e errLexEscape) Usage() string        { return usageEscape }
+func (e errLexUTF8) Error() string          { return fmt.Sprintf("invalid UTF-8 byte: 0x%02x", e.b) }
+func (e errLexUTF8) Usage() string          { return "" }
+func (e errParseDate) Error() string        { return fmt.Sprintf("invalid datetime: %q", e.v) }
+func (e errParseDate) Usage() string        { return usageDate }
+func (e errLexInlineTableNL) Error() string { return "newlines not allowed within inline tables" }
+func (e errLexInlineTableNL) Usage() string { return usageInlineNewline }
+func (e errLexStringNL) Error() string      { return "strings cannot contain newlines" }
+func (e errLexStringNL) Usage() string      { return usageStringNewline }
+func (e errParseRange) Error() string       { return fmt.Sprintf("%v is out of range for %s", e.i, e.size) }
+func (e errParseRange) Usage() string       { return usageIntOverflow }
+func (e errUnsafeFloat) Error() string {
+	return fmt.Sprintf("%v is out of the safe %s range", e.i, e.size)
+}
+func (e errUnsafeFloat) Usage() string   { return usageUnsafeFloat }
+func (e errParseDuration) Error() string { return fmt.Sprintf("invalid duration: %q", e.d) }
+func (e errParseDuration) Usage() string { return usageDuration }
+
+const usageEscape = `
+A '\' inside a "-delimited string is interpreted as an escape character.
+
+The following escape sequences are supported:
+\b, \t, \n, \f, \r, \", \\, \uXXXX, and \UXXXXXXXX
+
+To prevent a '\' from being recognized as an escape character, use either:
+
+- a ' or '''-delimited string; escape characters aren't processed in them; or
+- write two backslashes to get a single backslash: '\\'.
+
+If you're trying to add a Windows path (e.g. "C:\Users\martin") then using '/'
+instead of '\' will usually also work: "C:/Users/martin".
+`
+
+const usageInlineNewline = `
+Inline tables must always be on a single line:
+
+    table = {key = 42, second = 43}
+
+It is invalid to split them over multiple lines like so:
+
+    # INVALID
+    table = {
+        key    = 42,
+        second = 43
+    }
+
+Use regular for this:
+
+    [table]
+    key    = 42
+    second = 43
+`
+
+const usageStringNewline = `
+Strings must always be on a single line, and cannot span more than one line:
+
+    # INVALID
+    string = "Hello,
+    world!"
+
+Instead use """ or ''' to split strings over multiple lines:
+
+    string = """Hello,
+    world!"""
+`
+
+const usageIntOverflow = `
+This number is too large; this may be an error in the TOML, but it can also be a
+bug in the program that uses too small of an integer.
+
+The maximum and minimum values are:
+
+    size   │ lowest         │ highest
+    ───────┼────────────────┼──────────────
+    int8   │ -128           │ 127
+    int16  │ -32,768        │ 32,767
+    int32  │ -2,147,483,648 │ 2,147,483,647
+    int64  │ -9.2 × 10¹⁷    │ 9.2 × 10¹⁷
+    uint8  │ 0              │ 255
+    uint16 │ 0              │ 65,535
+    uint32 │ 0              │ 4,294,967,295
+    uint64 │ 0              │ 1.8 × 10¹⁸
+
+int refers to int32 on 32-bit systems and int64 on 64-bit systems.
+`
+
+const usageUnsafeFloat = `
+This number is outside of the "safe" range for floating point numbers; whole
+(non-fractional) numbers outside the below range can not always be represented
+accurately in a float, leading to some loss of accuracy.
+
+Explicitly mark a number as a fractional unit by adding ".0", which will incur
+some loss of accuracy; for example:
+
+	f = 2_000_000_000.0
+
+Accuracy ranges:
+
+	float32 =            16,777,215
+	float64 = 9,007,199,254,740,991
+`
+
+const usageDuration = `
+A duration must be as "number<unit>", without any spaces. Valid units are:
+
+    ns         nanoseconds (billionth of a second)
+    us, µs     microseconds (millionth of a second)
+    ms         milliseconds (thousands of a second)
+    s          seconds
+    m          minutes
+    h          hours
+
+You can combine multiple units; for example "5m10s" for 5 minutes and 10
+seconds.
+`
+
+const usageDate = `
+A TOML datetime must be in one of the following formats:
+
+    2006-01-02T15:04:05Z07:00   Date and time, with timezone.
+    2006-01-02T15:04:05         Date and time, but without timezone.
+    2006-01-02                  Date without a time or timezone.
+    15:04:05                    Just a time, without any timezone.
+
+Seconds may optionally have a fraction, up to nanosecond precision:
+
+    15:04:05.123
+    15:04:05.856018510
+`
+
+// TOML 1.1:
+// The seconds part in times is optional, and may be omitted:
+//     2006-01-02T15:04Z07:00
+//     2006-01-02T15:04
+//     15:04
@@ -0,0 +1,36 @@
+package internal
+
+import "time"
+
+// Timezones used for local datetime, date, and time TOML types.
+//
+// The exact way times and dates without a timezone should be interpreted is not
+// well-defined in the TOML specification and left to the implementation. These
+// defaults to current local timezone offset of the computer, but this can be
+// changed by changing these variables before decoding.
+//
+// TODO:
+// Ideally we'd like to offer people the ability to configure the used timezone
+// by setting Decoder.Timezone and Encoder.Timezone; however, this is a bit
+// tricky: the reason we use three different variables for this is to support
+// round-tripping – without these specific TZ names we wouldn't know which
+// format to use.
+//
+// There isn't a good way to encode this right now though, and passing this sort
+// of information also ties in to various related issues such as string format
+// encoding, encoding of comments, etc.
+//
+// So, for the time being, just put this in internal until we can write a good
+// comprehensive API for doing all of this.
+//
+// The reason they're exported is because they're referred from in e.g.
+// internal/tag.
+//
+// Note that this behaviour is valid according to the TOML spec as the exact
+// behaviour is left up to implementations.
+var (
+	localOffset   = func() int { _, o := time.Now().Zone(); return o }()
+	LocalDatetime = time.FixedZone("datetime-local", localOffset)
+	LocalDate     = time.FixedZone("date-local", localOffset)
+	LocalTime     = time.FixedZone("time-local", localOffset)
+)
@@ -0,0 +1,145 @@
+package toml
+
+import (
+	"strings"
+)
+
+// MetaData allows access to meta information about TOML data that's not
+// accessible otherwise.
+//
+// It allows checking if a key is defined in the TOML data, whether any keys
+// were undecoded, and the TOML type of a key.
+type MetaData struct {
+	context Key // Used only during decoding.
+
+	keyInfo map[string]keyInfo
+	mapping map[string]any
+	keys    []Key
+	decoded map[string]struct{}
+	data    []byte // Input file; for errors.
+}
+
+// IsDefined reports if the key exists in the TOML data.
+//
+// The key should be specified hierarchically, for example to access the TOML
+// key "a.b.c" you would use IsDefined("a", "b", "c"). Keys are case sensitive.
+//
+// Returns false for an empty key.
+func (md *MetaData) IsDefined(key ...string) bool {
+	if len(key) == 0 {
+		return false
+	}
+
+	var (
+		hash      map[string]any
+		ok        bool
+		hashOrVal any = md.mapping
+	)
+	for _, k := range key {
+		if hash, ok = hashOrVal.(map[string]any); !ok {
+			return false
+		}
+		if hashOrVal, ok = hash[k]; !ok {
+			return false
+		}
+	}
+	return true
+}
+
+// Type returns a string representation of the type of the key specified.
+//
+// Type will return the empty string if given an empty key or a key that does
+// not exist. Keys are case sensitive.
+func (md *MetaData) Type(key ...string) string {
+	if ki, ok := md.keyInfo[Key(key).String()]; ok {
+		return ki.tomlType.typeString()
+	}
+	return ""
+}
+
+// Keys returns a slice of every key in the TOML data, including key groups.
+//
+// Each key is itself a slice, where the first element is the top of the
+// hierarchy and the last is the most specific. The list will have the same
+// order as the keys appeared in the TOML data.
+//
+// All keys returned are non-empty.
+func (md *MetaData) Keys() []Key {
+	return md.keys
+}
+
+// Undecoded returns all keys that have not been decoded in the order in which
+// they appear in the original TOML document.
+//
+// This includes keys that haven't been decoded because of a [Primitive] value.
+// Once the Primitive value is decoded, the keys will be considered decoded.
+//
+// Also note that decoding into an empty interface will result in no decoding,
+// and so no keys will be considered decoded.
+//
+// In this sense, the Undecoded keys correspond to keys in the TOML document
+// that do not have a concrete type in your representation.
+func (md *MetaData) Undecoded() []Key {
+	undecoded := make([]Key, 0, len(md.keys))
+	for _, key := range md.keys {
+		if _, ok := md.decoded[key.String()]; !ok {
+			undecoded = append(undecoded, key)
+		}
+	}
+	return undecoded
+}
+
+// Key represents any TOML key, including key groups. Use [MetaData.Keys] to get
+// values of this type.
+type Key []string
+
+func (k Key) String() string {
+	// This is called quite often, so it's a bit funky to make it faster.
+	var b strings.Builder
+	b.Grow(len(k) * 25)
+outer:
+	for i, kk := range k {
+		if i > 0 {
+			b.WriteByte('.')
+		}
+		if kk == "" {
+			b.WriteString(`""`)
+		} else {
+			for _, r := range kk {
+				// "Inline" isBareKeyChar
+				if !((r >= 'A' && r <= 'Z') || (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '_' || r == '-') {
+					b.WriteByte('"')
+					b.WriteString(dblQuotedReplacer.Replace(kk))
+					b.WriteByte('"')
+					continue outer
+				}
+			}
+			b.WriteString(kk)
+		}
+	}
+	return b.String()
+}
+
+func (k Key) maybeQuoted(i int) string {
+	if k[i] == "" {
+		return `""`
+	}
+	for _, r := range k[i] {
+		if (r >= 'A' && r <= 'Z') || (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '_' || r == '-' {
+			continue
+		}
+		return `"` + dblQuotedReplacer.Replace(k[i]) + `"`
+	}
+	return k[i]
+}
+
+// Like append(), but only increase the cap by 1.
+func (k Key) add(piece string) Key {
+	newKey := make(Key, len(k)+1)
+	copy(newKey, k)
+	newKey[len(k)] = piece
+	return newKey
+}
+
+func (k Key) parent() Key  { return k[:len(k)-1] } // all except the last piece.
+func (k Key) last() string { return k[len(k)-1] }  // last piece of this key.
@@ -0,0 +1,835 @@
+package toml
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/BurntSushi/toml/internal"
+)
+
+type parser struct {
+	lx         *lexer
+	context    Key      // Full key for the current hash in scope.
+	currentKey string   // Base key name for everything except hashes.
+	pos        Position // Current position in the TOML file.
+
+	ordered []Key // List of keys in the order that they appear in the TOML data.
+
+	keyInfo   map[string]keyInfo  // Map keyname → info about the TOML key.
+	mapping   map[string]any      // Map keyname → key value.
+	implicits map[string]struct{} // Record implicit keys (e.g. "key.group.names").
+}
+
+type keyInfo struct {
+	pos      Position
+	tomlType tomlType
+}
+
+func parse(data string) (p *parser, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if pErr, ok := r.(ParseError); ok {
+				pErr.input = data
+				err = pErr
+				return
+			}
+			panic(r)
+		}
+	}()
+
+	// Read over BOM; do this here as the lexer calls utf8.DecodeRuneInString()
+	// which mangles stuff. UTF-16 BOM isn't strictly valid, but some tools add
+	// it anyway.
+	if strings.HasPrefix(data, "\xff\xfe") || strings.HasPrefix(data, "\xfe\xff") { // UTF-16
+		data = data[2:]
+	} else if strings.HasPrefix(data, "\xef\xbb\xbf") { // UTF-8
+		data = data[3:]
+	}
+
+	// Examine first few bytes for NULL bytes; this probably means it's a UTF-16
+	// file (second byte in surrogate pair being NULL). Again, do this here to
+	// avoid having to deal with UTF-8/16 stuff in the lexer.
+	ex := 6
+	if len(data) < 6 {
+		ex = len(data)
+	}
+	if i := strings.IndexRune(data[:ex], 0); i > -1 {
+		return nil, ParseError{
+			Message:  "files cannot contain NULL bytes; probably using UTF-16; TOML files must be UTF-8",
+			Position: Position{Line: 1, Col: 1, Start: i, Len: 1},
+			Line:     1,
+			input:    data,
+		}
+	}
+
+	p = &parser{
+		keyInfo:   make(map[string]keyInfo),
+		mapping:   make(map[string]any),
+		lx:        lex(data),
+		ordered:   make([]Key, 0),
+		implicits: make(map[string]struct{}),
+	}
+	for {
+		item := p.next()
+		if item.typ == itemEOF {
+			break
+		}
+		p.topLevel(item)
+	}
+
+	return p, nil
+}
+
+func (p *parser) panicErr(it item, err error) {
+	panic(ParseError{
+		Message:  err.Error(),
+		err:      err,
+		Position: it.pos.withCol(p.lx.input),
+		Line:     it.pos.Len,
+		LastKey:  p.current(),
+	})
+}
+
+func (p *parser) panicItemf(it item, format string, v ...any) {
+	panic(ParseError{
+		Message:  fmt.Sprintf(format, v...),
+		Position: it.pos.withCol(p.lx.input),
+		Line:     it.pos.Len,
+		LastKey:  p.current(),
+	})
+}
+
+func (p *parser) panicf(format string, v ...any) {
+	panic(ParseError{
+		Message:  fmt.Sprintf(format, v...),
+		Position: p.pos.withCol(p.lx.input),
+		Line:     p.pos.Line,
+		LastKey:  p.current(),
+	})
+}
+
+func (p *parser) next() item {
+	it := p.lx.nextItem()
+	//fmt.Printf("ITEM %-18s line %-3d │ %q\n", it.typ, it.pos.Line, it.val)
+	if it.typ == itemError {
+		if it.err != nil {
+			panic(ParseError{
+				Message:  it.err.Error(),
+				err:      it.err,
+				Position: it.pos.withCol(p.lx.input),
+				Line:     it.pos.Line,
+				LastKey:  p.current(),
+			})
+		}
+
+		p.panicItemf(it, "%s", it.val)
+	}
+	return it
+}
+
+func (p *parser) nextPos() item {
+	it := p.next()
+	p.pos = it.pos
+	return it
+}
+
+func (p *parser) bug(format string, v ...any) {
+	panic(fmt.Sprintf("BUG: "+format+"\n\n", v...))
+}
+
+func (p *parser) expect(typ itemType) item {
+	it := p.next()
+	p.assertEqual(typ, it.typ)
+	return it
+}
+
+func (p *parser) assertEqual(expected, got itemType) {
+	if expected != got {
+		p.bug("Expected '%s' but got '%s'.", expected, got)
+	}
+}
+
+func (p *parser) topLevel(item item) {
+	switch item.typ {
+	case itemCommentStart: // # ..
+		p.expect(itemText)
+	case itemTableStart: // [ .. ]
+		name := p.nextPos()
+
+		var key Key
+		for ; name.typ != itemTableEnd && name.typ != itemEOF; name = p.next() {
+			key = append(key, p.keyString(name))
+		}
+		p.assertEqual(itemTableEnd, name.typ)
+
+		p.addContext(key, false)
+		p.setType("", tomlHash, item.pos)
+		p.ordered = append(p.ordered, key)
+	case itemArrayTableStart: // [[ .. ]]
+		name := p.nextPos()
+
+		var key Key
+		for ; name.typ != itemArrayTableEnd && name.typ != itemEOF; name = p.next() {
+			key = append(key, p.keyString(name))
+		}
+		p.assertEqual(itemArrayTableEnd, name.typ)
+
+		p.addContext(key, true)
+		p.setType("", tomlArrayHash, item.pos)
+		p.ordered = append(p.ordered, key)
+	case itemKeyStart: // key = ..
+		outerContext := p.context
+		/// Read all the key parts (e.g. 'a' and 'b' in 'a.b')
+		k := p.nextPos()
+		var key Key
+		for ; k.typ != itemKeyEnd && k.typ != itemEOF; k = p.next() {
+			key = append(key, p.keyString(k))
+		}
+		p.assertEqual(itemKeyEnd, k.typ)
+
+		/// The current key is the last part.
+		p.currentKey = key.last()
+
+		/// All the other parts (if any) are the context; need to set each part
+		/// as implicit.
+		context := key.parent()
+		for i := range context {
+			p.addImplicitContext(append(p.context, context[i:i+1]...))
+		}
+		p.ordered = append(p.ordered, p.context.add(p.currentKey))
+
+		/// Set value.
+		vItem := p.next()
+		val, typ := p.value(vItem, false)
+		p.setValue(p.currentKey, val)
+		p.setType(p.currentKey, typ, vItem.pos)
+
+		/// Remove the context we added (preserving any context from [tbl] lines).
+		p.context = outerContext
+		p.currentKey = ""
+	default:
+		p.bug("Unexpected type at top level: %s", item.typ)
+	}
+}
+
+// Gets a string for a key (or part of a key in a table name).
+func (p *parser) keyString(it item) string {
+	switch it.typ {
+	case itemText:
+		return it.val
+	case itemString, itemStringEsc, itemMultilineString,
+		itemRawString, itemRawMultilineString:
+		s, _ := p.value(it, false)
+		return s.(string)
+	default:
+		p.bug("Unexpected key type: %s", it.typ)
+	}
+	panic("unreachable")
+}
+
+var datetimeRepl = strings.NewReplacer(
+	"z", "Z",
+	"t", "T",
+	" ", "T")
+
+// value translates an expected value from the lexer into a Go value wrapped
+// as an empty interface.
+func (p *parser) value(it item, parentIsArray bool) (any, tomlType) {
+	switch it.typ {
+	case itemString:
+		return it.val, p.typeOfPrimitive(it)
+	case itemStringEsc:
+		return p.replaceEscapes(it, it.val), p.typeOfPrimitive(it)
+	case itemMultilineString:
+		return p.replaceEscapes(it, p.stripEscapedNewlines(stripFirstNewline(it.val))), p.typeOfPrimitive(it)
+	case itemRawString:
+		return it.val, p.typeOfPrimitive(it)
+	case itemRawMultilineString:
+		return stripFirstNewline(it.val), p.typeOfPrimitive(it)
+	case itemInteger:
+		return p.valueInteger(it)
+	case itemFloat:
+		return p.valueFloat(it)
+	case itemBool:
+		switch it.val {
+		case "true":
+			return true, p.typeOfPrimitive(it)
+		case "false":
+			return false, p.typeOfPrimitive(it)
+		default:
+			p.bug("Expected boolean value, but got '%s'.", it.val)
+		}
+	case itemDatetime:
+		return p.valueDatetime(it)
+	case itemArray:
+		return p.valueArray(it)
+	case itemInlineTableStart:
+		return p.valueInlineTable(it, parentIsArray)
+	default:
+		p.bug("Unexpected value type: %s", it.typ)
+	}
+	panic("unreachable")
+}
+
+func (p *parser) valueInteger(it item) (any, tomlType) {
+	if !numUnderscoresOK(it.val) {
+		p.panicItemf(it, "Invalid integer %q: underscores must be surrounded by digits", it.val)
+	}
+	if numHasLeadingZero(it.val) {
+		p.panicItemf(it, "Invalid integer %q: cannot have leading zeroes", it.val)
+	}
+
+	num, err := strconv.ParseInt(it.val, 0, 64)
+	if err != nil {
+		// Distinguish integer values. Normally, it'd be a bug if the lexer
+		// provides an invalid integer, but it's possible that the number is
+		// out of range of valid values (which the lexer cannot determine).
+		// So mark the former as a bug but the latter as a legitimate user
+		// error.
+		if e, ok := err.(*strconv.NumError); ok && e.Err == strconv.ErrRange {
+			p.panicErr(it, errParseRange{i: it.val, size: "int64"})
+		} else {
+			p.bug("Expected integer value, but got '%s'.", it.val)
+		}
+	}
+	return num, p.typeOfPrimitive(it)
+}
+
+func (p *parser) valueFloat(it item) (any, tomlType) {
+	parts := strings.FieldsFunc(it.val, func(r rune) bool {
+		switch r {
+		case '.', 'e', 'E':
+			return true
+		}
+		return false
+	})
+	for _, part := range parts {
+		if !numUnderscoresOK(part) {
+			p.panicItemf(it, "Invalid float %q: underscores must be surrounded by digits", it.val)
+		}
+	}
+	if len(parts) > 0 && numHasLeadingZero(parts[0]) {
+		p.panicItemf(it, "Invalid float %q: cannot have leading zeroes", it.val)
+	}
+	if !numPeriodsOK(it.val) {
+		// As a special case, numbers like '123.' or '1.e2',
+		// which are valid as far as Go/strconv are concerned,
+		// must be rejected because TOML says that a fractional
+		// part consists of '.' followed by 1+ digits.
+		p.panicItemf(it, "Invalid float %q: '.' must be followed by one or more digits", it.val)
+	}
+	val := strings.Replace(it.val, "_", "", -1)
+	signbit := false
+	if val == "+nan" || val == "-nan" {
+		signbit = val == "-nan"
+		val = "nan"
+	}
+	num, err := strconv.ParseFloat(val, 64)
+	if err != nil {
+		if e, ok := err.(*strconv.NumError); ok && e.Err == strconv.ErrRange {
+			p.panicErr(it, errParseRange{i: it.val, size: "float64"})
+		} else {
+			p.panicItemf(it, "Invalid float value: %q", it.val)
+		}
+	}
+	if signbit {
+		num = math.Copysign(num, -1)
+	}
+	return num, p.typeOfPrimitive(it)
+}
+
+var dtTypes = []struct {
+	fmt  string
+	zone *time.Location
+}{
+	{time.RFC3339Nano, time.Local},
+	{"2006-01-02T15:04:05.999999999", internal.LocalDatetime},
+	{"2006-01-02", internal.LocalDate},
+	{"15:04:05.999999999", internal.LocalTime},
+	{"2006-01-02T15:04Z07:00", time.Local},
+	{"2006-01-02T15:04", internal.LocalDatetime},
+	{"15:04", internal.LocalTime},
+}
+
+func (p *parser) valueDatetime(it item) (any, tomlType) {
+	it.val = datetimeRepl.Replace(it.val)
+	var (
+		t   time.Time
+		ok  bool
+		err error
+	)
+	for _, dt := range dtTypes {
+		t, err = time.ParseInLocation(dt.fmt, it.val, dt.zone)
+		if err == nil {
+			if missingLeadingZero(it.val, dt.fmt) {
+				p.panicErr(it, errParseDate{it.val})
+			}
+			ok = true
+			break
+		}
+	}
+	if !ok {
+		p.panicErr(it, errParseDate{it.val})
+	}
+	return t, p.typeOfPrimitive(it)
+}
+
+// Go's time.Parse() will accept numbers without a leading zero; there isn't any
+// way to require it. https://github.com/golang/go/issues/29911
+//
+// Depend on the fact that the separators (- and :) should always be at the same
+// location.
+func missingLeadingZero(d, l string) bool {
+	for i, c := range []byte(l) {
+		if c == '.' || c == 'Z' {
+			return false
+		}
+		if (c < '0' || c > '9') && d[i] != c {
+			return true
+		}
+	}
+	return false
+}
+
+func (p *parser) valueArray(it item) (any, tomlType) {
+	p.setType(p.currentKey, tomlArray, it.pos)
+
+	var (
+		// Initialize to a non-nil slice to make it consistent with how S = []
+		// decodes into a non-nil slice inside something like struct { S
+		// []string }. See #338
+		array = make([]any, 0, 2)
+	)
+	for it = p.next(); it.typ != itemArrayEnd; it = p.next() {
+		if it.typ == itemCommentStart {
+			p.expect(itemText)
+			continue
+		}
+
+		val, typ := p.value(it, true)
+		array = append(array, val)
+
+		// XXX: type isn't used here, we need it to record the accurate type
+		// information.
+		//
+		// Not entirely sure how to best store this; could use "key[0]",
+		// "key[1]" notation, or maybe store it on the Array type?
+		_ = typ
+	}
+	return array, tomlArray
+}
+
+func (p *parser) valueInlineTable(it item, parentIsArray bool) (any, tomlType) {
+	var (
+		topHash      = make(map[string]any)
+		outerContext = p.context
+		outerKey     = p.currentKey
+	)
+
+	p.context = append(p.context, p.currentKey)
+	prevContext := p.context
+	p.currentKey = ""
+
+	p.addImplicit(p.context)
+	p.addContext(p.context, parentIsArray)
+
+	/// Loop over all table key/value pairs.
+	for it := p.next(); it.typ != itemInlineTableEnd; it = p.next() {
+		if it.typ == itemCommentStart {
+			p.expect(itemText)
+			continue
+		}
+
+		/// Read all key parts.
+		k := p.nextPos()
+		var key Key
+		for ; k.typ != itemKeyEnd && k.typ != itemEOF; k = p.next() {
+			key = append(key, p.keyString(k))
+		}
+		p.assertEqual(itemKeyEnd, k.typ)
+
+		/// The current key is the last part.
+		p.currentKey = key.last()
+
+		/// All the other parts (if any) are the context; need to set each part
+		/// as implicit.
+		context := key.parent()
+		for i := range context {
+			p.addImplicitContext(append(p.context, context[i:i+1]...))
+		}
+		p.ordered = append(p.ordered, p.context.add(p.currentKey))
+
+		/// Set the value.
+		val, typ := p.value(p.next(), false)
+		p.setValue(p.currentKey, val)
+		p.setType(p.currentKey, typ, it.pos)
+
+		hash := topHash
+		for _, c := range context {
+			h, ok := hash[c]
+			if !ok {
+				h = make(map[string]any)
+				hash[c] = h
+			}
+			hash, ok = h.(map[string]any)
+			if !ok {
+				p.panicf("%q is not a table", p.context)
+			}
+		}
+		hash[p.currentKey] = val
+
+		/// Restore context.
+		p.context = prevContext
+	}
+	p.context = outerContext
+	p.currentKey = outerKey
+	return topHash, tomlHash
+}
+
+// numHasLeadingZero checks if this number has leading zeroes, allowing for '0',
+// +/- signs, and base prefixes.
+func numHasLeadingZero(s string) bool {
+	if len(s) > 1 && s[0] == '0' && !(s[1] == 'b' || s[1] == 'o' || s[1] == 'x') { // Allow 0b, 0o, 0x
+		return true
+	}
+	if len(s) > 2 && (s[0] == '-' || s[0] == '+') && s[1] == '0' {
+		return true
+	}
+	return false
+}
+
+// numUnderscoresOK checks whether each underscore in s is surrounded by
+// characters that are not underscores.
+func numUnderscoresOK(s string) bool {
+	switch s {
+	case "nan", "+nan", "-nan", "inf", "-inf", "+inf":
+		return true
+	}
+	accept := false
+	for _, r := range s {
+		if r == '_' {
+			if !accept {
+				return false
+			}
+		}
+
+		// isHex is a superset of all the permissible characters surrounding an
+		// underscore.
+		accept = isHex(r)
+	}
+	return accept
+}
+
+// numPeriodsOK checks whether every period in s is followed by a digit.
+func numPeriodsOK(s string) bool {
+	period := false
+	for _, r := range s {
+		if period && !isDigit(r) {
+			return false
+		}
+		period = r == '.'
+	}
+	return !period
+}
+
+// Set the current context of the parser, where the context is either a hash or
+// an array of hashes, depending on the value of the `array` parameter.
+//
+// Establishing the context also makes sure that the key isn't a duplicate, and
+// will create implicit hashes automatically.
+func (p *parser) addContext(key Key, array bool) {
+	/// Always start at the top level and drill down for our context.
+	hashContext := p.mapping
+	keyContext := make(Key, 0, len(key)-1)
+
+	/// We only need implicit hashes for the parents.
+	for _, k := range key.parent() {
+		_, ok := hashContext[k]
+		keyContext = append(keyContext, k)
+
+		// No key? Make an implicit hash and move on.
+		if !ok {
+			p.addImplicit(keyContext)
+			hashContext[k] = make(map[string]any)
+		}
+
+		// If the hash context is actually an array of tables, then set
+		// the hash context to the last element in that array.
+		//
+		// Otherwise, it better be a table, since this MUST be a key group (by
+		// virtue of it not being the last element in a key).
+		switch t := hashContext[k].(type) {
+		case []map[string]any:
+			hashContext = t[len(t)-1]
+		case map[string]any:
+			hashContext = t
+		default:
+			p.panicf("Key '%s' was already created as a hash.", keyContext)
+		}
+	}
+
+	p.context = keyContext
+	if array {
+		// If this is the first element for this array, then allocate a new
+		// list of tables for it.
+		k := key.last()
+		if _, ok := hashContext[k]; !ok {
+			hashContext[k] = make([]map[string]any, 0, 4)
+		}
+
+		// Add a new table. But make sure the key hasn't already been used
+		// for something else.
+		if hash, ok := hashContext[k].([]map[string]any); ok {
+			hashContext[k] = append(hash, make(map[string]any))
+		} else {
+			p.panicf("Key '%s' was already created and cannot be used as an array.", key)
+		}
+	} else {
+		p.setValue(key.last(), make(map[string]any))
+	}
+	p.context = append(p.context, key.last())
+}
+
+// setValue sets the given key to the given value in the current context.
+// It will make sure that the key hasn't already been defined, account for
+// implicit key groups.
+func (p *parser) setValue(key string, value any) {
+	var (
+		tmpHash    any
+		ok         bool
+		hash       = p.mapping
+		keyContext = make(Key, 0, len(p.context)+1)
+	)
+	for _, k := range p.context {
+		keyContext = append(keyContext, k)
+		if tmpHash, ok = hash[k]; !ok {
+			p.bug("Context for key '%s' has not been established.", keyContext)
+		}
+		switch t := tmpHash.(type) {
+		case []map[string]any:
+			// The context is a table of hashes. Pick the most recent table
+			// defined as the current hash.
+			hash = t[len(t)-1]
+		case map[string]any:
+			hash = t
+		default:
+			p.panicf("Key '%s' has already been defined.", keyContext)
+		}
+	}
+	keyContext = append(keyContext, key)
+
+	if _, ok := hash[key]; ok {
+		// Normally redefining keys isn't allowed, but the key could have been
+		// defined implicitly and it's allowed to be redefined concretely. (See
+		// the `valid/implicit-and-explicit-after.toml` in toml-test)
+		//
+		// But we have to make sure to stop marking it as an implicit. (So that
+		// another redefinition provokes an error.)
+		//
+		// Note that since it has already been defined (as a hash), we don't
+		// want to overwrite it. So our business is done.
+		if p.isArray(keyContext) {
+			if !p.isImplicit(keyContext) {
+				if _, ok := hash[key]; ok {
+					p.panicf("Key '%s' has already been defined.", keyContext)
+				}
+			}
+			p.removeImplicit(keyContext)
+			hash[key] = value
+			return
+		}
+		if p.isImplicit(keyContext) {
+			p.removeImplicit(keyContext)
+			return
+		}
+		// Otherwise, we have a concrete key trying to override a previous key,
+		// which is *always* wrong.
+		p.panicf("Key '%s' has already been defined.", keyContext)
+	}
+
+	hash[key] = value
+}
+
+// setType sets the type of a particular value at a given key. It should be
+// called immediately AFTER setValue.
+//
+// Note that if `key` is empty, then the type given will be applied to the
+// current context (which is either a table or an array of tables).
+func (p *parser) setType(key string, typ tomlType, pos Position) {
+	keyContext := make(Key, 0, len(p.context)+1)
+	keyContext = append(keyContext, p.context...)
+	if len(key) > 0 { // allow type setting for hashes
+		keyContext = append(keyContext, key)
+	}
+	// Special case to make empty keys ("" = 1) work.
+	// Without it it will set "" rather than `""`.
+	// TODO: why is this needed? And why is this only needed here?
+	if len(keyContext) == 0 {
+		keyContext = Key{""}
+	}
+	p.keyInfo[keyContext.String()] = keyInfo{tomlType: typ, pos: pos}
+}
+
+// Implicit keys need to be created when tables are implied in "a.b.c.d = 1" and
+// "[a.b.c]" (the "a", "b", and "c" hashes are never created explicitly).
+func (p *parser) addImplicit(key Key)        { p.implicits[key.String()] = struct{}{} }
+func (p *parser) removeImplicit(key Key)     { delete(p.implicits, key.String()) }
+func (p *parser) isImplicit(key Key) bool    { _, ok := p.implicits[key.String()]; return ok }
+func (p *parser) isArray(key Key) bool       { return p.keyInfo[key.String()].tomlType == tomlArray }
+func (p *parser) addImplicitContext(key Key) { p.addImplicit(key); p.addContext(key, false) }
+
+// current returns the full key name of the current context.
+func (p *parser) current() string {
+	if len(p.currentKey) == 0 {
+		return p.context.String()
+	}
+	if len(p.context) == 0 {
+		return p.currentKey
+	}
+	return fmt.Sprintf("%s.%s", p.context, p.currentKey)
+}
+
+func stripFirstNewline(s string) string {
+	if len(s) > 0 && s[0] == '\n' {
+		return s[1:]
+	}
+	if len(s) > 1 && s[0] == '\r' && s[1] == '\n' {
+		return s[2:]
+	}
+	return s
+}
+
+// stripEscapedNewlines removes whitespace after line-ending backslashes in
+// multiline strings.
+//
+// A line-ending backslash is an unescaped \ followed only by whitespace until
+// the next newline. After a line-ending backslash, all whitespace is removed
+// until the next non-whitespace character.
+func (p *parser) stripEscapedNewlines(s string) string {
+	var (
+		b strings.Builder
+		i int
+	)
+	b.Grow(len(s))
+	for {
+		ix := strings.Index(s[i:], `\`)
+		if ix < 0 {
+			b.WriteString(s)
+			return b.String()
+		}
+		i += ix
+
+		if len(s) > i+1 && s[i+1] == '\\' {
+			// Escaped backslash.
+			i += 2
+			continue
+		}
+		// Scan until the next non-whitespace.
+		j := i + 1
+	whitespaceLoop:
+		for ; j < len(s); j++ {
+			switch s[j] {
+			case ' ', '\t', '\r', '\n':
+			default:
+				break whitespaceLoop
+			}
+		}
+		if j == i+1 {
+			// Not a whitespace escape.
+			i++
+			continue
+		}
+		if !strings.Contains(s[i:j], "\n") {
+			// This is not a line-ending backslash. (It's a bad escape sequence,
+			// but we can let replaceEscapes catch it.)
+			i++
+			continue
+		}
+		b.WriteString(s[:i])
+		s = s[j:]
+		i = 0
+	}
+}
+
+func (p *parser) replaceEscapes(it item, str string) string {
+	var (
+		b    strings.Builder
+		skip = 0
+	)
+	b.Grow(len(str))
+	for i, c := range str {
+		if skip > 0 {
+			skip--
+			continue
+		}
+		if c != '\\' {
+			b.WriteRune(c)
+			continue
+		}
+
+		if i >= len(str) {
+			p.bug("Escape sequence at end of string.")
+			return ""
+		}
+		switch str[i+1] {
+		default:
+			p.bug("Expected valid escape code after \\, but got %q.", str[i+1])
+		case ' ', '\t':
+			p.panicItemf(it, "invalid escape: '\\%c'", str[i+1])
+		case 'b':
+			b.WriteByte(0x08)
+			skip = 1
+		case 't':
+			b.WriteByte(0x09)
+			skip = 1
+		case 'n':
+			b.WriteByte(0x0a)
+			skip = 1
+		case 'f':
+			b.WriteByte(0x0c)
+			skip = 1
+		case 'r':
+			b.WriteByte(0x0d)
+			skip = 1
+		case 'e':
+			b.WriteByte(0x1b)
+			skip = 1
+		case '"':
+			b.WriteByte(0x22)
+			skip = 1
+		case '\\':
+			b.WriteByte(0x5c)
+			skip = 1
+		// The lexer guarantees the correct number of characters are present;
+		// don't need to check here.
+		case 'x':
+			escaped := p.asciiEscapeToUnicode(it, str[i+2:i+4])
+			b.WriteRune(escaped)
+			skip = 3
+		case 'u':
+			escaped := p.asciiEscapeToUnicode(it, str[i+2:i+6])
+			b.WriteRune(escaped)
+			skip = 5
+		case 'U':
+			escaped := p.asciiEscapeToUnicode(it, str[i+2:i+10])
+			b.WriteRune(escaped)
+			skip = 9
+		}
+	}
+	return b.String()
+}
+
+func (p *parser) asciiEscapeToUnicode(it item, s string) rune {
+	hex, err := strconv.ParseUint(strings.ToLower(s), 16, 32)
+	if err != nil {
+		p.bug("Could not parse '%s' as a hexadecimal number, but the lexer claims it's OK: %s", s, err)
+	}
+	if !utf8.ValidRune(rune(hex)) {
+		p.panicItemf(it, "Escaped character '\\u%s' is not valid UTF-8.", s)
+	}
+	return rune(hex)
+}
@@ -0,0 +1,238 @@
+package toml
+
+// Struct field handling is adapted from code in encoding/json:
+//
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the Go distribution.
+
+import (
+	"reflect"
+	"sort"
+	"sync"
+)
+
+// A field represents a single field found in a struct.
+type field struct {
+	name  string       // the name of the field (`toml` tag included)
+	tag   bool         // whether field has a `toml` tag
+	index []int        // represents the depth of an anonymous field
+	typ   reflect.Type // the type of the field
+}
+
+// byName sorts field by name, breaking ties with depth,
+// then breaking ties with "name came from toml tag", then
+// breaking ties with index sequence.
+type byName []field
+
+func (x byName) Len() int      { return len(x) }
+func (x byName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+func (x byName) Less(i, j int) bool {
+	if x[i].name != x[j].name {
+		return x[i].name < x[j].name
+	}
+	if len(x[i].index) != len(x[j].index) {
+		return len(x[i].index) < len(x[j].index)
+	}
+	if x[i].tag != x[j].tag {
+		return x[i].tag
+	}
+	return byIndex(x).Less(i, j)
+}
+
+// byIndex sorts field by index sequence.
+type byIndex []field
+
+func (x byIndex) Len() int      { return len(x) }
+func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+func (x byIndex) Less(i, j int) bool {
+	for k, xik := range x[i].index {
+		if k >= len(x[j].index) {
+			return false
+		}
+		if xik != x[j].index[k] {
+			return xik < x[j].index[k]
+		}
+	}
+	return len(x[i].index) < len(x[j].index)
+}
+
+// typeFields returns a list of fields that TOML should recognize for the given
+// type. The algorithm is breadth-first search over the set of structs to
+// include - the top struct and then any reachable anonymous structs.
+func typeFields(t reflect.Type) []field {
+	// Anonymous fields to explore at the current level and the next.
+	current := []field{}
+	next := []field{{typ: t}}
+
+	// Count of queued names for current level and the next.
+	var count map[reflect.Type]int
+	var nextCount map[reflect.Type]int
+
+	// Types already visited at an earlier level.
+	visited := map[reflect.Type]bool{}
+
+	// Fields found.
+	var fields []field
+
+	for len(next) > 0 {
+		current, next = next, current[:0]
+		count, nextCount = nextCount, map[reflect.Type]int{}
+
+		for _, f := range current {
+			if visited[f.typ] {
+				continue
+			}
+			visited[f.typ] = true
+
+			// Scan f.typ for fields to include.
+			for i := 0; i < f.typ.NumField(); i++ {
+				sf := f.typ.Field(i)
+				if sf.PkgPath != "" && !sf.Anonymous { // unexported
+					continue
+				}
+				opts := getOptions(sf.Tag)
+				if opts.skip {
+					continue
+				}
+				index := make([]int, len(f.index)+1)
+				copy(index, f.index)
+				index[len(f.index)] = i
+
+				ft := sf.Type
+				if ft.Name() == "" && ft.Kind() == reflect.Ptr {
+					// Follow pointer.
+					ft = ft.Elem()
+				}
+
+				// Record found field and index sequence.
+				if opts.name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
+					tagged := opts.name != ""
+					name := opts.name
+					if name == "" {
+						name = sf.Name
+					}
+					fields = append(fields, field{name, tagged, index, ft})
+					if count[f.typ] > 1 {
+						// If there were multiple instances, add a second,
+						// so that the annihilation code will see a duplicate.
+						// It only cares about the distinction between 1 or 2,
+						// so don't bother generating any more copies.
+						fields = append(fields, fields[len(fields)-1])
+					}
+					continue
+				}
+
+				// Record new anonymous struct to explore in next round.
+				nextCount[ft]++
+				if nextCount[ft] == 1 {
+					f := field{name: ft.Name(), index: index, typ: ft}
+					next = append(next, f)
+				}
+			}
+		}
+	}
+
+	sort.Sort(byName(fields))
+
+	// Delete all fields that are hidden by the Go rules for embedded fields,
+	// except that fields with TOML tags are promoted.
+
+	// The fields are sorted in primary order of name, secondary order
+	// of field index length. Loop over names; for each name, delete
+	// hidden fields by choosing the one dominant field that survives.
+	out := fields[:0]
+	for advance, i := 0, 0; i < len(fields); i += advance {
+		// One iteration per name.
+		// Find the sequence of fields with the name of this first field.
+		fi := fields[i]
+		name := fi.name
+		for advance = 1; i+advance < len(fields); advance++ {
+			fj := fields[i+advance]
+			if fj.name != name {
+				break
+			}
+		}
+		if advance == 1 { // Only one field with this name
+			out = append(out, fi)
+			continue
+		}
+		dominant, ok := dominantField(fields[i : i+advance])
+		if ok {
+			out = append(out, dominant)
+		}
+	}
+
+	fields = out
+	sort.Sort(byIndex(fields))
+
+	return fields
+}
+
+// dominantField looks through the fields, all of which are known to
+// have the same name, to find the single field that dominates the
+// others using Go's embedding rules, modified by the presence of
+// TOML tags. If there are multiple top-level fields, the boolean
+// will be false: This condition is an error in Go and we skip all
+// the fields.
+func dominantField(fields []field) (field, bool) {
+	// The fields are sorted in increasing index-length order. The winner
+	// must therefore be one with the shortest index length. Drop all
+	// longer entries, which is easy: just truncate the slice.
+	length := len(fields[0].index)
+	tagged := -1 // Index of first tagged field.
+	for i, f := range fields {
+		if len(f.index) > length {
+			fields = fields[:i]
+			break
+		}
+		if f.tag {
+			if tagged >= 0 {
+				// Multiple tagged fields at the same level: conflict.
+				// Return no field.
+				return field{}, false
+			}
+			tagged = i
+		}
+	}
+	if tagged >= 0 {
+		return fields[tagged], true
+	}
+	// All remaining fields have the same length. If there's more than one,
+	// we have a conflict (two fields named "X" at the same level) and we
+	// return no field.
+	if len(fields) > 1 {
+		return field{}, false
+	}
+	return fields[0], true
+}
+
+var fieldCache struct {
+	sync.RWMutex
+	m map[reflect.Type][]field
+}
+
+// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
+func cachedTypeFields(t reflect.Type) []field {
+	fieldCache.RLock()
+	f := fieldCache.m[t]
+	fieldCache.RUnlock()
+	if f != nil {
+		return f
+	}
+
+	// Compute fields without lock.
+	// Might duplicate effort but won't hold other computations back.
+	f = typeFields(t)
+	if f == nil {
+		f = []field{}
+	}
+
+	fieldCache.Lock()
+	if fieldCache.m == nil {
+		fieldCache.m = map[reflect.Type][]field{}
+	}
+	fieldCache.m[t] = f
+	fieldCache.Unlock()
+	return f
+}
@@ -0,0 +1,65 @@
+package toml
+
+// tomlType represents any Go type that corresponds to a TOML type.
+// While the first draft of the TOML spec has a simplistic type system that
+// probably doesn't need this level of sophistication, we seem to be militating
+// toward adding real composite types.
+type tomlType interface {
+	typeString() string
+}
+
+// typeEqual accepts any two types and returns true if they are equal.
+func typeEqual(t1, t2 tomlType) bool {
+	if t1 == nil || t2 == nil {
+		return false
+	}
+	return t1.typeString() == t2.typeString()
+}
+
+func typeIsTable(t tomlType) bool {
+	return typeEqual(t, tomlHash) || typeEqual(t, tomlArrayHash)
+}
+
+type tomlBaseType string
+
+func (btype tomlBaseType) typeString() string { return string(btype) }
+func (btype tomlBaseType) String() string     { return btype.typeString() }
+
+var (
+	tomlInteger   tomlBaseType = "Integer"
+	tomlFloat     tomlBaseType = "Float"
+	tomlDatetime  tomlBaseType = "Datetime"
+	tomlString    tomlBaseType = "String"
+	tomlBool      tomlBaseType = "Bool"
+	tomlArray     tomlBaseType = "Array"
+	tomlHash      tomlBaseType = "Hash"
+	tomlArrayHash tomlBaseType = "ArrayHash"
+)
+
+// typeOfPrimitive returns a tomlType of any primitive value in TOML.
+// Primitive values are: Integer, Float, Datetime, String and Bool.
+//
+// Passing a lexer item other than the following will cause a BUG message
+// to occur: itemString, itemBool, itemInteger, itemFloat, itemDatetime.
+func (p *parser) typeOfPrimitive(lexItem item) tomlType {
+	switch lexItem.typ {
+	case itemInteger:
+		return tomlInteger
+	case itemFloat:
+		return tomlFloat
+	case itemDatetime:
+		return tomlDatetime
+	case itemString, itemStringEsc:
+		return tomlString
+	case itemMultilineString:
+		return tomlString
+	case itemRawString:
+		return tomlString
+	case itemRawMultilineString:
+		return tomlString
+	case itemBool:
+		return tomlBool
+	}
+	p.bug("Cannot infer primitive type of lex item '%s'.", lexItem)
+	panic("unreachable")
+}
@@ -0,0 +1,9 @@
+The MIT License
+
+Copyright (c) 2016 Creston Bunch
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
@@ -0,0 +1,58 @@
+[![Go](https://github.com/CiscoM31/godata/actions/workflows/go.yml/badge.svg)](https://github.com/CiscoM31/godata/actions/workflows/go.yml)
+[![golangci-lint](https://github.com/CiscoM31/godata/actions/workflows/golangci-lint.yml/badge.svg)](https://github.com/CiscoM31/godata/actions/workflows/golangci-lint.yml)
+
+GoData
+======
+
+This is an implementation of OData in Go. It is capable of parsing an OData
+request, and exposing it in a standard way so that any provider can consume
+OData requests and produce a response. Providers can be written for general
+usage like producing SQL statements for a databases, or very specific uses like
+connecting to another API.
+
+Most OData server frameworks are C#/.NET or Java. These require using the CLR or
+JVM, and are overkill for a lot of use cases. By using Go we aim to provide a
+lightweight, fast, and concurrent OData service. By exposing a generic interface
+to an OData request, we hope to enable any backend to expose itself with
+an OData API with as little effort as possible.
+
+Status
+======
+
+This project is not finished yet, and cannot be used in its current state.
+Progress is underway to make it usable, and eventually fully compatible with the
+OData V4 specification.
+
+Work in Progress
+================
+
+* ~~Parse OData URLs~~
+* Create provider interface for GET requests
+* Parse OData POST and PATCH requests
+* Create provider interface for POST and PATCH requests
+* Parse OData DELETE requests
+* Create provider interface for PATCH requests
+* Allow injecting middleware into the request pipeline to enable such features
+  as caching, authentication, telemetry, etc.
+* Work on fully supporting the OData specification with unit tests
+
+Feel free to contribute with any of these tasks.
+
+High Level Architecture
+=======================
+
+If you're interesting in helping out, here is a quick introduction to the
+code to help you understand the process. The code works something like this:
+
+1. A provider is initialized that defines the object model (i.e., metadata), of
+   the OData service. (See the example directory.)
+2. An HTTP request is received by the request handler in service.go
+3. The URL is parsed into a data structure defined in request_model.go
+4. The request model is semanticized, so each piece of the request is associated
+   with an entity/type/collection/etc. in the provider object model.
+5. The correct method and type of request (entity, collection, $metadata, $ref, 
+   property, etc.) is determined from the semantic information.
+6. The request is then delegated to the appropriate method of a GoDataProvider,
+   which will produce a response based on the semantic information, and
+   package it into a response defined in response_model.go.
+7. The response is converted to JSON and sent back to the client.
@@ -0,0 +1,8 @@
+package godata
+
+import "context"
+
+func ParseApplyString(ctx context.Context, apply string) (*GoDataApplyQuery, error) {
+	result := GoDataApplyQuery(apply)
+	return &result, nil
+}
@@ -0,0 +1,149 @@
+package godata
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// The $compute query option must have a value which is a comma separated list of <expression> as <dynamic property name>
+// See https://docs.oasis-open.org/odata/odata/v4.01/os/part2-url-conventions/odata-v4.01-os-part2-url-conventions.html#sec_SystemQueryOptioncompute
+const computeAsSeparator = " as "
+
+// Dynamic property names are restricted to case-insensitive a-z and the path separator /.
+var computeFieldRegex = regexp.MustCompile("^[a-zA-Z/]+$")
+
+type ComputeItem struct {
+	Tree  *ParseNode // The compute expression parsed as a tree.
+	Field string     // The name of the computed dynamic property.
+}
+
+// GlobalAllTokenParser is a Tokenizer which matches all tokens and ignores none. It differs from the
+// GlobalExpressionTokenizer which ignores whitespace tokens.
+var GlobalAllTokenParser *Tokenizer
+
+func init() {
+	t := NewExpressionParser().tokenizer
+	t.TokenMatchers = append(t.IgnoreMatchers, t.TokenMatchers...)
+	t.IgnoreMatchers = nil
+	GlobalAllTokenParser = t
+}
+
+func ParseComputeString(ctx context.Context, compute string) (*GoDataComputeQuery, error) {
+	items, err := SplitComputeItems(compute)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]*ComputeItem, 0)
+	fields := map[string]struct{}{}
+
+	for _, v := range items {
+		v = strings.TrimSpace(v)
+		parts := strings.Split(v, computeAsSeparator)
+		if len(parts) != 2 {
+			return nil, &GoDataError{
+				ResponseCode: 400,
+				Message:      "Invalid $compute query option",
+			}
+		}
+		field := strings.TrimSpace(parts[1])
+		if !computeFieldRegex.MatchString(field) {
+			return nil, &GoDataError{
+				ResponseCode: 400,
+				Message:      "Invalid $compute query option",
+			}
+		}
+
+		if tree, err := GlobalExpressionParser.ParseExpressionString(ctx, parts[0]); err != nil {
+			switch e := err.(type) {
+			case *GoDataError:
+				return nil, &GoDataError{
+					ResponseCode: e.ResponseCode,
+					Message:      fmt.Sprintf("Invalid $compute query option, %s", e.Message),
+					Cause:        e,
+				}
+			default:
+				return nil, &GoDataError{
+					ResponseCode: 500,
+					Message:      "Invalid $compute query option",
+					Cause:        e,
+				}
+			}
+		} else {
+			if tree == nil {
+				return nil, &GoDataError{
+					ResponseCode: 500,
+					Message:      "Invalid $compute query option",
+				}
+			}
+
+			if _, ok := fields[field]; ok {
+				return nil, &GoDataError{
+					ResponseCode: 400,
+					Message:      "Invalid $compute query option",
+				}
+			}
+
+			fields[field] = struct{}{}
+
+			result = append(result, &ComputeItem{
+				Tree:  tree.Tree,
+				Field: field,
+			})
+		}
+	}
+
+	return &GoDataComputeQuery{result, compute}, nil
+}
+
+// SplitComputeItems splits the input string based on the comma delimiter. It does so with awareness as to
+// which commas delimit $compute items and which ones are an inline part of the item, such as a separator
+// for function arguments.
+//
+// For example the input "someFunc(one,two) as three, 1 add 2 as four" results in the
+// output ["someFunc(one,two) as three", "1 add 2 as four"]
+func SplitComputeItems(in string) ([]string, error) {
+
+	var ret []string
+
+	tokens, err := GlobalAllTokenParser.Tokenize(context.Background(), in)
+	if err != nil {
+		return nil, err
+	}
+
+	item := strings.Builder{}
+	parenGauge := 0
+
+	for _, v := range tokens {
+		switch v.Type {
+		case ExpressionTokenOpenParen:
+			parenGauge++
+		case ExpressionTokenCloseParen:
+			if parenGauge == 0 {
+				return nil, errors.New("unmatched parentheses")
+			}
+			parenGauge--
+		case ExpressionTokenComma:
+			if parenGauge == 0 {
+				ret = append(ret, item.String())
+				item.Reset()
+				continue
+			}
+		}
+
+		item.WriteString(v.Value)
+	}
+
+	if parenGauge != 0 {
+		return nil, errors.New("unmatched parentheses")
+	}
+
+	if item.Len() > 0 {
+		ret = append(ret, item.String())
+	}
+
+	return ret, nil
+}
@@ -0,0 +1,17 @@
+package godata
+
+import (
+	"context"
+	"strconv"
+)
+
+func ParseCountString(ctx context.Context, count string) (*GoDataCountQuery, error) {
+	i, err := strconv.ParseBool(count)
+	if err != nil {
+		return nil, err
+	}
+
+	result := GoDataCountQuery(i)
+
+	return &result, nil
+}
@@ -0,0 +1,69 @@
+package godata
+
+import "fmt"
+
+type GoDataError struct {
+	ResponseCode int
+	Message      string
+	Cause        error
+}
+
+func (err *GoDataError) Error() string {
+	if err.Cause != nil {
+		return fmt.Sprintf("%s. Cause: %s", err.Message, err.Cause.Error())
+	}
+	return err.Message
+}
+
+func (err *GoDataError) Unwrap() error {
+	return err.Cause
+}
+
+func (err *GoDataError) SetCause(e error) *GoDataError {
+	err.Cause = e
+	return err
+}
+
+func BadRequestError(message string) *GoDataError {
+	return &GoDataError{400, message, nil}
+}
+
+func NotFoundError(message string) *GoDataError {
+	return &GoDataError{404, message, nil}
+}
+
+func MethodNotAllowedError(message string) *GoDataError {
+	return &GoDataError{405, message, nil}
+}
+
+func GoneError(message string) *GoDataError {
+	return &GoDataError{410, message, nil}
+}
+
+func PreconditionFailedError(message string) *GoDataError {
+	return &GoDataError{412, message, nil}
+}
+
+func InternalServerError(message string) *GoDataError {
+	return &GoDataError{500, message, nil}
+}
+
+func NotImplementedError(message string) *GoDataError {
+	return &GoDataError{501, message, nil}
+}
+
+type UnsupportedQueryParameterError struct {
+	Parameter string
+}
+
+func (err *UnsupportedQueryParameterError) Error() string {
+	return fmt.Sprintf("Query parameter '%s' is not supported", err.Parameter)
+}
+
+type DuplicateQueryParameterError struct {
+	Parameter string
+}
+
+func (err *DuplicateQueryParameterError) Error() string {
+	return fmt.Sprintf("Query parameter '%s' cannot be specified more than once", err.Parameter)
+}
@@ -0,0 +1,409 @@
+package godata
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+)
+
+type ExpandTokenType int
+
+func (e ExpandTokenType) Value() int {
+	return (int)(e)
+}
+
+const (
+	ExpandTokenOpenParen ExpandTokenType = iota
+	ExpandTokenCloseParen
+	ExpandTokenNav
+	ExpandTokenComma
+	ExpandTokenSemicolon
+	ExpandTokenEquals
+	ExpandTokenLiteral
+)
+
+var GlobalExpandTokenizer = ExpandTokenizer()
+
+// Represents an item to expand in an OData query. Tracks the path of the entity
+// to expand and also the filter, levels, and reference options, etc.
+type ExpandItem struct {
+	Path    []*Token
+	Filter  *GoDataFilterQuery
+	At      *GoDataFilterQuery
+	Search  *GoDataSearchQuery
+	OrderBy *GoDataOrderByQuery
+	Skip    *GoDataSkipQuery
+	Top     *GoDataTopQuery
+	Select  *GoDataSelectQuery
+	Compute *GoDataComputeQuery
+	Expand  *GoDataExpandQuery
+	Levels  int
+}
+
+func ExpandTokenizer() *Tokenizer {
+	t := Tokenizer{}
+	t.Add("^\\(", ExpandTokenOpenParen)
+	t.Add("^\\)", ExpandTokenCloseParen)
+	t.Add("^/", ExpandTokenNav)
+	t.Add("^,", ExpandTokenComma)
+	t.Add("^;", ExpandTokenSemicolon)
+	t.Add("^=", ExpandTokenEquals)
+	t.Add("^[a-zA-Z0-9_\\'\\.:\\$ \\*]+", ExpandTokenLiteral)
+
+	return &t
+}
+
+func ParseExpandString(ctx context.Context, expand string) (*GoDataExpandQuery, error) {
+	tokens, err := GlobalExpandTokenizer.Tokenize(ctx, expand)
+
+	if err != nil {
+		return nil, err
+	}
+
+	stack := tokenStack{}
+	queue := tokenQueue{}
+	items := make([]*ExpandItem, 0)
+
+	for len(tokens) > 0 {
+		token := tokens[0]
+		tokens = tokens[1:]
+
+		if token.Value == "(" {
+			queue.Enqueue(token)
+			stack.Push(token)
+		} else if token.Value == ")" {
+			queue.Enqueue(token)
+			stack.Pop()
+		} else if token.Value == "," {
+			if stack.Empty() {
+				// no paren on the stack, parse this item and start a new queue
+				item, err := ParseExpandItem(ctx, queue)
+				if err != nil {
+					return nil, err
+				}
+				items = append(items, item)
+				queue = tokenQueue{}
+			} else {
+				// this comma is inside a nested expression, keep it in the queue
+				queue.Enqueue(token)
+			}
+		} else {
+			queue.Enqueue(token)
+		}
+	}
+
+	if !stack.Empty() {
+		return nil, BadRequestError("Mismatched parentheses in expand clause.")
+	}
+
+	item, err := ParseExpandItem(ctx, queue)
+	if err != nil {
+		return nil, err
+	}
+	items = append(items, item)
+
+	return &GoDataExpandQuery{ExpandItems: items}, nil
+}
+
+func ParseExpandItem(ctx context.Context, input tokenQueue) (*ExpandItem, error) {
+
+	item := &ExpandItem{}
+	item.Path = []*Token{}
+
+	stack := &tokenStack{}
+	queue := &tokenQueue{}
+
+	for !input.Empty() {
+		token := input.Dequeue()
+		if token.Value == "(" {
+			if !stack.Empty() {
+				// this is a nested slash, it belongs on the queue
+				queue.Enqueue(token)
+			} else {
+				// top level slash means we're done parsing the path
+				item.Path = append(item.Path, queue.Dequeue())
+			}
+			stack.Push(token)
+		} else if token.Value == ")" {
+			stack.Pop()
+			if !stack.Empty() {
+				// this is a nested slash, it belongs on the queue
+				queue.Enqueue(token)
+			} else {
+				// top level slash means we're done parsing the options
+				err := ParseExpandOption(ctx, queue, item)
+				if err != nil {
+					return nil, err
+				}
+				// reset the queue
+				queue = &tokenQueue{}
+			}
+		} else if token.Value == "/" && stack.Empty() {
+			if queue.Empty() {
+				// Disallow extra leading and intermediate slash, like /Product and Product//Info
+				return nil, BadRequestError("Empty path segment in expand clause.")
+			}
+			if input.Empty() {
+				// Disallow extra trailing slash, like Product/
+				return nil, BadRequestError("Empty path segment in expand clause.")
+			}
+			// at root level, slashes separate path segments
+			item.Path = append(item.Path, queue.Dequeue())
+		} else if token.Value == ";" && stack.Size == 1 {
+			// semicolons only split expand options at the first level
+			err := ParseExpandOption(ctx, queue, item)
+			if err != nil {
+				return nil, err
+			}
+			// reset the queue
+			queue = &tokenQueue{}
+		} else {
+			queue.Enqueue(token)
+		}
+	}
+
+	if !stack.Empty() {
+		return nil, BadRequestError("Mismatched parentheses in expand clause.")
+	}
+
+	if !queue.Empty() {
+		item.Path = append(item.Path, queue.Dequeue())
+	}
+
+	cfg, hasComplianceConfig := ctx.Value(odataCompliance).(OdataComplianceConfig)
+	if !hasComplianceConfig {
+		// Strict ODATA compliance by default.
+		cfg = ComplianceStrict
+	}
+
+	if len(item.Path) == 0 && cfg&ComplianceIgnoreInvalidComma == 0 {
+		return nil, BadRequestError("Extra comma in $expand.")
+	}
+
+	return item, nil
+}
+
+func ParseExpandOption(ctx context.Context, queue *tokenQueue, item *ExpandItem) error {
+	head := queue.Dequeue().Value
+	if queue.Head == nil {
+		return BadRequestError("Invalid expand clause.")
+	}
+	queue.Dequeue() // drop the '=' from the front of the queue
+	body := queue.GetValue()
+
+	cfg, hasComplianceConfig := ctx.Value(odataCompliance).(OdataComplianceConfig)
+	if !hasComplianceConfig {
+		// Strict ODATA compliance by default.
+		cfg = ComplianceStrict
+	}
+
+	if cfg == ComplianceStrict {
+		// Enforce that only supported keywords are specified in expand.
+		// The $levels keyword supported within expand is checked explicitly in addition to
+		// keywords listed in supportedOdataKeywords[] which are permitted within expand and
+		// at the top level of the odata query.
+		if _, ok := supportedOdataKeywords[head]; !ok && head != "$levels" {
+			return BadRequestError(fmt.Sprintf("Unsupported item '%s' in expand clause.", head))
+		}
+	}
+
+	if head == "$filter" {
+		filter, err := ParseFilterString(ctx, body)
+		if err == nil {
+			item.Filter = filter
+		} else {
+			return err
+		}
+	}
+
+	if head == "at" {
+		at, err := ParseFilterString(ctx, body)
+		if err == nil {
+			item.At = at
+		} else {
+			return err
+		}
+	}
+
+	if head == "$search" {
+		search, err := ParseSearchString(ctx, body)
+		if err == nil {
+			item.Search = search
+		} else {
+			return err
+		}
+	}
+
+	if head == "$orderby" {
+		orderby, err := ParseOrderByString(ctx, body)
+		if err == nil {
+			item.OrderBy = orderby
+		} else {
+			return err
+		}
+	}
+
+	if head == "$skip" {
+		skip, err := ParseSkipString(ctx, body)
+		if err == nil {
+			item.Skip = skip
+		} else {
+			return err
+		}
+	}
+
+	if head == "$top" {
+		top, err := ParseTopString(ctx, body)
+		if err == nil {
+			item.Top = top
+		} else {
+			return err
+		}
+	}
+
+	if head == "$select" {
+		sel, err := ParseSelectString(ctx, body)
+		if err == nil {
+			item.Select = sel
+		} else {
+			return err
+		}
+	}
+
+	if head == "$compute" {
+		comp, err := ParseComputeString(ctx, body)
+		if err == nil {
+			item.Compute = comp
+		} else {
+			return err
+		}
+	}
+
+	if head == "$expand" {
+		expand, err := ParseExpandString(ctx, body)
+		if err == nil {
+			item.Expand = expand
+		} else {
+			return err
+		}
+	}
+
+	if head == "$levels" {
+		i, err := strconv.Atoi(body)
+		if err != nil {
+			return err
+		}
+		item.Levels = i
+	}
+
+	return nil
+}
+
+func SemanticizeExpandQuery(
+	expand *GoDataExpandQuery,
+	service *GoDataService,
+	entity *GoDataEntityType,
+) error {
+
+	if expand == nil {
+		return nil
+	}
+
+	// Replace $levels with a nested expand clause
+	for _, item := range expand.ExpandItems {
+		if item.Levels > 0 {
+			if item.Expand == nil {
+				item.Expand = &GoDataExpandQuery{[]*ExpandItem{}}
+			}
+			// Future recursive calls to SemanticizeExpandQuery() will build out
+			// this expand tree completely
+			item.Expand.ExpandItems = append(
+				item.Expand.ExpandItems,
+				&ExpandItem{
+					Path:   item.Path,
+					Levels: item.Levels - 1,
+				},
+			)
+			item.Levels = 0
+		}
+	}
+
+	// we're gonna rebuild the items list, replacing wildcards where possible
+	// TODO: can we save the garbage collector some heartache?
+	newItems := []*ExpandItem{}
+
+	for _, item := range expand.ExpandItems {
+		if item.Path[0].Value == "*" {
+			// replace wildcard with a copy of every navigation property
+			for _, navProp := range service.NavigationPropertyLookup[entity] {
+				path := []*Token{{Value: navProp.Name, Type: ExpandTokenLiteral}}
+				newItem := &ExpandItem{
+					Path:   append(path, item.Path[1:]...),
+					Levels: item.Levels,
+					Expand: item.Expand,
+				}
+				newItems = append(newItems, newItem)
+			}
+			// TODO: check for duplicates?
+		} else {
+			newItems = append(newItems, item)
+		}
+	}
+
+	expand.ExpandItems = newItems
+
+	for _, item := range expand.ExpandItems {
+		err := semanticizeExpandItem(item, service, entity)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func semanticizeExpandItem(
+	item *ExpandItem,
+	service *GoDataService,
+	entity *GoDataEntityType,
+) error {
+
+	// TODO: allow multiple path segments in expand clause
+	// TODO: handle $ref
+	if len(item.Path) > 1 {
+		return NotImplementedError("Multiple path segments not currently supported in expand clauses.")
+	}
+
+	navProps := service.NavigationPropertyLookup[entity]
+	target := item.Path[len(item.Path)-1]
+	if prop, ok := navProps[target.Value]; ok {
+		target.SemanticType = SemanticTypeEntity
+		entityType, err := service.LookupEntityType(prop.Type)
+		if err != nil {
+			return err
+		}
+		target.SemanticReference = entityType
+
+		err = SemanticizeFilterQuery(item.Filter, service, entityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeExpandQuery(item.Expand, service, entityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeSelectQuery(item.Select, service, entityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeOrderByQuery(item.OrderBy, service, entityType)
+		if err != nil {
+			return err
+		}
+
+	} else {
+		return BadRequestError("Entity type " + entity.Name + " has no navigational property " + target.Value)
+	}
+
+	return nil
+}
@@ -0,0 +1,371 @@
+package godata
+
+import (
+	"context"
+	"strings"
+)
+
+// tokenDurationRe is a regex for a token of type duration.
+// The token value is set to the ISO 8601 string inside the single quotes
+// For example, if the input data is duration'PT2H', then the token value is set to PT2H without quotes.
+const tokenDurationRe = `^(duration)?'(?P<subtoken>-?P((([0-9]+Y([0-9]+M)?([0-9]+D)?|([0-9]+M)([0-9]+D)?|([0-9]+D))(T(([0-9]+H)([0-9]+M)?([0-9]+(\.[0-9]+)?S)?|([0-9]+M)([0-9]+(\.[0-9]+)?S)?|([0-9]+(\.[0-9]+)?S)))?)|(T(([0-9]+H)([0-9]+M)?([0-9]+(\.[0-9]+)?S)?|([0-9]+M)([0-9]+(\.[0-9]+)?S)?|([0-9]+(\.[0-9]+)?S)))))'`
+
+// Addressing properties.
+// Addressing items within a collection:
+//   ABNF: entityColNavigationProperty [ collectionNavigation ]
+//         collectionNavigation = [ "/" qualifiedEntityTypeName ] [ collectionNavPath ]
+//   Description: OData identifier, optionally followed by collection navigation.
+//
+// propertyPath = entityColNavigationProperty [ collectionNavigation ]
+//             / entityNavigationProperty    [ singleNavigation ]
+//             / complexColProperty          [ collectionPath ]
+//             / complexProperty             [ complexPath ]
+//             / primitiveColProperty        [ collectionPath ]
+//             / primitiveProperty           [ singlePath ]
+//             / streamProperty              [ boundOperation ]
+
+type ExpressionTokenType int
+
+func (e ExpressionTokenType) Value() int {
+	return (int)(e)
+}
+
+const (
+	ExpressionTokenOpenParen        ExpressionTokenType = iota // Open parenthesis - parenthesis expression, list expression, or path segment selector.
+	ExpressionTokenCloseParen                                  // Close parenthesis
+	ExpressionTokenWhitespace                                  // white space token
+	ExpressionTokenNav                                         // Property navigation
+	ExpressionTokenColon                                       // Function arg separator for 'any(v:boolExpr)' and 'all(v:boolExpr)' lambda operators
+	ExpressionTokenComma                                       // [5] List delimiter and function argument delimiter.
+	ExpressionTokenLogical                                     // eq|ne|gt|ge|lt|le|and|or|not|has|in
+	ExpressionTokenOp                                          // add|sub|mul|divby|div|mod
+	ExpressionTokenFunc                                        // Function, e.g. contains, substring...
+	ExpressionTokenLambdaNav                                   // "/" token when used in lambda expression, e.g. tags/any()
+	ExpressionTokenLambda                                      // [10] any(), all() lambda functions
+	ExpressionTokenCase                                        // A case() statement. See https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_case
+	ExpressionTokenCasePair                                    // A case statement expression pair [ <boolean expression> : <value expression> ]
+	ExpressionTokenNull                                        //
+	ExpressionTokenIt                                          // The '$it' token
+	ExpressionTokenRoot                                        // [15] The '$root' token
+	ExpressionTokenFloat                                       // A floating point value.
+	ExpressionTokenInteger                                     // An integer value
+	ExpressionTokenString                                      // SQUOTE *( SQUOTE-in-string / pchar-no-SQUOTE ) SQUOTE
+	ExpressionTokenDate                                        // A date value
+	ExpressionTokenTime                                        // [20] A time value
+	ExpressionTokenDateTime                                    // A date-time value
+	ExpressionTokenBoolean                                     // A literal boolean value
+	ExpressionTokenLiteral                                     // A literal non-boolean value
+	ExpressionTokenDuration                                    // duration      = [ "duration" ] SQUOTE durationValue SQUOTE
+	ExpressionTokenGuid                                        // [25] A 128-bit GUID
+	ExpressionTokenAssignement                                 // The '=' assignement for function arguments.
+	ExpressionTokenGeographyPolygon                            // A polygon with geodetic (ie spherical) coordinates. Parsed Token.Value is '<long> <lat>,<long> <lat>...'
+	ExpressionTokenGeometryPolygon                             // A polygon with planar (ie cartesian) coordinates. Parsed Token.Value is '<long> <lat>,<long> <lat>...'
+	ExpressionTokenGeographyPoint                              // A geodetic coordinate point. Parsed Token.Value is '<long> <lat>'
+	expressionTokenLast
+)
+
+func (e ExpressionTokenType) String() string {
+	return [...]string{
+		"ExpressionTokenOpenParen",
+		"ExpressionTokenCloseParen",
+		"ExpressionTokenWhitespace",
+		"ExpressionTokenNav",
+		"ExpressionTokenColon",
+		"ExpressionTokenComma",
+		"ExpressionTokenLogical",
+		"ExpressionTokenOp",
+		"ExpressionTokenFunc",
+		"ExpressionTokenLambdaNav",
+		"ExpressionTokenLambda",
+		"ExpressionTokenCase",
+		"ExpressionTokenCasePair",
+		"ExpressionTokenNull",
+		"ExpressionTokenIt",
+		"ExpressionTokenRoot",
+		"ExpressionTokenFloat",
+		"ExpressionTokenInteger",
+		"ExpressionTokenString",
+		"ExpressionTokenDate",
+		"ExpressionTokenTime",
+		"ExpressionTokenDateTime",
+		"ExpressionTokenBoolean",
+		"ExpressionTokenLiteral",
+		"ExpressionTokenDuration",
+		"ExpressionTokenGuid",
+		"ExpressionTokenAssignement",
+		"ExpressionTokenGeographyPolygon",
+		"ExpressionTokenGeometryPolygon",
+		"ExpressionTokenGeographyPoint",
+		"expressionTokenLast",
+	}[e]
+}
+
+// ExpressionParser is a ODATA expression parser.
+type ExpressionParser struct {
+	*Parser
+	ExpectBoolExpr bool       // Request expression to validate it is a boolean expression.
+	tokenizer      *Tokenizer // The expression tokenizer.
+}
+
+// ParseExpressionString converts a ODATA expression input string into a parse
+// tree that can be used by providers to create a response.
+// Expressions can be used within $filter and $orderby query options.
+func (p *ExpressionParser) ParseExpressionString(ctx context.Context, expression string) (*GoDataExpression, error) {
+	tokens, err := p.tokenizer.Tokenize(ctx, expression)
+	if err != nil {
+		return nil, err
+	}
+	// TODO: can we do this in one fell swoop?
+	postfix, err := p.InfixToPostfix(ctx, tokens)
+	if err != nil {
+		return nil, err
+	}
+	tree, err := p.PostfixToTree(ctx, postfix)
+	if err != nil {
+		return nil, err
+	}
+	if tree == nil || tree.Token == nil {
+		return nil, BadRequestError("Expression cannot be nil")
+	}
+	if p.ExpectBoolExpr && !p.isBooleanExpression(tree.Token) {
+		return nil, BadRequestError("Expression does not return a boolean value")
+	}
+	return &GoDataExpression{tree, expression}, nil
+}
+
+var GlobalExpressionTokenizer *Tokenizer
+var GlobalExpressionParser *ExpressionParser
+
+// init constructs single instances of Tokenizer and ExpressionParser and initializes their
+// respective packages variables.
+func init() {
+	p := NewExpressionParser()
+	t := p.tokenizer // use the Tokenizer instance created by
+
+	GlobalExpressionTokenizer = t
+	GlobalExpressionParser = p
+
+	GlobalFilterTokenizer = t
+	GlobalFilterParser = p
+}
+
+// ExpressionTokenizer creates a tokenizer capable of tokenizing ODATA expressions.
+// 4.01 Services MUST support case-insensitive operator names.
+// See https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#_Toc31360955
+func NewExpressionTokenizer() *Tokenizer {
+	t := Tokenizer{}
+	// guidValue = 8HEXDIG "-" 4HEXDIG "-" 4HEXDIG "-" 4HEXDIG "-" 12HEXDIG
+	t.Add(`^[[:xdigit:]]{8}-[[:xdigit:]]{4}-[[:xdigit:]]{4}-[[:xdigit:]]{4}-[[:xdigit:]]{12}`, ExpressionTokenGuid)
+	// duration      = [ "duration" ] SQUOTE durationValue SQUOTE
+	// durationValue = [ SIGN ] "P" [ 1*DIGIT "D" ] [ "T" [ 1*DIGIT "H" ] [ 1*DIGIT "M" ] [ 1*DIGIT [ "." 1*DIGIT ] "S" ] ]
+	// Duration literals in OData 4.0 required prefixing with “duration”.
+	// In OData 4.01, services MUST support duration and enumeration literals with or without the type prefix.
+	// OData clients that want to operate across OData 4.0 and OData 4.01 services should always include the prefix for duration and enumeration types.
+	t.Add(tokenDurationRe, ExpressionTokenDuration)
+	t.Add("^[0-9]{4,4}-[0-9]{2,2}-[0-9]{2,2}T[0-9]{2,2}:[0-9]{2,2}(:[0-9]{2,2}(.[0-9]+)?)?(Z|[+-][0-9]{2,2}:[0-9]{2,2})", ExpressionTokenDateTime)
+	t.Add("^-?[0-9]{4,4}-[0-9]{2,2}-[0-9]{2,2}", ExpressionTokenDate)
+	t.Add("^[0-9]{2,2}:[0-9]{2,2}(:[0-9]{2,2}(.[0-9]+)?)?", ExpressionTokenTime)
+	t.Add("^\\(", ExpressionTokenOpenParen)
+	t.Add("^\\)", ExpressionTokenCloseParen)
+	t.Add("^(?P<token>/)(?i)(any|all)", ExpressionTokenLambdaNav)                              // '/' as a token between a collection expression and a lambda function any() or all()
+	t.Add("^/", ExpressionTokenNav)                                                            // '/' as a token for property navigation.
+	t.Add("^=", ExpressionTokenAssignement)                                                    // '=' as a token for function argument assignment.
+	t.AddWithSubstituteFunc("^:", ExpressionTokenColon, func(in string) string { return "," }) // Function arg separator for lambda functions (any, all)
+	t.Add("^,", ExpressionTokenComma)                                                          // Default arg separator for functions
+	// Per ODATA ABNF grammar, functions must be followed by a open parenthesis.
+	// This implementation is a bit more lenient and allows space character between
+	// the function name and the open parenthesis.
+	// TODO: If we remove the optional space character, the function token will be
+	// mistakenly interpreted as a literal.
+	// E.g. ABNF for 'geo.distance':
+	// distanceMethodCallExpr   = "geo.distance"   OPEN BWS commonExpr BWS COMMA BWS commonExpr BWS CLOSE
+	t.Add("(?i)^(?P<token>(geo.distance|geo.intersects|geo.length))[\\s(]", ExpressionTokenFunc)
+	// Example: geography'POLYGON((-122.031577 47.578581, -122.031577 47.678581, -122.131577 47.678581))'
+	t.Add(`(?i)^geography'(?:SRID=(\d{1,5});)?POLYGON\s*\(\(\s*(?P<subtoken>-?\d+(\.\d+)?\s+-?\d+(\.\d+)?(?:\s*,\s*-?\d+(\.\d+)?\s+-?\d+(\.\d+)?)*?)\s*\)\)'`, ExpressionTokenGeographyPolygon)
+	t.Add(`(?i)^geometry'(?:SRID=(\d{1,5});)?POLYGON\s*\(\(\s*(?P<subtoken>-?\d+(\.\d+)?\s+-?\d+(\.\d+)?(?:\s*,\s*-?\d+(\.\d+)?\s+-?\d+(\.\d+)?)*?)\s*\)\)'`, ExpressionTokenGeometryPolygon)
+	// Example: geography'POINT(-122.131577 47.678581)'
+	t.Add(`(?i)^geography'POINT\s*\(\s*(?P<subtoken>-?\d+(\.\d+)?\s+-?\d+(\.\d+)?)\s*\)'`, ExpressionTokenGeographyPoint)
+	// According to ODATA ABNF notation, functions must be followed by a open parenthesis with no space
+	// between the function name and the open parenthesis.
+	// However, we are leniently allowing space characters between the function and the open parenthesis.
+	// TODO make leniency configurable.
+	// E.g. ABNF for 'indexof':
+	// indexOfMethodCallExpr    = "indexof"    OPEN BWS commonExpr BWS COMMA BWS commonExpr BWS CLOSE
+	t.Add("(?i)^(?P<token>(substringof|substring|length|indexof|exists|"+
+		"contains|endswith|startswith|tolower|toupper|trim|concat|year|month|day|"+
+		"hour|minute|second|fractionalseconds|date|time|totaloffsetminutes|now|"+
+		"maxdatetime|mindatetime|totalseconds|round|floor|ceiling|isof|cast))[\\s(]", ExpressionTokenFunc)
+	// Logical operators must be followed by a space character.
+	// However, in practice user have written requests such as not(City eq 'Seattle')
+	// We are leniently allowing space characters between the operator name and the open parenthesis.
+	// TODO make leniency configurable.
+	// Example:
+	// notExpr = "not" RWS boolCommonExpr
+	t.Add("(?i)^(?P<token>(eq|ne|gt|ge|lt|le|and|or|not|has|in))[\\s(]", ExpressionTokenLogical)
+	// Arithmetic operators must be followed by a space character.
+	t.Add("(?i)^(?P<token>(add|sub|mul|divby|div|mod))\\s", ExpressionTokenOp)
+	// anyExpr = "any" OPEN BWS [ lambdaVariableExpr BWS COLON BWS lambdaPredicateExpr ] BWS CLOSE
+	// allExpr = "all" OPEN BWS   lambdaVariableExpr BWS COLON BWS lambdaPredicateExpr   BWS CLOSE
+	t.Add("(?i)^(?P<token>(any|all))[\\s(]", ExpressionTokenLambda)
+	t.Add("(?i)^(?P<token>(case))[\\s(]", ExpressionTokenCase)
+	t.Add("^null", ExpressionTokenNull)
+	t.Add("^\\$it", ExpressionTokenIt)
+	t.Add("^\\$root", ExpressionTokenRoot)
+	t.Add("^-?[0-9]+\\.[0-9]+", ExpressionTokenFloat)
+	t.Add("^-?[0-9]+", ExpressionTokenInteger)
+	t.AddWithSubstituteFunc("^'(''|[^'])*'", ExpressionTokenString, unescapeTokenString)
+	t.Add("^(true|false)", ExpressionTokenBoolean)
+	t.AddWithSubstituteFunc("^@*[a-zA-Z][a-zA-Z0-9_.]*",
+		ExpressionTokenLiteral, unescapeUtfEncoding) // The optional '@' character is used to identify parameter aliases
+	t.Ignore("^ ", ExpressionTokenWhitespace)
+
+	return &t
+}
+
+// unescapeTokenString unescapes the input string according to the ODATA ABNF rules
+// and returns the unescaped string.
+// In ODATA ABNF, strings are encoded according to the following rules:
+// string           = SQUOTE *( SQUOTE-in-string / pchar-no-SQUOTE ) SQUOTE
+// SQUOTE-in-string = SQUOTE SQUOTE ; two consecutive single quotes represent one within a string literal
+// pchar-no-SQUOTE       = unreserved / pct-encoded-no-SQUOTE / other-delims / "$" / "&" / "=" / ":" / "@"
+// pct-encoded-no-SQUOTE = "%" ( "0" / "1" /   "3" / "4" / "5" / "6" / "8" / "9" / A-to-F ) HEXDIG
+// / "%" "2" ( "0" / "1" / "2" / "3" / "4" / "5" / "6" /   "8" / "9" / A-to-F )
+// unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
+//
+// See http://docs.oasis-open.org/odata/odata/v4.01/csprd03/abnf/odata-abnf-construction-rules.txt
+func unescapeTokenString(in string) string {
+	// The call to ReplaceAll() implements
+	// SQUOTE-in-string = SQUOTE SQUOTE ; two consecutive single quotes represent one within a string literal
+	if in == "''" {
+		return in
+	}
+	return strings.ReplaceAll(in, "''", "'")
+}
+
+// TODO: should we make this configurable?
+func unescapeUtfEncoding(in string) string {
+	return strings.ReplaceAll(in, "_x0020_", " ")
+}
+
+func NewExpressionParser() *ExpressionParser {
+	parser := &ExpressionParser{
+		Parser:         EmptyParser().WithLiteralToken(ExpressionTokenLiteral),
+		ExpectBoolExpr: false,
+		tokenizer:      NewExpressionTokenizer(),
+	}
+	parser.DefineOperator("/", 2, OpAssociationLeft, 8) // Note: '/' is used as a property navigator and between a collExpr and lambda function.
+	parser.DefineOperator("has", 2, OpAssociationLeft, 8)
+	// 'in' operator takes a literal list.
+	// City in ('Seattle') needs to be interpreted as a list expression, not a paren expression.
+	parser.DefineOperator("in", 2, OpAssociationLeft, 8).WithListExprPreference(true)
+	parser.DefineOperator("-", 1, OpAssociationNone, 7)
+	parser.DefineOperator("not", 1, OpAssociationRight, 7)
+	parser.DefineOperator("cast", 2, OpAssociationNone, 7)
+	parser.DefineOperator("mul", 2, OpAssociationNone, 6)
+	parser.DefineOperator("div", 2, OpAssociationNone, 6)   // Division
+	parser.DefineOperator("divby", 2, OpAssociationNone, 6) // Decimal Division
+	parser.DefineOperator("mod", 2, OpAssociationNone, 6)
+	parser.DefineOperator("add", 2, OpAssociationNone, 5)
+	parser.DefineOperator("sub", 2, OpAssociationNone, 5)
+	parser.DefineOperator("gt", 2, OpAssociationLeft, 4)
+	parser.DefineOperator("ge", 2, OpAssociationLeft, 4)
+	parser.DefineOperator("lt", 2, OpAssociationLeft, 4)
+	parser.DefineOperator("le", 2, OpAssociationLeft, 4)
+	parser.DefineOperator("eq", 2, OpAssociationLeft, 3)
+	parser.DefineOperator("ne", 2, OpAssociationLeft, 3)
+	parser.DefineOperator("and", 2, OpAssociationLeft, 2)
+	parser.DefineOperator("or", 2, OpAssociationLeft, 1)
+	parser.DefineOperator("=", 2, OpAssociationRight, 0) // Function argument assignment. E.g. MyFunc(Arg1='abc')
+	parser.DefineFunction("contains", []int{2}, true)
+	parser.DefineFunction("endswith", []int{2}, true)
+	parser.DefineFunction("startswith", []int{2}, true)
+	parser.DefineFunction("exists", []int{2}, true)
+	parser.DefineFunction("length", []int{1}, false)
+	parser.DefineFunction("indexof", []int{2}, false)
+	parser.DefineFunction("substring", []int{2, 3}, false)
+	parser.DefineFunction("substringof", []int{2}, false)
+	parser.DefineFunction("tolower", []int{1}, false)
+	parser.DefineFunction("toupper", []int{1}, false)
+	parser.DefineFunction("trim", []int{1}, false)
+	parser.DefineFunction("concat", []int{2}, false)
+	parser.DefineFunction("year", []int{1}, false)
+	parser.DefineFunction("month", []int{1}, false)
+	parser.DefineFunction("day", []int{1}, false)
+	parser.DefineFunction("hour", []int{1}, false)
+	parser.DefineFunction("minute", []int{1}, false)
+	parser.DefineFunction("second", []int{1}, false)
+	parser.DefineFunction("fractionalseconds", []int{1}, false)
+	parser.DefineFunction("date", []int{1}, false)
+	parser.DefineFunction("time", []int{1}, false)
+	parser.DefineFunction("totaloffsetminutes", []int{1}, false)
+	parser.DefineFunction("now", []int{0}, false)
+	parser.DefineFunction("maxdatetime", []int{0}, false)
+	parser.DefineFunction("mindatetime", []int{0}, false)
+	parser.DefineFunction("totalseconds", []int{1}, false)
+	parser.DefineFunction("round", []int{1}, false)
+	parser.DefineFunction("floor", []int{1}, false)
+	parser.DefineFunction("ceiling", []int{1}, false)
+	parser.DefineFunction("isof", []int{1, 2}, true) // isof function can take one or two arguments.
+	parser.DefineFunction("cast", []int{2}, false)
+	parser.DefineFunction("geo.distance", []int{2}, false)
+	// The geo.intersects function has the following signatures:
+	//   Edm.Boolean geo.intersects(Edm.GeographyPoint,Edm.GeographyPolygon)
+	//   Edm.Boolean geo.intersects(Edm.GeometryPoint,Edm.GeometryPolygon)
+	// The geo.intersects function returns true if the specified point lies within the interior
+	// or on the boundary of the specified polygon, otherwise it returns false.
+	parser.DefineFunction("geo.intersects", []int{2}, true)
+	// The geo.length function has the following signatures:
+	//   Edm.Double geo.length(Edm.GeographyLineString)
+	//   Edm.Double geo.length(Edm.GeometryLineString)
+	// The geo.length function returns the total length of its line string parameter
+	// in the coordinate reference system signified by its SRID.
+	parser.DefineFunction("geo.length", []int{1}, false)
+	// 'any' can take either zero or two arguments with the later having the form any(d:d/Prop eq 1).
+	// Godata interprets the colon as an argument delimiter and considers the function to have two arguments.
+	parser.DefineFunction("any", []int{0, 2}, true)
+	// 'all' requires two arguments of a form similar to 'any'.
+	parser.DefineFunction("all", []int{2}, true)
+	// Define 'case' as a function accepting 1-10 arguments. Each argument is a pair of expressions separated by a colon.
+	// See https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_case
+	parser.DefineFunction("case", []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, true)
+
+	return parser
+}
+
+func (p *ExpressionParser) SemanticizeExpression(
+	expression *GoDataExpression,
+	service *GoDataService,
+	entity *GoDataEntityType,
+) error {
+
+	if expression == nil || expression.Tree == nil {
+		return nil
+	}
+
+	var semanticizeExpressionNode func(node *ParseNode) error
+	semanticizeExpressionNode = func(node *ParseNode) error {
+
+		if node.Token.Type == ExpressionTokenLiteral {
+			prop, ok := service.PropertyLookup[entity][node.Token.Value]
+			if !ok {
+				return BadRequestError("No property found " + node.Token.Value + " on entity " + entity.Name)
+			}
+			node.Token.SemanticType = SemanticTypeProperty
+			node.Token.SemanticReference = prop
+		} else {
+			node.Token.SemanticType = SemanticTypePropertyValue
+			node.Token.SemanticReference = &node.Token.Value
+		}
+
+		for _, child := range node.Children {
+			err := semanticizeExpressionNode(child)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+
+	return semanticizeExpressionNode(expression.Tree)
+}
@@ -0,0 +1,66 @@
+package godata
+
+import "context"
+
+var GlobalFilterTokenizer *Tokenizer
+var GlobalFilterParser *ExpressionParser
+
+// ParseFilterString converts an input string from the $filter part of the URL into a parse
+// tree that can be used by providers to create a response.
+func ParseFilterString(ctx context.Context, filter string) (*GoDataFilterQuery, error) {
+	tokens, err := GlobalFilterTokenizer.Tokenize(ctx, filter)
+	if err != nil {
+		return nil, err
+	}
+	// TODO: can we do this in one fell swoop?
+	postfix, err := GlobalFilterParser.InfixToPostfix(ctx, tokens)
+	if err != nil {
+		return nil, err
+	}
+	tree, err := GlobalFilterParser.PostfixToTree(ctx, postfix)
+	if err != nil {
+		return nil, err
+	}
+	if tree == nil || tree.Token == nil || !GlobalFilterParser.isBooleanExpression(tree.Token) {
+		return nil, BadRequestError("Value must be a boolean expression")
+	}
+	return &GoDataFilterQuery{tree, filter}, nil
+}
+
+func SemanticizeFilterQuery(
+	filter *GoDataFilterQuery,
+	service *GoDataService,
+	entity *GoDataEntityType,
+) error {
+
+	if filter == nil || filter.Tree == nil {
+		return nil
+	}
+
+	var semanticizeFilterNode func(node *ParseNode) error
+	semanticizeFilterNode = func(node *ParseNode) error {
+
+		if node.Token.Type == ExpressionTokenLiteral {
+			prop, ok := service.PropertyLookup[entity][node.Token.Value]
+			if !ok {
+				return BadRequestError("No property found " + node.Token.Value + " on entity " + entity.Name)
+			}
+			node.Token.SemanticType = SemanticTypeProperty
+			node.Token.SemanticReference = prop
+		} else {
+			node.Token.SemanticType = SemanticTypePropertyValue
+			node.Token.SemanticReference = &node.Token.Value
+		}
+
+		for _, child := range node.Children {
+			err := semanticizeFilterNode(child)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+
+	return semanticizeFilterNode(filter.Tree)
+}
@@ -0,0 +1,19 @@
+package godata
+
+import "context"
+
+const (
+	ALLPAGES = "allpages"
+	NONE     = "none"
+)
+
+func ParseInlineCountString(ctx context.Context, inlinecount string) (*GoDataInlineCountQuery, error) {
+	result := GoDataInlineCountQuery(inlinecount)
+	if inlinecount == ALLPAGES {
+		return &result, nil
+	} else if inlinecount == NONE {
+		return &result, nil
+	} else {
+		return nil, BadRequestError("Invalid inlinecount query.")
+	}
+}
@@ -0,0 +1,277 @@
+package godata
+
+import (
+	"encoding/xml"
+)
+
+const (
+	GoDataString         = "Edm.String"
+	GoDataInt16          = "Edm.Int16"
+	GoDataInt32          = "Edm.Int32"
+	GoDataInt64          = "Edm.Int64"
+	GoDataDecimal        = "Edm.Decimal"
+	GoDataBinary         = "Edm.Binary"
+	GoDataBoolean        = "Edm.Boolean"
+	GoDataTimeOfDay      = "Edm.TimeOfDay"
+	GoDataDate           = "Edm.Date"
+	GoDataDateTimeOffset = "Edm.DateTimeOffset"
+)
+
+type GoDataMetadata struct {
+	XMLName      xml.Name `xml:"edmx:Edmx"`
+	XMLNamespace string   `xml:"xmlns:edmx,attr"`
+	Version      string   `xml:"Version,attr"`
+	DataServices *GoDataServices
+	References   []*GoDataReference
+}
+
+func (t *GoDataMetadata) Bytes() ([]byte, error) {
+	output, err := xml.MarshalIndent(t, "", "    ")
+	if err != nil {
+		return nil, err
+	}
+
+	return append([]byte(xml.Header), output...), nil
+}
+
+func (t *GoDataMetadata) String() string {
+	return ""
+}
+
+type GoDataReference struct {
+	XMLName            xml.Name `xml:"edmx:Reference"`
+	Uri                string   `xml:"Uri,attr"`
+	Includes           []*GoDataInclude
+	IncludeAnnotations []*GoDataIncludeAnnotations
+}
+
+type GoDataInclude struct {
+	XMLName   xml.Name `xml:"edmx:Include"`
+	Namespace string   `xml:"Namespace,attr"`
+	Alias     string   `xml:"Alias,attr,omitempty"`
+}
+
+type GoDataIncludeAnnotations struct {
+	XMLName         xml.Name `xml:"edmx:IncludeAnnotations"`
+	TermNamespace   string   `xml:"TermNamespace,attr"`
+	Qualifier       string   `xml:"Qualifier,attr,omitempty"`
+	TargetNamespace string   `xml:"TargetNamespace,attr,omitempty"`
+}
+
+type GoDataServices struct {
+	XMLName xml.Name `xml:"edmx:DataServices"`
+	Schemas []*GoDataSchema
+}
+
+type GoDataSchema struct {
+	XMLName          xml.Name `xml:"Schema"`
+	Namespace        string   `xml:"Namespace,attr"`
+	Alias            string   `xml:"Alias,attr,omitempty"`
+	Actions          []*GoDataAction
+	Annotations      []*GoDataAnnotations
+	Annotation       []*GoDataAnnotation
+	ComplexTypes     []*GoDataComplexType
+	EntityContainers []*GoDataEntityContainer
+	EntityTypes      []*GoDataEntityType
+	EnumTypes        []*GoDataEnumType
+	Functions        []*GoDataFunction
+	Terms            []*GoDataTerm
+	TypeDefinitions  []*GoDataTypeDefinition
+}
+
+type GoDataAction struct {
+	XMLName       xml.Name `xml:"Action"`
+	Name          string   `xml:"Name,attr"`
+	IsBound       string   `xml:"IsBound,attr,omitempty"`
+	EntitySetPath string   `xml:"EntitySetPath,attr,omitempty"`
+	Parameters    []*GoDataParameter
+	ReturnType    *GoDataReturnType
+}
+
+type GoDataAnnotations struct {
+	XMLName     xml.Name `xml:"Annotations"`
+	Target      string   `xml:"Target,attr"`
+	Qualifier   string   `xml:"Qualifier,attr,omitempty"`
+	Annotations []*GoDataAnnotation
+}
+
+type GoDataAnnotation struct {
+	XMLName   xml.Name `xml:"Annotation"`
+	Term      string   `xml:"Term,attr"`
+	Qualifier string   `xml:"Qualifier,attr,omitempty"`
+}
+
+type GoDataComplexType struct {
+	XMLName              xml.Name `xml:"ComplexType"`
+	Name                 string   `xml:"Name,attr"`
+	BaseType             string   `xml:"BaseType,attr,omitempty"`
+	Abstract             string   `xml:"Abstract,attr,omitempty"`
+	OpenType             string   `xml:"OpenType,attr,omitempty"`
+	Properties           []*GoDataProperty
+	NavigationProperties []*GoDataNavigationProperty
+}
+
+type GoDataEntityContainer struct {
+	XMLName         xml.Name `xml:"EntityContainer"`
+	Name            string   `xml:"Name,attr"`
+	Extends         string   `xml:"Extends,attr,omitempty"`
+	EntitySets      []*GoDataEntitySet
+	Singletons      []*GoDataSingleton
+	ActionImports   []*GoDataActionImport
+	FunctionImports []*GoDataFunctionImport
+}
+
+type GoDataEntityType struct {
+	XMLName              xml.Name `xml:"EntityType"`
+	Name                 string   `xml:"Name,attr"`
+	BaseType             string   `xml:"BaseType,attr,omitempty"`
+	Abstract             string   `xml:"Abstract,attr,omitempty"`
+	OpenType             string   `xml:"OpenType,attr,omitempty"`
+	HasStream            string   `xml:"HasStream,attr,omitempty"`
+	Key                  *GoDataKey
+	Properties           []*GoDataProperty
+	NavigationProperties []*GoDataNavigationProperty
+}
+
+type GoDataEnumType struct {
+	XMLName        xml.Name `xml:"EnumType"`
+	Name           string   `xml:"Name,attr"`
+	UnderlyingType string   `xml:"UnderlyingType,attr,omitempty"`
+	IsFlags        string   `xml:"IsFlags,attr,omitempty"`
+	Members        []*GoDataMember
+}
+
+type GoDataFunction struct {
+	XMLName       xml.Name `xml:"Function"`
+	Name          string   `xml:"Name,attr"`
+	IsBound       string   `xml:"IsBound,attr,omitempty"`
+	IsComposable  string   `xml:"IsComposable,attr,omitempty"`
+	EntitySetPath string   `xml:"EntitySetPath,attr,omitempty"`
+	Parameters    []*GoDataParameter
+	ReturnType    *GoDataReturnType
+}
+
+type GoDataTypeDefinition struct {
+	XMLName        xml.Name `xml:"TypeDefinition"`
+	Name           string   `xml:"Name,attr"`
+	UnderlyingType string   `xml:"UnderlyingTypeattr,omitempty"`
+	Annotations    []*GoDataAnnotation
+}
+
+type GoDataProperty struct {
+	XMLName      xml.Name `xml:"Property"`
+	Name         string   `xml:"Name,attr"`
+	Type         string   `xml:"Type,attr"`
+	Nullable     string   `xml:"Nullable,attr,omitempty"`
+	MaxLength    int      `xml:"MaxLength,attr,omitempty"`
+	Precision    int      `xml:"Precision,attr,omitempty"`
+	Scale        int      `xml:"Scale,attr,omitempty"`
+	Unicode      string   `xml:"Unicode,attr,omitempty"`
+	SRID         string   `xml:"SRID,attr,omitempty"`
+	DefaultValue string   `xml:"DefaultValue,attr,omitempty"`
+}
+
+type GoDataNavigationProperty struct {
+	XMLName                xml.Name `xml:"NavigationProperty"`
+	Name                   string   `xml:"Name,attr"`
+	Type                   string   `xml:"Type,attr"`
+	Nullable               string   `xml:"Nullable,attr,omitempty"`
+	Partner                string   `xml:"Partner,attr,omitempty"`
+	ContainsTarget         string   `xml:"ContainsTarget,attr,omitempty"`
+	ReferentialConstraints []*GoDataReferentialConstraint
+}
+
+type GoDataReferentialConstraint struct {
+	XMLName            xml.Name        `xml:"ReferentialConstraint"`
+	Property           string          `xml:"Property,attr"`
+	ReferencedProperty string          `xml:"ReferencedProperty,attr"`
+	OnDelete           *GoDataOnDelete `xml:"OnDelete,omitempty"`
+}
+
+type GoDataOnDelete struct {
+	XMLName xml.Name `xml:"OnDelete"`
+	Action  string   `xml:"Action,attr"`
+}
+
+type GoDataEntitySet struct {
+	XMLName                    xml.Name `xml:"EntitySet"`
+	Name                       string   `xml:"Name,attr"`
+	EntityType                 string   `xml:"EntityType,attr"`
+	IncludeInServiceDocument   string   `xml:"IncludeInServiceDocument,attr,omitempty"`
+	NavigationPropertyBindings []*GoDataNavigationPropertyBinding
+}
+
+type GoDataSingleton struct {
+	XMLName                    xml.Name `xml:"Singleton"`
+	Name                       string   `xml:"Name,attr"`
+	Type                       string   `xml:"Type,attr"`
+	NavigationPropertyBindings []*GoDataNavigationPropertyBinding
+}
+
+type GoDataNavigationPropertyBinding struct {
+	XMLName xml.Name `xml:"NavigationPropertyBinding"`
+	Path    string   `xml:"Path,attr"`
+	Target  string   `xml:"Target,attr"`
+}
+
+type GoDataActionImport struct {
+	XMLName   xml.Name `xml:"ActionImport"`
+	Name      string   `xml:"Name,attr"`
+	Action    string   `xml:"Action,attr"`
+	EntitySet string   `xml:"EntitySet,attr,omitempty"`
+}
+
+type GoDataFunctionImport struct {
+	XMLName                  xml.Name `xml:"FunctionImport"`
+	Name                     string   `xml:"Name,attr"`
+	Function                 string   `xml:"Function,attr"`
+	EntitySet                string   `xml:"EntitySet,attr,omitempty"`
+	IncludeInServiceDocument string   `xml:"IncludeInServiceDocument,attr,omitempty"`
+}
+
+type GoDataKey struct {
+	XMLName     xml.Name `xml:"Key"`
+	PropertyRef *GoDataPropertyRef
+}
+
+type GoDataPropertyRef struct {
+	XMLName xml.Name `xml:"PropertyRef"`
+	Name    string   `xml:"Name,attr"`
+}
+
+type GoDataParameter struct {
+	XMLName   xml.Name `xml:"Parameter"`
+	Name      string   `xml:"Name,attr"`
+	Type      string   `xml:"Type,attr"`
+	Nullable  string   `xml:"Nullable,attr,omitempty"`
+	MaxLength int      `xml:"MaxLength,attr,omitempty"`
+	Precision int      `xml:"Precision,attr,omitempty"`
+	Scale     int      `xml:"Scale,attr,omitempty"`
+	SRID      string   `xml:"SRID,attr,omitempty"`
+}
+
+type GoDataReturnType struct {
+	XMLName   xml.Name `xml:"ReturnType"`
+	Name      string   `xml:"Name,attr"`
+	Type      string   `xml:"Type,attr"`
+	Nullable  string   `xml:"Nullable,attr,omitempty"`
+	MaxLength int      `xml:"MaxLength,attr,omitempty"`
+	Precision int      `xml:"Precision,attr,omitempty"`
+	Scale     int      `xml:"Scale,attr,omitempty"`
+	SRID      string   `xml:"SRID,attr,omitempty"`
+}
+
+type GoDataMember struct {
+	XMLName xml.Name `xml:"Member"`
+	Name    string   `xml:"Name,attr"`
+	Value   string   `xml:"Value,attr,omitempty"`
+}
+
+type GoDataTerm struct {
+	XMLName      xml.Name `xml:"Term"`
+	Name         string   `xml:"Name,attr"`
+	Type         string   `xml:"Type,attr"`
+	BaseTerm     string   `xml:"BaseTerm,attr,omitempty"`
+	DefaultValue string   `xml:"DefaultValue,attr,omitempty"`
+	AppliesTo    string   `xml:"AppliesTo,attr,omitempty"`
+}
@@ -0,0 +1,102 @@
+package godata
+
+import (
+	"context"
+	"strings"
+)
+
+const (
+	ASC  = "asc"
+	DESC = "desc"
+)
+
+type OrderByItem struct {
+	Field *Token            // The raw value of the orderby field or expression.
+	Tree  *GoDataExpression // The orderby expression parsed as a tree.
+	Order string            // Ascending or descending order.
+}
+
+func ParseOrderByString(ctx context.Context, orderby string) (*GoDataOrderByQuery, error) {
+	return GlobalExpressionParser.ParseOrderByString(ctx, orderby)
+}
+
+// The value of the $orderby System Query option contains a comma-separated
+// list of expressions whose primitive result values are used to sort the items.
+// The service MUST order by the specified property in ascending order.
+// 4.01 services MUST support case-insensitive values for asc and desc.
+func (p *ExpressionParser) ParseOrderByString(ctx context.Context, orderby string) (*GoDataOrderByQuery, error) {
+	items := strings.Split(orderby, ",")
+
+	result := make([]*OrderByItem, 0)
+
+	for _, v := range items {
+		v = strings.TrimSpace(v)
+
+		cfg, hasComplianceConfig := ctx.Value(odataCompliance).(OdataComplianceConfig)
+		if !hasComplianceConfig {
+			// Strict ODATA compliance by default.
+			cfg = ComplianceStrict
+		}
+
+		if len(v) == 0 && cfg&ComplianceIgnoreInvalidComma == 0 {
+			return nil, BadRequestError("Extra comma in $orderby.")
+		}
+
+		var order string
+		vLower := strings.ToLower(v)
+		if strings.HasSuffix(vLower, " "+ASC) {
+			order = ASC
+		} else if strings.HasSuffix(vLower, " "+DESC) {
+			order = DESC
+		}
+		if order == "" {
+			order = ASC // default order
+		} else {
+			v = v[:len(v)-len(order)]
+			v = strings.TrimSpace(v)
+		}
+
+		if tree, err := p.ParseExpressionString(ctx, v); err != nil {
+			switch e := err.(type) {
+			case *GoDataError:
+				return nil, &GoDataError{
+					ResponseCode: e.ResponseCode,
+					Message:      "Invalid $orderby query option",
+					Cause:        e,
+				}
+			default:
+				return nil, &GoDataError{
+					ResponseCode: 500,
+					Message:      "Invalid $orderby query option",
+					Cause:        e,
+				}
+			}
+		} else {
+			result = append(result, &OrderByItem{
+				Field: &Token{Value: unescapeUtfEncoding(v)},
+				Tree:  tree,
+				Order: order,
+			})
+
+		}
+	}
+
+	return &GoDataOrderByQuery{result, orderby}, nil
+}
+
+func SemanticizeOrderByQuery(orderby *GoDataOrderByQuery, service *GoDataService, entity *GoDataEntityType) error {
+	if orderby == nil {
+		return nil
+	}
+
+	for _, item := range orderby.OrderByItems {
+		if prop, ok := service.PropertyLookup[entity][item.Field.Value]; ok {
+			item.Field.SemanticType = SemanticTypeProperty
+			item.Field.SemanticReference = prop
+		} else {
+			return BadRequestError("No property " + item.Field.Value + " for entity " + entity.Name)
+		}
+	}
+
+	return nil
+}
@@ -0,0 +1,916 @@
+package godata
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+const (
+	OpAssociationLeft int = iota
+	OpAssociationRight
+	OpAssociationNone
+)
+
+const (
+	TokenListExpr = "list"
+
+	// TokenComma is the default separator for function arguments.
+	TokenComma      = ","
+	TokenOpenParen  = "("
+	TokenCloseParen = ")"
+)
+
+type Tokenizer struct {
+	TokenMatchers  []*TokenMatcher
+	IgnoreMatchers []*TokenMatcher
+}
+
+type TokenMatcher struct {
+	Pattern         string                 // The regular expression matching a ODATA query token, such as literal value, operator or function
+	Re              *regexp.Regexp         // The compiled regex
+	Token           TokenType              // The token identifier
+	CaseInsensitive bool                   // Regex is case-insensitive
+	Subst           func(in string) string // A function that substitutes the raw input token with another representation. By default it is the identity.
+}
+
+// TokenType is the interface that must be implemented by all token types.
+type TokenType interface {
+	Value() int
+}
+
+type ListExprToken int
+
+func (l ListExprToken) Value() int {
+	return (int)(l)
+}
+
+func (l ListExprToken) String() string {
+	return [...]string{
+		"TokenTypeListExpr",
+		"TokenTypeArgCount",
+	}[l]
+}
+
+const (
+	// TokenTypeListExpr represents a parent node for a variadic listExpr.
+	// "list"
+	//   "item1"
+	//   "item2"
+	//   ...
+	TokenTypeListExpr ListExprToken = iota
+	// TokenTypeArgCount is used to specify the number of arguments of a function or listExpr
+	// This is used to handle variadic functions and listExpr.
+	TokenTypeArgCount
+)
+
+type Token struct {
+	Value string
+	Type  TokenType
+	// Holds information about the semantic meaning of this token taken from the
+	// context of the GoDataService.
+	SemanticType      SemanticType
+	SemanticReference interface{}
+}
+
+func (t *Tokenizer) Add(pattern string, token TokenType) {
+	t.AddWithSubstituteFunc(pattern, token, func(in string) string { return in })
+}
+
+func (t *Tokenizer) AddWithSubstituteFunc(pattern string, token TokenType, subst func(string) string) {
+	matcher := createTokenMatcher(pattern, token, subst)
+	t.TokenMatchers = append(t.TokenMatchers, matcher)
+}
+
+func createTokenMatcher(pattern string, token TokenType, subst func(string) string) *TokenMatcher {
+	rxp := regexp.MustCompile(pattern)
+	return &TokenMatcher{
+		Pattern:         pattern,
+		Re:              rxp,
+		Token:           token,
+		CaseInsensitive: strings.Contains(pattern, "(?i)"),
+		Subst:           subst,
+	}
+}
+
+func (t *Tokenizer) Ignore(pattern string, token TokenType) {
+	rxp := regexp.MustCompile(pattern)
+	matcher := &TokenMatcher{
+		Pattern:         pattern,
+		Re:              rxp,
+		Token:           token,
+		CaseInsensitive: strings.Contains(pattern, "(?i)"),
+		Subst:           func(in string) string { return in },
+	}
+	t.IgnoreMatchers = append(t.IgnoreMatchers, matcher)
+}
+
+// TokenizeBytes takes the input byte array and returns an array of tokens.
+// Return an empty array if there are no tokens.
+func (t *Tokenizer) TokenizeBytes(ctx context.Context, target []byte) ([]*Token, error) {
+	result := make([]*Token, 0)
+	match := true // false when no match is found
+	for len(target) > 0 && match {
+		match = false
+		ignore := false
+		var tokens [][]byte
+		var m *TokenMatcher
+		for _, m = range t.TokenMatchers {
+			tokens = m.Re.FindSubmatch(target)
+			if len(tokens) > 0 {
+				match = true
+				break
+			}
+		}
+		if len(tokens) == 0 {
+			for _, m = range t.IgnoreMatchers {
+				tokens = m.Re.FindSubmatch(target)
+				if len(tokens) > 0 {
+					ignore = true
+					break
+				}
+			}
+		}
+		if len(tokens) > 0 {
+			match = true
+			var parsed Token
+			var token []byte
+			// If the regex includes a named group and the name of that group is "token"
+			// then the value of the token is set to the subgroup. Other characters are
+			// not consumed by the tokenization process.
+			// For example, the regex:
+			//    ^(?P<token>(eq|ne|gt|ge|lt|le|and|or|not|has|in))\\s
+			// has a group named 'token' and the group is followed by a mandatory space character.
+			// If the input data is `Name eq 'Bob'`, the token is correctly set to 'eq' and
+			// the space after eq is not consumed, because the space character itself is supposed
+			// to be the next token.
+			//
+			// If Token.Value needs to be a sub-regex but the entire token needs to be consumed,
+			// use 'subtoken'
+			//    ^(duration)?'(?P<subtoken>[0-9])'
+			l := 0
+			if idx := m.Re.SubexpIndex("token"); idx > 0 {
+				token = tokens[idx]
+				l = len(token)
+			} else if idx := m.Re.SubexpIndex("subtoken"); idx > 0 {
+				token = tokens[idx]
+				l = len(tokens[0])
+			} else {
+				token = tokens[0]
+				l = len(token)
+			}
+			target = target[l:] // remove the token from the input
+			if !ignore {
+				var v string
+				if m.CaseInsensitive {
+					// In ODATA 4.0.1, operators and functions are case insensitive.
+					v = strings.ToLower(string(token))
+				} else {
+					v = string(token)
+				}
+				parsed = Token{
+					Value: m.Subst(v),
+					Type:  m.Token,
+				}
+				result = append(result, &parsed)
+			}
+		}
+	}
+
+	if len(target) > 0 && !match {
+		return result, BadRequestError(fmt.Sprintf("Token '%s' is invalid", string(target)))
+	}
+	if len(result) < 1 {
+		return result, BadRequestError("Empty query parameter")
+	}
+	return result, nil
+}
+
+func (t *Tokenizer) Tokenize(ctx context.Context, target string) ([]*Token, error) {
+	return t.TokenizeBytes(ctx, []byte(target))
+}
+
+type TokenHandler func(token *Token, stack tokenStack) error
+
+type Parser struct {
+	// Map from string inputs to operator types
+	Operators map[string]*Operator
+	// Map from string inputs to function types
+	Functions map[string]*Function
+
+	LiteralToken TokenType
+}
+
+type Operator struct {
+	Token string
+	// Whether the operator is left/right/or not associative.
+	// Determines how operators of the same precedence are grouped in the absence of parentheses.
+	Association int
+	// The number of operands this operator operates on
+	Operands int
+	// Rank of precedence. A higher value indicates higher precedence.
+	Precedence int
+	// Determine if the operands should be interpreted as a ListExpr or parenExpr according
+	// to ODATA ABNF grammar.
+	// This is only used when a listExpr has zero or one items.
+	// When a listExpr has 2 or more items, there is no ambiguity between listExpr and parenExpr.
+	// For example:
+	//    2 + (3) ==> the right operand is a parenExpr.
+	//    City IN ('Seattle', 'Atlanta') ==> the right operand is unambiguously a listExpr.
+	//    City IN ('Seattle') ==> the right operand should be a listExpr.
+	PreferListExpr bool
+}
+
+func (o *Operator) WithListExprPreference(v bool) *Operator {
+	o.PreferListExpr = v
+	return o
+}
+
+type Function struct {
+	Token  string // The function token
+	Params []int  // The number of parameters this function accepts
+	ReturnsBool bool // Indicates if the function has a boolean return value
+}
+
+type ParseNode struct {
+	Token    *Token
+	Parent   *ParseNode
+	Children []*ParseNode
+}
+
+func (p *ParseNode) String() string {
+	var sb strings.Builder
+	var treePrinter func(n *ParseNode, sb *strings.Builder, level int, idx *int)
+
+	treePrinter = func(n *ParseNode, s *strings.Builder, level int, idx *int) {
+		if n == nil || n.Token == nil {
+			s.WriteRune('\n')
+			return
+		}
+		s.WriteString(fmt.Sprintf("[%2d][%2d]", *idx, n.Token.Type))
+		*idx += 1
+		s.WriteString(strings.Repeat("  ", level))
+		s.WriteString(n.Token.Value)
+		s.WriteRune('\n')
+		for _, v := range n.Children {
+			treePrinter(v, s, level+1, idx)
+		}
+	}
+	idx := 0
+	treePrinter(p, &sb, 0, &idx)
+	return sb.String()
+}
+
+func EmptyParser() *Parser {
+	return &Parser{
+		Operators:    make(map[string]*Operator),
+		Functions:    make(map[string]*Function),
+		LiteralToken: nil,
+	}
+}
+
+func (p *Parser) WithLiteralToken(token TokenType) *Parser {
+	p.LiteralToken = token
+	return p
+}
+
+// DefineOperator adds an operator to the language.
+// Provide the token, the expected number of arguments,
+// whether the operator is left, right, or not associative, and a precedence.
+func (p *Parser) DefineOperator(token string, operands, assoc, precedence int) *Operator {
+	op := &Operator{
+		Token:       token,
+		Association: assoc,
+		Operands:    operands,
+		Precedence:  precedence,
+	}
+	p.Operators[token] = op
+	return op
+}
+
+// DefineFunction adds a function to the language.
+// - params is the number of parameters this function accepts
+// - returnsBool indicates if the function has a boolean return value
+func (p *Parser) DefineFunction(token string, params []int, returnsBool bool) *Function {
+	sort.Sort(sort.Reverse(sort.IntSlice(params)))
+	f := &Function{token, params, returnsBool}
+	p.Functions[token] = f
+	return f
+}
+
+// CustomFunctionInput serves as input to function DefineCustomFunctions()
+type CustomFunctionInput struct {
+	Name      string // case-insensitive function name
+	NumParams []int  // number of allowed parameters
+	ReturnsBool bool // indicates if the function has a boolean return value
+}
+
+// DefineCustomFunctions introduces additional function names to be considered as legal function
+// names while parsing. The function names must be different from all canonical functions and
+// operators defined in the odata specification.
+//
+// See https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_Functions
+func DefineCustomFunctions(functions []CustomFunctionInput) error {
+	var funcNames []string
+	for _, v := range functions {
+		name := strings.ToLower(v.Name)
+
+		if GlobalExpressionParser.Functions[name] != nil {
+			return fmt.Errorf("custom function '%s' may not override odata canonical function", name)
+		} else if GlobalExpressionParser.Operators[name] != nil {
+			return fmt.Errorf("custom function '%s' may not override odata operator", name)
+		}
+
+		GlobalExpressionParser.DefineFunction(name, v.NumParams, v.ReturnsBool)
+		funcNames = append(funcNames, name)
+	}
+
+	// create a regex that performs a case-insensitive match of any one of the provided function names
+	pattern := fmt.Sprintf("(?i)^(?P<token>(%s))[\\s(]", strings.Join(funcNames, "|"))
+	matcher := createTokenMatcher(pattern, ExpressionTokenFunc, func(in string) string { return in })
+
+	// The tokenizer has a list of matcher expressions which are evaluated in order while parsing
+	// with the first matching rule being applied. The matcher for custom functions is inserted
+	// immediately following the matcher for functions defined in the Odata specification (identified
+	// by finding rule with type ExpressionTokenFunc). Because the rules are applied in order based
+	// on specificity, inserting at this location ensures the custom function rule has similar
+	// precedence as functioned defined the Odata specification.
+	list := GlobalExpressionTokenizer.TokenMatchers
+	for i, v := range GlobalExpressionTokenizer.TokenMatchers {
+		if v.Token == ExpressionTokenFunc {
+			list = append(list[:i+1], list[i:]...)
+			list[i] = matcher
+			GlobalExpressionTokenizer.TokenMatchers = list
+			return nil
+		}
+	}
+
+	// This is a godata package bug. The tokenizer should define matches for the token
+	// type ExpressionTokenFunc for functions defined in the Odata specification.
+	// Such as substring and tolower.
+	return errors.New("godata parser is missing function matchers")
+}
+
+func (p *Parser) isFunction(token *Token) bool {
+	_, ok := p.Functions[token.Value]
+	return ok
+}
+
+func (p *Parser) isOperator(token *Token) bool {
+	_, ok := p.Operators[token.Value]
+	return ok
+}
+
+// isBooleanExpression returns True when the expression token 't' has a resulting boolean value
+func (p *Parser) isBooleanExpression(t *Token) bool {
+	switch t.Type {
+	case ExpressionTokenBoolean:
+		// Valid boolean expression
+	case ExpressionTokenLogical:
+		// eq|ne|gt|ge|lt|le|and|or|not|has|in
+		// Valid boolean expression
+	case ExpressionTokenFunc:
+		// Depends on function return type
+		f := p.Functions[t.Value]
+		if !f.ReturnsBool {
+			return false
+		}
+	case ExpressionTokenLambdaNav:
+		// Lambda Navigation.
+		// Valid boolean expression
+	default:
+		return false
+	}
+	return true
+}
+
+// InfixToPostfix parses the input string of tokens using the given definitions of operators
+// and functions.
+// Everything else is assumed to be a literal.
+// Uses the Shunting-Yard algorithm.
+//
+// Infix notation for variadic functions and operators: f ( a, b, c, d )
+// Postfix notation with wall notation:                 | a b c d f
+// Postfix notation with count notation:                a b c d 4 f
+func (p *Parser) InfixToPostfix(ctx context.Context, tokens []*Token) (*tokenQueue, error) {
+	queue := tokenQueue{} // output queue in postfix
+	stack := tokenStack{} // Operator stack
+
+	previousTokenIsLiteral := false
+	var previousToken *Token = nil
+
+	incrementListArgCount := func(token *Token) {
+		if !stack.Empty() {
+			if previousToken != nil && previousToken.Value == TokenOpenParen {
+				stack.Head.listArgCount++
+			} else if stack.Head.Token.Value == TokenOpenParen {
+				stack.Head.listArgCount++
+			}
+		}
+	}
+	cfg, hasComplianceConfig := ctx.Value(odataCompliance).(OdataComplianceConfig)
+	if !hasComplianceConfig {
+		// Strict ODATA compliance by default.
+		cfg = ComplianceStrict
+	}
+	for len(tokens) > 0 {
+		token := tokens[0]
+		tokens = tokens[1:]
+		switch {
+		case p.isFunction(token):
+			previousTokenIsLiteral = false
+			if len(tokens) == 0 || tokens[0].Value != TokenOpenParen {
+				// A function token must be followed by open parenthesis token.
+				return nil, BadRequestError(fmt.Sprintf("Function '%s' must be followed by '('", token.Value))
+			}
+			incrementListArgCount(token)
+			// push functions onto the stack
+			stack.Push(token)
+		case p.isOperator(token):
+			previousTokenIsLiteral = false
+			// push operators onto stack according to precedence
+			o1 := p.Operators[token.Value]
+			if !stack.Empty() {
+				for o2, ok := p.Operators[stack.Peek().Value]; ok &&
+					((o1.Association == OpAssociationLeft && o1.Precedence <= o2.Precedence) ||
+						(o1.Association == OpAssociationRight && o1.Precedence < o2.Precedence)); {
+					queue.Enqueue(stack.Pop())
+
+					if stack.Empty() {
+						break
+					}
+					o2, ok = p.Operators[stack.Peek().Value]
+				}
+			}
+			if o1.Operands == 1 { // not, -
+				incrementListArgCount(token)
+			}
+			stack.Push(token)
+		case token.Value == TokenOpenParen:
+			previousTokenIsLiteral = false
+			// In OData, the parenthesis tokens can be used:
+			// - As a parenExpr to set explicit precedence order, such as "(a + 2) x b"
+			//   These precedence tokens are removed while parsing the OData query.
+			// - As a listExpr for multi-value sets, such as "City in ('San Jose', 'Chicago', 'Dallas')"
+			//   The list tokens are retained while parsing the OData query.
+			//   ABNF grammar:
+			//   listExpr  = OPEN BWS commonExpr BWS *( COMMA BWS commonExpr BWS ) CLOSE
+			incrementListArgCount(token)
+			// Push open parens onto the stack
+			stack.Push(token)
+		case token.Value == TokenCloseParen:
+			previousTokenIsLiteral = false
+			if previousToken != nil && previousToken.Value == TokenComma {
+				if cfg&ComplianceIgnoreInvalidComma == 0 {
+					return nil, fmt.Errorf("invalid token sequence: %s %s", previousToken.Value, token.Value)
+				}
+			}
+			// if we find a close paren, pop things off the stack
+			for !stack.Empty() {
+				if stack.Peek().Value == TokenOpenParen {
+					break
+				} else {
+					queue.Enqueue(stack.Pop())
+				}
+			}
+			if stack.Empty() {
+				// there was an error parsing
+				return nil, BadRequestError("Parse error. Mismatched parenthesis.")
+			}
+
+			// Determine if the parenthesis delimiters are:
+			// - A listExpr, possibly an empty list or single element.
+			//   Note a listExpr may be on the left-side or right-side of operators,
+			//   or it may be a list of function arguments.
+			// - A parenExpr, which is used as a precedence delimiter.
+			//
+			// (1, 2, 3) is a listExpr, there is no ambiguity.
+			// (1) matches both listExpr or parenExpr.
+			// parenExpr takes precedence over listExpr.
+			//
+			// For example:
+			//   1 IN (1, 2)  ==> parenthesis is used to create a list of two elements.
+			//   Tags(Key='Environment')/Value ==> variadic list of arguments in property navigation.
+			//   (1) + (2)    ==> parenthesis is a precedence delimiter, i.e. parenExpr.
+
+			// Get the argument count associated with the open paren.
+			// Examples:
+			// (a, b, c) is a listExpr with three arguments.
+			// (arg1='abc',arg2=123) is a listExpr with two arguments.
+			argCount := stack.getArgCount()
+			// pop off open paren
+			stack.Pop()
+
+			isListExpr := false
+			popTokenFromStack := false
+
+			if !stack.Empty() {
+				// Peek the token at the head of the stack.
+				if _, ok := p.Functions[stack.Peek().Value]; ok {
+					// The token is a function followed by a parenthesized expression.
+					// e.g. `func(a1, a2, a3)`
+					// ==> The parenthesized expression is a list expression.
+					popTokenFromStack = true
+					isListExpr = true
+				} else if o1, ok := p.Operators[stack.Peek().Value]; ok {
+					// The token is an operator followed by a parenthesized expression.
+					if o1.PreferListExpr {
+						// The expression is the right operand of an operator that has a preference for listExpr vs parenExpr.
+						isListExpr = true
+					}
+				} else {
+					if stack.Peek().Type == p.LiteralToken {
+						// The token is a odata identifier followed by a parenthesized expression.
+						// E.g. `Product(a1=abc)`:
+						// ==> The parenthesized expression is a list expression.
+						isListExpr = true
+						popTokenFromStack = true
+					}
+				}
+			}
+			if argCount > 1 {
+				isListExpr = true
+			}
+			// When a listExpr contains a single item, it is ambiguous whether it is a listExpr or parenExpr.
+			// For example:
+			// (1) add (2) ==> there is no list involved. There are superfluous parenthesis.
+			// (1, 2) in ( ('a', 'b', 'c'), (1, 2) ):
+			//    This is true because the LHS list (1, 2) is contained in the RHS list.
+			// The following expressions are not the same:
+			//   (1) in ( ('a', 'b', 'c'), (2), 1 )
+			//       ==> false because the LHS does not contain the LHS list (1).
+			//           or should (1) be simplified to the integer 1, which is contained in the RHS?
+			//   1 in ( ('a', 'b', 'c'), (2), 1 )
+			//       ==> true. The number 1 is contained in the RHS list.
+			if isListExpr {
+				// The open parenthesis was a delimiter for a listExpr.
+				// Add a token indicating the number of arguments in the list.
+				queue.Enqueue(&Token{
+					Value: strconv.Itoa(argCount),
+					Type:  TokenTypeArgCount,
+				})
+				// Enqueue a 'list' token if we are processing a ListExpr.
+				queue.Enqueue(&Token{
+					Value: TokenListExpr,
+					Type:  TokenTypeListExpr,
+				})
+			}
+			// if next token is a function or nav collection segment, move it to the queue
+			if popTokenFromStack {
+				queue.Enqueue(stack.Pop())
+			}
+		case token.Value == TokenComma:
+			previousTokenIsLiteral = false
+			if previousToken != nil {
+				switch previousToken.Value {
+				case TokenComma, TokenOpenParen:
+					return nil, fmt.Errorf("invalid token sequence: %s %s", previousToken.Value, token.Value)
+				}
+			}
+			// Function argument separator (",")
+			// Comma may be used as:
+			// 1. Separator of function parameters,
+			// 2. Separator for listExpr such as "City IN ('Seattle', 'San Francisco')"
+			//
+			// Pop off stack until we see a TokenOpenParen
+			for !stack.Empty() && stack.Peek().Value != TokenOpenParen {
+				// This happens when the previous function argument is an expression composed
+				// of multiple tokens, as opposed to a single token. For example:
+				//     max(sin( 5 mul pi ) add 3, sin( 5 ))
+				queue.Enqueue(stack.Pop())
+			}
+			if stack.Empty() {
+				// there was an error parsing. The top of the stack must be open parenthesis
+				return nil, BadRequestError("Parse error")
+			}
+			if stack.Peek().Value != TokenOpenParen {
+				panic("unexpected token")
+			}
+
+		default:
+			if previousTokenIsLiteral {
+				return nil, fmt.Errorf("invalid token sequence: %s %s", previousToken.Value, token.Value)
+			}
+			if token.Type == p.LiteralToken && len(tokens) > 0 && tokens[0].Value == TokenOpenParen {
+				// Literal followed by parenthesis ==> property collection navigation
+				// push property segment onto the stack
+				stack.Push(token)
+			} else {
+				// Token is a literal, number, string... -- put it in the queue
+				queue.Enqueue(token)
+			}
+			incrementListArgCount(token)
+			previousTokenIsLiteral = true
+		}
+		previousToken = token
+	}
+
+	// pop off the remaining operators onto the queue
+	for !stack.Empty() {
+		if stack.Peek().Value == TokenOpenParen || stack.Peek().Value == TokenCloseParen {
+			return nil, BadRequestError("parse error. Mismatched parenthesis.")
+		}
+		queue.Enqueue(stack.Pop())
+	}
+	return &queue, nil
+}
+
+// PostfixToTree converts a Postfix token queue to a parse tree
+func (p *Parser) PostfixToTree(ctx context.Context, queue *tokenQueue) (*ParseNode, error) {
+	stack := &nodeStack{}
+	currNode := &ParseNode{}
+
+	if queue == nil {
+		return nil, errors.New("input queue is nil")
+	}
+	t := queue.Head
+	for t != nil {
+		t = t.Next
+	}
+	// Function to process a list with a variable number of arguments.
+	processVariadicArgs := func(parent *ParseNode) (int, error) {
+
+		// Pop off the count of list arguments.
+		if stack.Empty() {
+			return 0, fmt.Errorf("no argCount token found, stack is empty")
+		}
+		n := stack.Pop()
+		if n.Token.Type != TokenTypeArgCount {
+			return 0, fmt.Errorf("expected arg count token, got '%v'", n.Token.Type)
+		}
+		argCount, err := strconv.Atoi(n.Token.Value)
+		if err != nil {
+			return 0, err
+		}
+		for i := 0; i < argCount; i++ {
+			if stack.Empty() {
+				return 0, fmt.Errorf("missing argument found. '%s'", parent.Token.Value)
+			}
+			c := stack.Pop()
+			// Attach the operand to its parent node which represents the function/operator
+			c.Parent = parent
+			// prepend children so they get added in the right order
+			parent.Children = append([]*ParseNode{c}, parent.Children...)
+		}
+		return argCount, nil
+	}
+	for !queue.Empty() {
+		// push the token onto the stack as a tree node
+		currToken := queue.Dequeue()
+		currNode = &ParseNode{currToken, nil, make([]*ParseNode, 0)}
+		stack.Push(currNode)
+
+		stackHeadToken := stack.Peek().Token
+		switch {
+		case p.isFunction(stackHeadToken):
+			// The top of the stack is a function, pop off the function.
+			node := stack.Pop()
+
+			// Pop off the list expression.
+			if stack.Empty() {
+				return nil, fmt.Errorf("no list expression token found, stack is empty")
+			}
+			n := stack.Pop()
+			if n.Token.Type != TokenTypeListExpr {
+				return nil, fmt.Errorf("expected list expression token, got '%v'", n.Token.Type)
+			}
+
+			if node.Token.Type == ExpressionTokenCase {
+				// Create argument pairs for case() statement by translating flat list into pairs
+				if len(n.Children)%2 != 0 {
+					return nil, fmt.Errorf("expected even number of comma-separated arguments to case statement")
+				}
+				for i:=0; i<len(n.Children); i+=2 {
+					if !p.isBooleanExpression(n.Children[i].Token) {
+						return nil, fmt.Errorf("expected boolean expression in case statement")
+					}
+					c := &ParseNode{
+						Token:    &Token{Type: ExpressionTokenCasePair},
+						Parent:   node,
+						Children: []*ParseNode{n.Children[i],n.Children[i+1]},
+					}
+					node.Children = append(node.Children, c)
+				}
+			} else {
+				// Collapse function arguments as direct children of function node
+				for _, c := range n.Children {
+					c.Parent = node
+				}
+				node.Children = n.Children
+			}
+
+			// Some functions, e.g. substring, can take a variable number of arguments. Enforce legal number of arguments
+			foundMatch := false
+			f := p.Functions[node.Token.Value]
+			for _, expectedArgCount := range f.Params {
+				if len(node.Children) == expectedArgCount {
+					foundMatch = true
+					break
+				}
+			}
+			if !foundMatch {
+				return nil, fmt.Errorf("invalid number of arguments for function '%s'. Got %d argument. Expected: %v",
+					node.Token.Value, len(node.Children), f.Params)
+			}
+			stack.Push(node)
+		case p.isOperator(stackHeadToken):
+			// if the top of the stack is an operator
+			node := stack.Pop()
+			o := p.Operators[node.Token.Value]
+			// pop off operands
+			for i := 0; i < o.Operands; i++ {
+				if stack.Empty() {
+					return nil, fmt.Errorf("insufficient number of operands for operator '%s'", node.Token.Value)
+				}
+				// prepend children so they get added in the right order
+				c := stack.Pop()
+				c.Parent = node
+				node.Children = append([]*ParseNode{c}, node.Children...)
+			}
+			stack.Push(node)
+		case TokenTypeListExpr == stackHeadToken.Type:
+			// ListExpr: List of items
+			// Pop off the list expression.
+			node := stack.Pop()
+			if _, err := processVariadicArgs(node); err != nil {
+				return nil, err
+			}
+			stack.Push(node)
+		case p.LiteralToken == stackHeadToken.Type:
+			// Pop off the property literal.
+			node := stack.Pop()
+
+			if !stack.Empty() && stack.Peek().Token.Type == TokenTypeListExpr {
+				// Pop off the list expression.
+				n := stack.Pop()
+				for _, c := range n.Children {
+					c.Parent = node
+				}
+				node.Children = n.Children
+			}
+			stack.Push(node)
+		}
+	}
+	// If all tokens have been processed, the stack should have zero or one element.
+	if stack.Head != nil && stack.Head.Prev != nil {
+		return nil, errors.New("invalid expression")
+	}
+	return currNode, nil
+}
+
+type tokenStack struct {
+	Head *tokenStackNode
+	Size int
+}
+
+type tokenStackNode struct {
+	Token        *Token          // The token value.
+	Prev         *tokenStackNode // The previous node in the stack.
+	listArgCount int             // The number of arguments in a listExpr.
+}
+
+func (s *tokenStack) Push(t *Token) {
+	node := tokenStackNode{Token: t, Prev: s.Head}
+	s.Head = &node
+	s.Size++
+}
+
+func (s *tokenStack) Pop() *Token {
+	node := s.Head
+	s.Head = node.Prev
+	s.Size--
+	return node.Token
+}
+
+// Peek returns the token at head of the stack.
+// The stack is not modified.
+// A panic occurs if the stack is empty.
+func (s *tokenStack) Peek() *Token {
+	return s.Head.Token
+}
+
+func (s *tokenStack) Empty() bool {
+	return s.Head == nil
+}
+
+func (s *tokenStack) getArgCount() int {
+	return s.Head.listArgCount
+}
+
+func (s *tokenStack) String() string {
+	output := ""
+	currNode := s.Head
+	for currNode != nil {
+		output = currNode.Token.Value + " " + output
+		currNode = currNode.Prev
+	}
+	return output
+}
+
+type tokenQueue struct {
+	Head *tokenQueueNode
+	Tail *tokenQueueNode
+}
+
+type tokenQueueNode struct {
+	Token *Token
+	Prev  *tokenQueueNode
+	Next  *tokenQueueNode
+}
+
+// Enqueue adds the specified token at the tail of the queue.
+func (q *tokenQueue) Enqueue(t *Token) {
+	node := tokenQueueNode{t, q.Tail, nil}
+	//fmt.Println(t.Value)
+
+	if q.Tail == nil {
+		q.Head = &node
+	} else {
+		q.Tail.Next = &node
+	}
+
+	q.Tail = &node
+}
+
+// Dequeue removes the token at the head of the queue and returns the token.
+func (q *tokenQueue) Dequeue() *Token {
+	node := q.Head
+	if node.Next != nil {
+		node.Next.Prev = nil
+	}
+	q.Head = node.Next
+	if q.Head == nil {
+		q.Tail = nil
+	}
+	return node.Token
+}
+
+func (q *tokenQueue) Empty() bool {
+	return q.Head == nil && q.Tail == nil
+}
+
+func (q *tokenQueue) String() string {
+	var sb strings.Builder
+	node := q.Head
+	for node != nil {
+		sb.WriteString(fmt.Sprintf("%s[%v]", node.Token.Value, node.Token.Type))
+		node = node.Next
+		if node != nil {
+			sb.WriteRune(' ')
+		}
+	}
+	return sb.String()
+}
+
+func (q *tokenQueue) GetValue() string {
+	var sb strings.Builder
+	node := q.Head
+	for node != nil {
+		sb.WriteString(node.Token.Value)
+		node = node.Next
+	}
+	return sb.String()
+}
+
+type nodeStack struct {
+	Head *nodeStackNode
+}
+
+type nodeStackNode struct {
+	ParseNode *ParseNode
+	Prev      *nodeStackNode
+}
+
+func (s *nodeStack) Push(n *ParseNode) {
+	node := nodeStackNode{ParseNode: n, Prev: s.Head}
+	s.Head = &node
+}
+
+func (s *nodeStack) Pop() *ParseNode {
+	node := s.Head
+	s.Head = node.Prev
+	return node.ParseNode
+}
+
+func (s *nodeStack) Peek() *ParseNode {
+	return s.Head.ParseNode
+}
+
+func (s *nodeStack) Empty() bool {
+	return s.Head == nil
+}
+
+func (s *nodeStack) String() string {
+	var sb strings.Builder
+	currNode := s.Head
+	for currNode != nil {
+		sb.WriteRune(' ')
+		sb.WriteString(currNode.ParseNode.Token.Value)
+		currNode = currNode.Prev
+	}
+	return sb.String()
+}
@@ -0,0 +1,241 @@
+package godata
+
+type GoDataIdentifier map[string]string
+
+type RequestKind int
+
+const (
+	RequestKindUnknown RequestKind = iota
+	RequestKindMetadata
+	RequestKindService
+	RequestKindEntity
+	RequestKindCollection
+	RequestKindSingleton
+	RequestKindProperty
+	RequestKindPropertyValue
+	RequestKindRef
+	RequestKindCount
+)
+
+type SemanticType int
+
+const (
+	SemanticTypeUnknown SemanticType = iota
+	SemanticTypeEntity
+	SemanticTypeEntitySet
+	SemanticTypeDerivedEntity
+	SemanticTypeAction
+	SemanticTypeFunction
+	SemanticTypeProperty
+	SemanticTypePropertyValue
+	SemanticTypeRef
+	SemanticTypeCount
+	SemanticTypeMetadata
+)
+
+type GoDataRequest struct {
+	FirstSegment *GoDataSegment
+	LastSegment  *GoDataSegment
+	Query        *GoDataQuery
+	RequestKind  RequestKind
+}
+
+// Represents a segment (slash-separated) part of the URI path. Each segment
+// has a link to the next segment (the last segment precedes nil).
+type GoDataSegment struct {
+	// The raw segment parsed from the URI
+	RawValue string
+
+	// The kind of resource being pointed at by this segment
+	SemanticType SemanticType
+
+	// A pointer to the metadata type this object represents, as defined by a
+	// particular service
+	SemanticReference interface{}
+
+	// The name of the entity, type, collection, etc.
+	Name string
+
+	// map[string]string of identifiers passed to this segment. If the identifier
+	// is not key/value pair(s), then all values will be nil. If there is no
+	// identifier, it will be nil.
+	Identifier *GoDataIdentifier
+
+	// The next segment in the path.
+	Next *GoDataSegment
+	// The previous segment in the path.
+	Prev *GoDataSegment
+}
+
+type GoDataQuery struct {
+	Filter      *GoDataFilterQuery
+	At          *GoDataFilterQuery
+	Apply       *GoDataApplyQuery
+	Expand      *GoDataExpandQuery
+	Select      *GoDataSelectQuery
+	OrderBy     *GoDataOrderByQuery
+	Top         *GoDataTopQuery
+	Skip        *GoDataSkipQuery
+	Count       *GoDataCountQuery
+	InlineCount *GoDataInlineCountQuery
+	Search      *GoDataSearchQuery
+	Compute     *GoDataComputeQuery
+	Format      *GoDataFormatQuery
+}
+
+// GoDataExpression encapsulates the tree representation of an expression
+// as defined in the OData ABNF grammar.
+type GoDataExpression struct {
+	Tree *ParseNode
+	// The raw string representing an expression
+	RawValue string
+}
+
+// Stores a parsed version of the filter query string. Can be used by
+// providers to apply the filter based on their own implementation. The filter
+// is stored as a parse tree that can be traversed.
+type GoDataFilterQuery struct {
+	Tree *ParseNode
+	// The raw filter string
+	RawValue string
+}
+
+type GoDataApplyQuery string
+
+type GoDataExpandQuery struct {
+	ExpandItems []*ExpandItem
+}
+
+type GoDataSelectQuery struct {
+	SelectItems []*SelectItem
+	// The raw select string
+	RawValue string
+}
+
+type GoDataOrderByQuery struct {
+	OrderByItems []*OrderByItem
+	// The raw orderby string
+	RawValue string
+}
+
+type GoDataTopQuery int
+
+type GoDataSkipQuery int
+
+type GoDataCountQuery bool
+
+type GoDataInlineCountQuery string
+
+type GoDataSearchQuery struct {
+	Tree *ParseNode
+	// The raw search string
+	RawValue string
+}
+
+type GoDataComputeQuery struct {
+	ComputeItems []*ComputeItem
+	// The raw compute string
+	RawValue string
+}
+
+type GoDataFormatQuery struct {
+}
+
+// Check if this identifier has more than one key/value pair.
+func (id *GoDataIdentifier) HasMultiple() bool {
+	count := 0
+	for range map[string]string(*id) {
+		count++
+	}
+	return count > 1
+}
+
+// Return the first key in the map. This is how you should get the identifier
+// for single values, e.g. when the path is Employee(1), etc.
+func (id *GoDataIdentifier) Get() string {
+	for k := range map[string]string(*id) {
+		return k
+	}
+	return ""
+}
+
+// Return a specific value for a specific key.
+func (id *GoDataIdentifier) GetKey(key string) (string, bool) {
+	v, ok := map[string]string(*id)[key]
+	return v, ok
+}
+
+// GoDataCommonStructure represents either a GoDataQuery or ExpandItem in a uniform manner
+// as a Go interface. This allows the writing of functional logic that can work on either type,
+// such as a provider implementation which starts at the GoDataQuery and walks any nested ExpandItem
+// in an identical manner.
+type GoDataCommonStructure interface {
+	GetFilter() *GoDataFilterQuery
+	GetAt() *GoDataFilterQuery
+	GetApply() *GoDataApplyQuery
+	GetExpand() *GoDataExpandQuery
+	GetSelect() *GoDataSelectQuery
+	GetOrderBy() *GoDataOrderByQuery
+	GetTop() *GoDataTopQuery
+	GetSkip() *GoDataSkipQuery
+	GetCount() *GoDataCountQuery
+	GetInlineCount() *GoDataInlineCountQuery
+	GetSearch() *GoDataSearchQuery
+	GetCompute() *GoDataComputeQuery
+	GetFormat() *GoDataFormatQuery
+	// AddExpandItem adds an item to the list of expand clauses in the underlying GoDataQuery/ExpandItem
+	// structure.
+	// AddExpandItem may be used to add items based on the requirements of the application using godata.
+	// For example applications may support the introduction of dynamic navigational fields using $compute.
+	// A possible implementation is to parse the request url using godata and then during semantic
+	// post-processing identify dynamic navigation properties and call AddExpandItem to add them to the
+	// list of expanded fields.
+	AddExpandItem(*ExpandItem)
+}
+
+// GoDataQuery implementation of GoDataCommonStructure interface
+func (o *GoDataQuery) GetFilter() *GoDataFilterQuery           { return o.Filter }
+func (o *GoDataQuery) GetAt() *GoDataFilterQuery               { return o.At }
+func (o *GoDataQuery) GetApply() *GoDataApplyQuery             { return o.Apply }
+func (o *GoDataQuery) GetExpand() *GoDataExpandQuery           { return o.Expand }
+func (o *GoDataQuery) GetSelect() *GoDataSelectQuery           { return o.Select }
+func (o *GoDataQuery) GetOrderBy() *GoDataOrderByQuery         { return o.OrderBy }
+func (o *GoDataQuery) GetTop() *GoDataTopQuery                 { return o.Top }
+func (o *GoDataQuery) GetSkip() *GoDataSkipQuery               { return o.Skip }
+func (o *GoDataQuery) GetCount() *GoDataCountQuery             { return o.Count }
+func (o *GoDataQuery) GetInlineCount() *GoDataInlineCountQuery { return o.InlineCount }
+func (o *GoDataQuery) GetSearch() *GoDataSearchQuery           { return o.Search }
+func (o *GoDataQuery) GetCompute() *GoDataComputeQuery         { return o.Compute }
+func (o *GoDataQuery) GetFormat() *GoDataFormatQuery           { return o.Format }
+
+// AddExpandItem adds an expand clause to the toplevel odata request structure 'o'.
+func (o *GoDataQuery) AddExpandItem(item *ExpandItem) {
+	if o.Expand == nil {
+		o.Expand = &GoDataExpandQuery{}
+	}
+	o.Expand.ExpandItems = append(o.Expand.ExpandItems, item)
+}
+
+// ExpandItem implementation of GoDataCommonStructure interface
+func (o *ExpandItem) GetFilter() *GoDataFilterQuery           { return o.Filter }
+func (o *ExpandItem) GetAt() *GoDataFilterQuery               { return o.At }
+func (o *ExpandItem) GetApply() *GoDataApplyQuery             { return nil }
+func (o *ExpandItem) GetExpand() *GoDataExpandQuery           { return o.Expand }
+func (o *ExpandItem) GetSelect() *GoDataSelectQuery           { return o.Select }
+func (o *ExpandItem) GetOrderBy() *GoDataOrderByQuery         { return o.OrderBy }
+func (o *ExpandItem) GetTop() *GoDataTopQuery                 { return o.Top }
+func (o *ExpandItem) GetSkip() *GoDataSkipQuery               { return o.Skip }
+func (o *ExpandItem) GetCount() *GoDataCountQuery             { return nil }
+func (o *ExpandItem) GetInlineCount() *GoDataInlineCountQuery { return nil }
+func (o *ExpandItem) GetSearch() *GoDataSearchQuery           { return o.Search }
+func (o *ExpandItem) GetCompute() *GoDataComputeQuery         { return o.Compute }
+func (o *ExpandItem) GetFormat() *GoDataFormatQuery           { return nil }
+
+// AddExpandItem adds an expand clause to 'o' creating a nested expand, ie $expand 'item'
+// nested within $expand 'o'.
+func (o *ExpandItem) AddExpandItem(item *ExpandItem) {
+	if o.Expand == nil {
+		o.Expand = &GoDataExpandQuery{}
+	}
+	o.Expand.ExpandItems = append(o.Expand.ExpandItems, item)
+}
@@ -0,0 +1,104 @@
+package godata
+
+import (
+	"bytes"
+	"strconv"
+)
+
+// A response is a dictionary of keys to their corresponding fields. This will
+// be converted into a JSON dictionary in the response to the web client.
+type GoDataResponse struct {
+	Fields map[string]*GoDataResponseField
+}
+
+// Serialize the result as JSON for sending to the client. If an error
+// occurs during the serialization, it will be returned.
+func (r *GoDataResponse) Json() ([]byte, error) {
+	result, err := prepareJsonDict(r.Fields)
+	if err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+// A response that is a primitive JSON type or a list or a dictionary. When
+// writing to JSON, it is automatically mapped from the Go type to a suitable
+// JSON data type. Any type can be used, but if the data type is not supported
+// for serialization, then an error is thrown.
+type GoDataResponseField struct {
+	Value interface{}
+}
+
+// Convert the response field to a JSON serialized form. If the type is not
+// string, []byte, int, float64, map[string]*GoDataResponseField, or
+// []*GoDataResponseField, then an error will be thrown.
+func (f *GoDataResponseField) Json() ([]byte, error) {
+	switch f.Value.(type) {
+	case string:
+		return prepareJsonString([]byte(f.Value.(string)))
+	case []byte:
+		return prepareJsonString(f.Value.([]byte))
+	case int:
+		return []byte(strconv.Itoa(f.Value.(int))), nil
+	case float64:
+		return []byte(strconv.FormatFloat(f.Value.(float64), 'f', -1, 64)), nil
+	case map[string]*GoDataResponseField:
+		return prepareJsonDict(f.Value.(map[string]*GoDataResponseField))
+	case []*GoDataResponseField:
+		return prepareJsonList(f.Value.([]*GoDataResponseField))
+	default:
+		return nil, InternalServerError("Response field type not recognized.")
+	}
+}
+
+func prepareJsonString(s []byte) ([]byte, error) {
+	// escape double quotes
+	s = bytes.Replace(s, []byte("\""), []byte("\\\""), -1)
+	var buf bytes.Buffer
+	buf.WriteByte('"')
+	buf.Write(s)
+	buf.WriteByte('"')
+	return buf.Bytes(), nil
+}
+
+func prepareJsonDict(d map[string]*GoDataResponseField) ([]byte, error) {
+	var buf bytes.Buffer
+	buf.WriteByte('{')
+	count := 0
+	for k, v := range d {
+		buf.WriteByte('"')
+		buf.Write([]byte(k))
+		buf.WriteByte('"')
+		buf.WriteByte(':')
+		field, err := v.Json()
+		if err != nil {
+			return nil, err
+		}
+		buf.Write(field)
+		count++
+		if count < len(d) {
+			buf.WriteByte(',')
+		}
+	}
+	buf.WriteByte('}')
+	return buf.Bytes(), nil
+}
+
+func prepareJsonList(l []*GoDataResponseField) ([]byte, error) {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	count := 0
+	for _, v := range l {
+		field, err := v.Json()
+		if err != nil {
+			return nil, err
+		}
+		buf.Write(field)
+		count++
+		if count < len(l) {
+			buf.WriteByte(',')
+		}
+	}
+	buf.WriteByte(']')
+	return buf.Bytes(), nil
+}
@@ -0,0 +1,59 @@
+package godata
+
+import "context"
+
+type SearchTokenType int
+
+func (s SearchTokenType) Value() int {
+	return (int)(s)
+}
+
+const (
+	SearchTokenLiteral SearchTokenType = iota
+	SearchTokenOpenParen
+	SearchTokenCloseParen
+	SearchTokenOp
+	SearchTokenWhitespace
+)
+
+var GlobalSearchTokenizer = SearchTokenizer()
+var GlobalSearchParser = SearchParser()
+
+// Convert an input string from the $filter part of the URL into a parse
+// tree that can be used by providers to create a response.
+func ParseSearchString(ctx context.Context, filter string) (*GoDataSearchQuery, error) {
+	tokens, err := GlobalSearchTokenizer.Tokenize(ctx, filter)
+	if err != nil {
+		return nil, err
+	}
+	postfix, err := GlobalSearchParser.InfixToPostfix(ctx, tokens)
+	if err != nil {
+		return nil, err
+	}
+	tree, err := GlobalSearchParser.PostfixToTree(ctx, postfix)
+	if err != nil {
+		return nil, err
+	}
+	return &GoDataSearchQuery{tree, filter}, nil
+}
+
+// Create a tokenizer capable of tokenizing filter statements
+func SearchTokenizer() *Tokenizer {
+	t := Tokenizer{}
+	t.Add("^\\\"[^\\\"]+\\\"", SearchTokenLiteral)
+	t.Add("^\\(", SearchTokenOpenParen)
+	t.Add("^\\)", SearchTokenCloseParen)
+	t.Add("^(OR|AND|NOT)", SearchTokenOp)
+	t.Add("^[\\w]+", SearchTokenLiteral)
+	t.Ignore("^ ", SearchTokenWhitespace)
+
+	return &t
+}
+
+func SearchParser() *Parser {
+	parser := EmptyParser()
+	parser.DefineOperator("NOT", 1, OpAssociationNone, 3)
+	parser.DefineOperator("AND", 2, OpAssociationLeft, 2)
+	parser.DefineOperator("OR", 2, OpAssociationLeft, 1)
+	return parser
+}
@@ -0,0 +1,97 @@
+package godata
+
+import (
+	"context"
+	"errors"
+	"strings"
+)
+
+type SelectItem struct {
+	Segments []*Token
+}
+
+func ParseSelectString(ctx context.Context, sel string) (*GoDataSelectQuery, error) {
+	return GlobalExpressionParser.ParseSelectString(ctx, sel)
+}
+
+func (p *ExpressionParser) ParseSelectString(ctx context.Context, sel string) (*GoDataSelectQuery, error) {
+	items := strings.Split(sel, ",")
+
+	result := []*SelectItem{}
+
+	for _, item := range items {
+		item = strings.TrimSpace(item)
+
+		cfg, hasComplianceConfig := ctx.Value(odataCompliance).(OdataComplianceConfig)
+		if !hasComplianceConfig {
+			// Strict ODATA compliance by default.
+			cfg = ComplianceStrict
+		}
+
+		if len(strings.TrimSpace(item)) == 0 && cfg&ComplianceIgnoreInvalidComma == 0 {
+			return nil, BadRequestError("Extra comma in $select.")
+		}
+
+		if _, err := p.tokenizer.Tokenize(ctx, item); err != nil {
+			switch e := err.(type) {
+			case *GoDataError:
+				return nil, &GoDataError{
+					ResponseCode: e.ResponseCode,
+					Message:      "Invalid $select value",
+					Cause:        e,
+				}
+			default:
+				return nil, &GoDataError{
+					ResponseCode: 500,
+					Message:      "Invalid $select value",
+					Cause:        e,
+				}
+			}
+		} else {
+			segments := []*Token{}
+			for _, val := range strings.Split(item, "/") {
+				segments = append(segments, &Token{Value: val})
+			}
+			result = append(result, &SelectItem{segments})
+		}
+	}
+
+	return &GoDataSelectQuery{result, sel}, nil
+}
+
+func SemanticizeSelectQuery(sel *GoDataSelectQuery, service *GoDataService, entity *GoDataEntityType) error {
+	if sel == nil {
+		return nil
+	}
+
+	newItems := []*SelectItem{}
+
+	// replace wildcards with every property of the entity
+	for _, item := range sel.SelectItems {
+		// TODO: allow multiple path segments
+		if len(item.Segments) > 1 {
+			return NotImplementedError("Multiple path segments in select clauses are not yet supported.")
+		}
+
+		if item.Segments[0].Value == "*" {
+			for _, prop := range service.PropertyLookup[entity] {
+				newItems = append(newItems, &SelectItem{[]*Token{{Value: prop.Name}}})
+			}
+		} else {
+			newItems = append(newItems, item)
+		}
+	}
+
+	sel.SelectItems = newItems
+
+	for _, item := range sel.SelectItems {
+		if prop, ok := service.PropertyLookup[entity][item.Segments[0].Value]; ok {
+			item.Segments[0].SemanticType = SemanticTypeProperty
+			item.Segments[0].SemanticReference = prop
+		} else {
+			return errors.New("Entity " + entity.Name + " has no property " + item.Segments[0].Value)
+		}
+	}
+
+	return nil
+}
@@ -0,0 +1,442 @@
+package godata
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+const (
+	ODataFieldContext string = "@odata.context"
+	ODataFieldCount   string = "@odata.count"
+	ODataFieldValue   string = "value"
+)
+
+// The basic interface for a GoData provider. All providers must implement
+// these functions.
+type GoDataProvider interface {
+	// Request a single entity from the provider. Should return a response field
+	// that contains the value mapping properties to values for the entity.
+	GetEntity(*GoDataRequest) (*GoDataResponseField, error)
+	// Request a collection of entities from the provider. Should return a
+	// response field that contains the value of a slice of every entity in the
+	// collection filtered by the request query parameters.
+	GetEntityCollection(*GoDataRequest) (*GoDataResponseField, error)
+	// Request the number of entities in a collection, disregarding any filter
+	// query parameters.
+	GetCount(*GoDataRequest) (int, error)
+	// Get the object model representation from the provider.
+	GetMetadata() *GoDataMetadata
+}
+
+// A GoDataService will spawn an HTTP listener, which will connect GoData
+// requests with a backend provider given to it.
+type GoDataService struct {
+	// The base url for the service. Navigating to this URL will display the
+	// service document.
+	BaseUrl *url.URL
+	// The provider for this service that is serving the data to the OData API.
+	Provider GoDataProvider
+	// Metadata cache taken from the provider.
+	Metadata *GoDataMetadata
+	// A mapping from schema names to schema references
+	SchemaLookup map[string]*GoDataSchema
+	// A bottom-up mapping from entity type names to schema namespaces to
+	// the entity type reference
+	EntityTypeLookup map[string]map[string]*GoDataEntityType
+	// A bottom-up mapping from entity container names to schema namespaces to
+	// the entity container reference
+	EntityContainerLookup map[string]map[string]*GoDataEntityContainer
+	// A bottom-up mapping from entity set names to entity collection names to
+	// schema namespaces to the entity set reference
+	EntitySetLookup map[string]map[string]map[string]*GoDataEntitySet
+	// A lookup for entity properties if an entity type is given, lookup
+	// properties by name
+	PropertyLookup map[*GoDataEntityType]map[string]*GoDataProperty
+	// A lookup for navigational properties if an entity type is given,
+	// lookup navigational properties by name
+	NavigationPropertyLookup map[*GoDataEntityType]map[string]*GoDataNavigationProperty
+}
+
+type providerChannelResponse struct {
+	Field *GoDataResponseField
+	Error error
+}
+
+// Create a new service from a given provider. This step builds lookups for
+// all parts of the data model, so constant time lookups can be performed. This
+// step only happens once when the server starts up, so the overall cost is
+// minimal. The given url will be treated as the base URL for all service
+// requests, and used for building context URLs, etc.
+func BuildService(provider GoDataProvider, serviceUrl string) (*GoDataService, error) {
+	metadata := provider.GetMetadata()
+
+	// build the lookups from the metadata
+	schemaLookup := map[string]*GoDataSchema{}
+	entityLookup := map[string]map[string]*GoDataEntityType{}
+	containerLookup := map[string]map[string]*GoDataEntityContainer{}
+	entitySetLookup := map[string]map[string]map[string]*GoDataEntitySet{}
+	propertyLookup := map[*GoDataEntityType]map[string]*GoDataProperty{}
+	navPropLookup := map[*GoDataEntityType]map[string]*GoDataNavigationProperty{}
+
+	for _, schema := range metadata.DataServices.Schemas {
+		schemaLookup[schema.Namespace] = schema
+
+		for _, entity := range schema.EntityTypes {
+			if _, ok := entityLookup[entity.Name]; !ok {
+				entityLookup[entity.Name] = map[string]*GoDataEntityType{}
+			}
+			if _, ok := propertyLookup[entity]; !ok {
+				propertyLookup[entity] = map[string]*GoDataProperty{}
+			}
+			if _, ok := navPropLookup[entity]; !ok {
+				navPropLookup[entity] = map[string]*GoDataNavigationProperty{}
+			}
+			entityLookup[entity.Name][schema.Namespace] = entity
+
+			for _, prop := range entity.Properties {
+				propertyLookup[entity][prop.Name] = prop
+			}
+			for _, prop := range entity.NavigationProperties {
+				navPropLookup[entity][prop.Name] = prop
+			}
+		}
+
+		for _, container := range schema.EntityContainers {
+			if _, ok := containerLookup[container.Name]; !ok {
+				containerLookup[container.Name] = map[string]*GoDataEntityContainer{}
+			}
+			containerLookup[container.Name][schema.Namespace] = container
+
+			for _, set := range container.EntitySets {
+				if _, ok := entitySetLookup[set.Name]; !ok {
+					entitySetLookup[set.Name] = map[string]map[string]*GoDataEntitySet{}
+				}
+				if _, ok := entitySetLookup[set.Name][container.Name]; !ok {
+					entitySetLookup[set.Name][container.Name] = map[string]*GoDataEntitySet{}
+				}
+				entitySetLookup[set.Name][container.Name][schema.Namespace] = set
+			}
+		}
+	}
+
+	parsedUrl, err := url.Parse(serviceUrl)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &GoDataService{
+		parsedUrl,
+		provider,
+		provider.GetMetadata(),
+		schemaLookup,
+		entityLookup,
+		containerLookup,
+		entitySetLookup,
+		propertyLookup,
+		navPropLookup,
+	}, nil
+}
+
+// The default handler for parsing requests as GoDataRequests, passing them
+// to a GoData provider, and then building a response.
+func (service *GoDataService) GoDataHTTPHandler(w http.ResponseWriter, r *http.Request) {
+	ctx := context.Background()
+	request, err := ParseRequest(ctx, r.URL.Path, r.URL.Query())
+
+	if err != nil {
+		panic(err) // TODO: return proper error
+	}
+
+	// Semanticize all tokens in the request, connecting them with their
+	// corresponding types in the service
+	err = request.SemanticizeRequest(service)
+
+	if err != nil {
+		panic(err) // TODO: return proper error
+	}
+
+	// TODO: differentiate GET and POST requests
+	var response []byte = []byte{}
+	if request.RequestKind == RequestKindMetadata {
+		response, err = service.buildMetadataResponse(request)
+	} else if request.RequestKind == RequestKindService {
+		response, err = service.buildServiceResponse(request)
+	} else if request.RequestKind == RequestKindCollection {
+		response, err = service.buildCollectionResponse(request)
+	} else if request.RequestKind == RequestKindEntity {
+		response, err = service.buildEntityResponse(request)
+	} else if request.RequestKind == RequestKindProperty {
+		response, err = service.buildPropertyResponse(request)
+	} else if request.RequestKind == RequestKindPropertyValue {
+		response, err = service.buildPropertyValueResponse(request)
+	} else if request.RequestKind == RequestKindCount {
+		response, err = service.buildCountResponse(request)
+	} else if request.RequestKind == RequestKindRef {
+		response, err = service.buildRefResponse(request)
+	} else {
+		err = NotImplementedError("Request type not understood.")
+	}
+
+	if err != nil {
+		panic(err) // TODO: return proper error
+	}
+
+	_, err = w.Write(response)
+	if err != nil {
+		panic(err) // TODO: return proper error
+	}
+}
+
+func (service *GoDataService) buildMetadataResponse(request *GoDataRequest) ([]byte, error) {
+	return service.Metadata.Bytes()
+}
+
+func (service *GoDataService) buildServiceResponse(request *GoDataRequest) ([]byte, error) {
+	// TODO
+	return nil, NotImplementedError("Service responses are not implemented yet.")
+}
+
+func (service *GoDataService) buildCollectionResponse(request *GoDataRequest) ([]byte, error) {
+	response := &GoDataResponse{Fields: map[string]*GoDataResponseField{}}
+	// get request from provider
+	responses := make(chan *providerChannelResponse)
+	go func() {
+		result, err := service.Provider.GetEntityCollection(request)
+		responses <- &providerChannelResponse{result, err}
+		close(responses)
+	}()
+
+	if bool(*request.Query.Count) {
+		// if count is true, also include the count result
+		counts := make(chan *providerChannelResponse)
+
+		go func() {
+			result, err := service.Provider.GetCount(request)
+			counts <- &providerChannelResponse{&GoDataResponseField{result}, err}
+			close(counts)
+		}()
+
+		r := <-counts
+		if r.Error != nil {
+			return nil, r.Error
+		}
+
+		response.Fields[ODataFieldCount] = r.Field
+	}
+	// build context URL
+	context := request.LastSegment.SemanticReference.(*GoDataEntitySet).Name
+	path, err := url.Parse("./$metadata#" + context)
+	if err != nil {
+		return nil, err
+	}
+	contextUrl := service.BaseUrl.ResolveReference(path).String()
+	response.Fields[ODataFieldContext] = &GoDataResponseField{Value: contextUrl}
+
+	// wait for a response from the provider
+	r := <-responses
+
+	if r.Error != nil {
+		return nil, r.Error
+	}
+
+	response.Fields[ODataFieldValue] = r.Field
+
+	return response.Json()
+}
+
+func (service *GoDataService) buildEntityResponse(request *GoDataRequest) ([]byte, error) {
+	// get request from provider
+	responses := make(chan *providerChannelResponse)
+	go func() {
+		result, err := service.Provider.GetEntity(request)
+		responses <- &providerChannelResponse{result, err}
+		close(responses)
+	}()
+
+	// build context URL
+	context := request.LastSegment.SemanticReference.(*GoDataEntitySet).Name
+	path, err := url.Parse("./$metadata#" + context + "/$entity")
+	if err != nil {
+		return nil, err
+	}
+	contextUrl := service.BaseUrl.ResolveReference(path).String()
+
+	// wait for a response from the provider
+	r := <-responses
+
+	if r.Error != nil {
+		return nil, r.Error
+	}
+
+	// Add context field to result and create the response
+	switch r.Field.Value.(type) {
+	case map[string]*GoDataResponseField:
+		fields := r.Field.Value.(map[string]*GoDataResponseField)
+		fields[ODataFieldContext] = &GoDataResponseField{Value: contextUrl}
+		response := &GoDataResponse{Fields: fields}
+
+		return response.Json()
+	default:
+		return nil, InternalServerError("Provider did not return a valid response" +
+			" from GetEntity()")
+	}
+}
+
+func (service *GoDataService) buildPropertyResponse(request *GoDataRequest) ([]byte, error) {
+	// TODO
+	return nil, NotImplementedError("Property responses are not implemented yet.")
+}
+
+func (service *GoDataService) buildPropertyValueResponse(request *GoDataRequest) ([]byte, error) {
+	// TODO
+	return nil, NotImplementedError("Property value responses are not implemented yet.")
+}
+
+func (service *GoDataService) buildCountResponse(request *GoDataRequest) ([]byte, error) {
+	// get request from provider
+	responses := make(chan *providerChannelResponse)
+	go func() {
+		result, err := service.Provider.GetCount(request)
+		responses <- &providerChannelResponse{&GoDataResponseField{result}, err}
+		close(responses)
+	}()
+
+	// wait for a response from the provider
+	r := <-responses
+
+	if r.Error != nil {
+		return nil, r.Error
+	}
+
+	return r.Field.Json()
+}
+
+func (service *GoDataService) buildRefResponse(request *GoDataRequest) ([]byte, error) {
+	// TODO
+	return nil, NotImplementedError("Ref responses are not implemented yet.")
+}
+
+// Start the service listening on the given address.
+func (service *GoDataService) ListenAndServe(addr string) {
+	http.HandleFunc("/", service.GoDataHTTPHandler)
+	if err := http.ListenAndServe(addr, nil); err != nil {
+		panic(err) // TODO: return proper error
+	}
+}
+
+// Lookup an entity type from the service metadata. Accepts a fully qualified
+// name, e.g., ODataService.EntityTypeName or, if unambiguous, accepts a
+// simple identifier, e.g., EntityTypeName.
+func (service *GoDataService) LookupEntityType(name string) (*GoDataEntityType, error) {
+	// strip "Collection()" and just return the raw entity type
+	// The provider should keep track of what are collections and what aren't
+	if strings.Contains(name, "(") && strings.Contains(name, ")") {
+		name = name[strings.Index(name, "(")+1 : strings.LastIndex(name, ")")]
+	}
+
+	parts := strings.Split(name, ".")
+	entityName := parts[len(parts)-1]
+	// remove entity from the list of parts
+	parts = parts[:len(parts)-1]
+
+	schemas, ok := service.EntityTypeLookup[entityName]
+	if !ok {
+		return nil, BadRequestError("Entity " + name + " does not exist.")
+	}
+
+	if len(parts) > 0 {
+		// namespace is provided
+		entity, ok := schemas[parts[len(parts)-1]]
+		if !ok {
+			return nil, BadRequestError("Entity " + name + " not found in given namespace.")
+		}
+		return entity, nil
+	} else {
+		// no namespace, just return the first one
+
+		// throw error if ambiguous
+		if len(schemas) > 1 {
+			return nil, BadRequestError("Entity " + name + " is ambiguous. Please provide a namespace.")
+		}
+
+		for _, v := range schemas {
+			return v, nil
+		}
+	}
+
+	// If this happens, that's very bad
+	return nil, BadRequestError("No schema lookup found for entity " + name)
+}
+
+// Lookup an entity set from the service metadata. Accepts a fully qualified
+// name, e.g., ODataService.ContainerName.EntitySetName,
+// ContainerName.EntitySetName or, if unambiguous, accepts a  simple identifier,
+// e.g., EntitySetName.
+func (service *GoDataService) LookupEntitySet(name string) (*GoDataEntitySet, error) {
+	parts := strings.Split(name, ".")
+	setName := parts[len(parts)-1]
+	// remove entity set from the list of parts
+	parts = parts[:len(parts)-1]
+
+	containers, ok := service.EntitySetLookup[setName]
+	if !ok {
+		return nil, BadRequestError("Entity set " + name + " does not exist.")
+	}
+
+	if len(parts) > 0 {
+		// container is provided
+		schemas, ok := containers[parts[len(parts)-1]]
+		if !ok {
+			return nil, BadRequestError("Container " + name + " not found.")
+		}
+
+		// remove container name from the list of parts
+		parts = parts[:len(parts)-1]
+
+		if len(parts) > 0 {
+			// schema is provided
+			set, ok := schemas[parts[len(parts)-1]]
+			if !ok {
+				return nil, BadRequestError("Entity set " + name + " not found.")
+			}
+			return set, nil
+		} else {
+			// no schema is provided
+
+			if len(schemas) > 1 {
+				// container is ambiguous
+				return nil, BadRequestError("Entity set " + name + " is ambiguous. Please provide fully qualified name.")
+			}
+
+			// there should be one schema, if not then something went horribly wrong
+			for _, set := range schemas {
+				return set, nil
+			}
+		}
+
+	} else {
+		// no container is provided
+
+		// return error if entity set is ambiguous
+		if len(containers) > 1 {
+			return nil, BadRequestError("Entity set " + name + " is ambiguous. Please provide fully qualified name.")
+		}
+
+		// find the first schema, it will be the only one
+		for _, schemas := range containers {
+			if len(schemas) > 1 {
+				// container is ambiguous
+				return nil, BadRequestError("Entity set " + name + " is ambiguous. Please provide fully qualified name.")
+			}
+
+			// there should be one schema, if not then something went horribly wrong
+			for _, set := range schemas {
+				return set, nil
+			}
+		}
+	}
+	return nil, BadRequestError("Entity set " + name + " not found.")
+}
@@ -0,0 +1,18 @@
+package godata
+
+import (
+	"context"
+	"strconv"
+)
+
+func ParseTopString(ctx context.Context, top string) (*GoDataTopQuery, error) {
+	i, err := strconv.Atoi(top)
+	result := GoDataTopQuery(i)
+	return &result, err
+}
+
+func ParseSkipString(ctx context.Context, skip string) (*GoDataSkipQuery, error) {
+	i, err := strconv.Atoi(skip)
+	result := GoDataSkipQuery(i)
+	return &result, err
+}
@@ -0,0 +1,409 @@
+package godata
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"strings"
+)
+
+// Parse a request from the HTTP server and format it into a GoDaataRequest type
+// to be passed to a provider to produce a result.
+func ParseRequest(ctx context.Context, path string, query url.Values) (*GoDataRequest, error) {
+	r := &GoDataRequest{
+		RequestKind: RequestKindUnknown,
+	}
+
+	if err := r.ParseUrlPath(path); err != nil {
+		return nil, err
+	}
+	if err := r.ParseUrlQuery(ctx, query); err != nil {
+		return nil, err
+	}
+	return r, nil
+}
+
+// Compare a request to a given service, and validate the semantics and update
+// the request with semantics included
+func (req *GoDataRequest) SemanticizeRequest(service *GoDataService) error {
+
+	// if request kind is a resource
+	for segment := req.FirstSegment; segment != nil; segment = segment.Next {
+		err := SemanticizePathSegment(segment, service)
+		if err != nil {
+			return err
+		}
+	}
+
+	switch req.LastSegment.SemanticReference.(type) {
+	case *GoDataEntitySet:
+		entitySet := req.LastSegment.SemanticReference.(*GoDataEntitySet)
+		entityType, err := service.LookupEntityType(entitySet.EntityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeFilterQuery(req.Query.Filter, service, entityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeExpandQuery(req.Query.Expand, service, entityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeSelectQuery(req.Query.Select, service, entityType)
+		if err != nil {
+			return err
+		}
+		err = SemanticizeOrderByQuery(req.Query.OrderBy, service, entityType)
+		if err != nil {
+			return err
+		}
+		// TODO: disallow invalid query params
+	case *GoDataEntityType:
+		entityType := req.LastSegment.SemanticReference.(*GoDataEntityType)
+		if err := SemanticizeExpandQuery(req.Query.Expand, service, entityType); err != nil {
+			return err
+		}
+		if err := SemanticizeSelectQuery(req.Query.Select, service, entityType); err != nil {
+			return err
+		}
+	}
+
+	if req.LastSegment.SemanticType == SemanticTypeMetadata {
+		req.RequestKind = RequestKindMetadata
+	} else if req.LastSegment.SemanticType == SemanticTypeRef {
+		req.RequestKind = RequestKindRef
+	} else if req.LastSegment.SemanticType == SemanticTypeEntitySet {
+		if req.LastSegment.Identifier == nil {
+			req.RequestKind = RequestKindCollection
+		} else {
+			req.RequestKind = RequestKindEntity
+		}
+	} else if req.LastSegment.SemanticType == SemanticTypeCount {
+		req.RequestKind = RequestKindCount
+	} else if req.FirstSegment == nil && req.LastSegment == nil {
+		req.RequestKind = RequestKindService
+	}
+
+	return nil
+}
+
+func (req *GoDataRequest) ParseUrlPath(path string) error {
+	parts := strings.Split(path, "/")
+	req.FirstSegment = &GoDataSegment{
+		RawValue:   parts[0],
+		Name:       ParseName(parts[0]),
+		Identifier: ParseIdentifiers(parts[0]),
+	}
+	currSegment := req.FirstSegment
+	for _, v := range parts[1:] {
+		temp := &GoDataSegment{
+			RawValue:   v,
+			Name:       ParseName(v),
+			Identifier: ParseIdentifiers(v),
+			Prev:       currSegment,
+		}
+		currSegment.Next = temp
+		currSegment = temp
+	}
+	req.LastSegment = currSegment
+
+	return nil
+}
+
+func SemanticizePathSegment(segment *GoDataSegment, service *GoDataService) error {
+	var err error
+
+	if segment.RawValue == "$metadata" {
+		if segment.Next != nil || segment.Prev != nil {
+			return BadRequestError("A metadata segment must be alone.")
+		}
+
+		segment.SemanticType = SemanticTypeMetadata
+		segment.SemanticReference = service.Metadata
+		return nil
+	}
+
+	if segment.RawValue == "$ref" {
+		// this is a ref segment
+		if segment.Next != nil {
+			return BadRequestError("A $ref segment must be last.")
+		}
+		if segment.Prev == nil {
+			return BadRequestError("A $ref segment must be preceded by something.")
+		}
+
+		segment.SemanticType = SemanticTypeRef
+		segment.SemanticReference = segment.Prev
+		return nil
+	}
+
+	if segment.RawValue == "$count" {
+		// this is a ref segment
+		if segment.Next != nil {
+			return BadRequestError("A $count segment must be last.")
+		}
+		if segment.Prev == nil {
+			return BadRequestError("A $count segment must be preceded by something.")
+		}
+
+		segment.SemanticType = SemanticTypeCount
+		segment.SemanticReference = segment.Prev
+		return nil
+	}
+
+	if _, ok := service.EntitySetLookup[segment.Name]; ok {
+		// this is an entity set
+		segment.SemanticType = SemanticTypeEntitySet
+		segment.SemanticReference, err = service.LookupEntitySet(segment.Name)
+		if err != nil {
+			return err
+		}
+
+		if segment.Prev == nil {
+			// this is the first segment
+			if segment.Next == nil {
+				// this is the only segment
+				return nil
+			} else {
+				// there is at least one more segment
+				if segment.Identifier != nil {
+					return BadRequestError("An entity set must be the last segment.")
+				}
+				// if it has an identifier, it is allowed
+				return nil
+			}
+		} else if segment.Next == nil {
+			// this is the last segment in a sequence of more than one
+			return nil
+		} else {
+			// this is a middle segment
+			if segment.Identifier != nil {
+				return BadRequestError("An entity set must be the last segment.")
+			}
+			// if it has an identifier, it is allowed
+			return nil
+		}
+	}
+
+	if segment.Prev != nil && segment.Prev.SemanticType == SemanticTypeEntitySet {
+		// previous segment was an entity set
+		semanticRef := segment.Prev.SemanticReference.(*GoDataEntitySet)
+
+		entity, err := service.LookupEntityType(semanticRef.EntityType)
+
+		if err != nil {
+			return err
+		}
+
+		for _, p := range entity.Properties {
+			if p.Name == segment.Name {
+				segment.SemanticType = SemanticTypeProperty
+				segment.SemanticReference = p
+				return nil
+			}
+		}
+
+		return BadRequestError("A valid entity property must follow entity set.")
+	}
+
+	return BadRequestError("Invalid segment " + segment.RawValue)
+}
+
+var supportedOdataKeywords = map[string]bool{
+	"$filter":      true,
+	"$apply":       true,
+	"$expand":      true,
+	"$select":      true,
+	"$orderby":     true,
+	"$top":         true,
+	"$skip":        true,
+	"$count":       true,
+	"$inlinecount": true,
+	"$search":      true,
+	"$compute":     true,
+	"$format":      true,
+	"at":           true,
+	"tags":         true,
+}
+
+type OdataComplianceConfig int
+
+const (
+	ComplianceStrict OdataComplianceConfig = 0
+	// Ignore duplicate ODATA keywords in the URL query.
+	ComplianceIgnoreDuplicateKeywords OdataComplianceConfig = 1 << iota
+	// Ignore unknown ODATA keywords in the URL query.
+	ComplianceIgnoreUnknownKeywords
+	// Ignore extraneous comma as the last character in a list of function arguments.
+	ComplianceIgnoreInvalidComma
+	ComplianceIgnoreAll OdataComplianceConfig = ComplianceIgnoreDuplicateKeywords |
+		ComplianceIgnoreUnknownKeywords |
+		ComplianceIgnoreInvalidComma
+)
+
+type parserConfigKey int
+
+const (
+	odataCompliance parserConfigKey = iota
+)
+
+// If the lenient mode is set, the 'failOnConfig' bits are used to determine the ODATA compliance.
+// This is mostly for historical reasons because the original parser had compliance issues.
+// If the lenient mode is not set, the parser returns an error.
+func WithOdataComplianceConfig(ctx context.Context, cfg OdataComplianceConfig) context.Context {
+	return context.WithValue(ctx, odataCompliance, cfg)
+}
+
+// ParseUrlQuery parses the URL query, applying optional logic specified in the context.
+func (req *GoDataRequest) ParseUrlQuery(ctx context.Context, query url.Values) error {
+	cfg, hasComplianceConfig := ctx.Value(odataCompliance).(OdataComplianceConfig)
+	if !hasComplianceConfig {
+		// Strict ODATA compliance by default.
+		cfg = ComplianceStrict
+	}
+	// Validate each query parameter is a valid ODATA keyword.
+	for key, val := range query {
+		if _, ok := supportedOdataKeywords[key]; !ok && (cfg&ComplianceIgnoreUnknownKeywords == 0) {
+			return BadRequestError(fmt.Sprintf("Query parameter '%s' is not supported", key)).
+				SetCause(&UnsupportedQueryParameterError{key})
+		}
+		if (cfg&ComplianceIgnoreDuplicateKeywords == 0) && (len(val) > 1) {
+			return BadRequestError(fmt.Sprintf("Query parameter '%s' cannot be specified more than once", key)).
+				SetCause(&DuplicateQueryParameterError{key})
+		}
+	}
+	filter := query.Get("$filter")
+	at := query.Get("at")
+	apply := query.Get("$apply")
+	expand := query.Get("$expand")
+	sel := query.Get("$select")
+	orderby := query.Get("$orderby")
+	top := query.Get("$top")
+	skip := query.Get("$skip")
+	count := query.Get("$count")
+	inlinecount := query.Get("$inlinecount")
+	search := query.Get("$search")
+	compute := query.Get("$compute")
+	format := query.Get("$format")
+
+	result := &GoDataQuery{}
+
+	var err error = nil
+	if filter != "" {
+		result.Filter, err = ParseFilterString(ctx, filter)
+	}
+	if err != nil {
+		return err
+	}
+	if at != "" {
+		result.At, err = ParseFilterString(ctx, at)
+	}
+	if err != nil {
+		return err
+	}
+	if at != "" {
+		result.At, err = ParseFilterString(ctx, at)
+	}
+	if err != nil {
+		return err
+	}
+	if apply != "" {
+		result.Apply, err = ParseApplyString(ctx, apply)
+	}
+	if err != nil {
+		return err
+	}
+	if expand != "" {
+		result.Expand, err = ParseExpandString(ctx, expand)
+	}
+	if err != nil {
+		return err
+	}
+	if sel != "" {
+		result.Select, err = ParseSelectString(ctx, sel)
+	}
+	if err != nil {
+		return err
+	}
+	if orderby != "" {
+		result.OrderBy, err = ParseOrderByString(ctx, orderby)
+	}
+	if err != nil {
+		return err
+	}
+	if top != "" {
+		result.Top, err = ParseTopString(ctx, top)
+	}
+	if err != nil {
+		return err
+	}
+	if skip != "" {
+		result.Skip, err = ParseSkipString(ctx, skip)
+	}
+	if err != nil {
+		return err
+	}
+	if count != "" {
+		result.Count, err = ParseCountString(ctx, count)
+	}
+	if err != nil {
+		return err
+	}
+	if inlinecount != "" {
+		result.InlineCount, err = ParseInlineCountString(ctx, inlinecount)
+	}
+	if err != nil {
+		return err
+	}
+	if search != "" {
+		result.Search, err = ParseSearchString(ctx, search)
+	}
+	if err != nil {
+		return err
+	}
+	if compute != "" {
+		result.Compute, err = ParseComputeString(ctx, compute)
+	}
+	if err != nil {
+		return err
+	}
+	if format != "" {
+		err = NotImplementedError("Format is not supported")
+	}
+	if err != nil {
+		return err
+	}
+	req.Query = result
+	return err
+}
+
+func ParseIdentifiers(segment string) *GoDataIdentifier {
+	if !(strings.Contains(segment, "(") && strings.Contains(segment, ")")) {
+		return nil
+	}
+
+	rawIds := segment[strings.LastIndex(segment, "(")+1 : strings.LastIndex(segment, ")")]
+	parts := strings.Split(rawIds, ",")
+
+	result := make(GoDataIdentifier)
+
+	for _, v := range parts {
+		if strings.Contains(v, "=") {
+			split := strings.SplitN(v, "=", 2)
+			result[split[0]] = split[1]
+		} else {
+			result[v] = ""
+		}
+	}
+
+	return &result
+}
+
+func ParseName(segment string) string {
+	if strings.Contains(segment, "(") {
+		return segment[:strings.LastIndex(segment, "(")]
+	} else {
+		return segment
+	}
+}
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2022 Geon Kim
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
@@ -0,0 +1,441 @@
+package memlimit
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"os"
+	"path/filepath"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+var (
+	// ErrNoCgroup is returned when the process is not in cgroup.
+	ErrNoCgroup = errors.New("process is not in cgroup")
+	// ErrCgroupsNotSupported is returned when the system does not support cgroups.
+	ErrCgroupsNotSupported = errors.New("cgroups is not supported on this system")
+)
+
+// fromCgroup retrieves the memory limit from the cgroup.
+// The versionDetector function is used to detect the cgroup version from the mountinfo.
+func fromCgroup(versionDetector func(mis []mountInfo) (bool, bool)) (uint64, error) {
+	mf, err := os.Open("/proc/self/mountinfo")
+	if err != nil {
+		return 0, fmt.Errorf("failed to open /proc/self/mountinfo: %w", err)
+	}
+	defer mf.Close()
+
+	mis, err := parseMountInfo(mf)
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse mountinfo: %w", err)
+	}
+
+	v1, v2 := versionDetector(mis)
+	if !(v1 || v2) {
+		return 0, ErrNoCgroup
+	}
+
+	cf, err := os.Open("/proc/self/cgroup")
+	if err != nil {
+		return 0, fmt.Errorf("failed to open /proc/self/cgroup: %w", err)
+	}
+	defer cf.Close()
+
+	chs, err := parseCgroupFile(cf)
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse cgroup file: %w", err)
+	}
+
+	if v2 {
+		limit, err := getMemoryLimitV2(chs, mis)
+		if err == nil {
+			return limit, nil
+		} else if !v1 {
+			return 0, err
+		}
+	}
+
+	return getMemoryLimitV1(chs, mis)
+}
+
+// detectCgroupVersion detects the cgroup version from the mountinfo.
+func detectCgroupVersion(mis []mountInfo) (bool, bool) {
+	var v1, v2 bool
+	for _, mi := range mis {
+		switch mi.FilesystemType {
+		case "cgroup":
+			v1 = true
+		case "cgroup2":
+			v2 = true
+		}
+	}
+	return v1, v2
+}
+
+// getMemoryLimitV2 retrieves the memory limit from the cgroup v2 controller.
+func getMemoryLimitV2(chs []cgroupHierarchy, mis []mountInfo) (uint64, error) {
+	// find the cgroup v2 path for the memory controller.
+	// in cgroup v2, the paths are unified and the controller list is empty.
+	idx := slices.IndexFunc(chs, func(ch cgroupHierarchy) bool {
+		return ch.HierarchyID == "0" && ch.ControllerList == ""
+	})
+	if idx == -1 {
+		return 0, errors.New("cgroup v2 path not found")
+	}
+	relPath := chs[idx].CgroupPath
+
+	// find the mountpoint for the cgroup v2 controller.
+	idx = slices.IndexFunc(mis, func(mi mountInfo) bool {
+		return mi.FilesystemType == "cgroup2"
+	})
+	if idx == -1 {
+		return 0, errors.New("cgroup v2 mountpoint not found")
+	}
+	root, mountPoint := mis[idx].Root, mis[idx].MountPoint
+
+	// resolve the actual cgroup path
+	cgroupPath, err := resolveCgroupPath(mountPoint, root, relPath)
+	if err != nil {
+		return 0, err
+	}
+
+	// retrieve the memory limit from the memory.max recursively.
+	return walkCgroupV2Hierarchy(cgroupPath, mountPoint)
+}
+
+// readMemoryLimitV2FromPath reads the memory limit for cgroup v2 from the given path.
+// this function expects the path to be memory.max file.
+func readMemoryLimitV2FromPath(path string) (uint64, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return 0, ErrNoLimit
+		}
+		return 0, fmt.Errorf("failed to read memory.max: %w", err)
+	}
+
+	slimit := strings.TrimSpace(string(b))
+	if slimit == "max" {
+		return 0, ErrNoLimit
+	}
+
+	limit, err := strconv.ParseUint(slimit, 10, 64)
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse memory.max value: %w", err)
+	}
+
+	return limit, nil
+}
+
+// walkCgroupV2Hierarchy walks up the cgroup v2 hierarchy to find the most restrictive memory limit.
+func walkCgroupV2Hierarchy(cgroupPath, mountPoint string) (uint64, error) {
+	var (
+		found              = false
+		minLimit    uint64 = math.MaxUint64
+		currentPath        = cgroupPath
+	)
+	for {
+		limit, err := readMemoryLimitV2FromPath(filepath.Join(currentPath, "memory.max"))
+		if err != nil && !errors.Is(err, ErrNoLimit) {
+			return 0, err
+		} else if err == nil {
+			found = true
+			minLimit = min(minLimit, limit)
+		}
+
+		if currentPath == mountPoint {
+			break
+		}
+
+		parent := filepath.Dir(currentPath)
+		if parent == currentPath {
+			break
+		}
+		currentPath = parent
+	}
+	if !found {
+		return 0, ErrNoLimit
+	}
+
+	return minLimit, nil
+}
+
+// getMemoryLimitV1 retrieves the memory limit from the cgroup v1 controller.
+func getMemoryLimitV1(chs []cgroupHierarchy, mis []mountInfo) (uint64, error) {
+	// find the cgroup v1 path for the memory controller.
+	idx := slices.IndexFunc(chs, func(ch cgroupHierarchy) bool {
+		return slices.Contains(strings.Split(ch.ControllerList, ","), "memory")
+	})
+	if idx == -1 {
+		return 0, errors.New("cgroup v1 path for memory controller not found")
+	}
+	relPath := chs[idx].CgroupPath
+
+	// find the mountpoint for the cgroup v1 controller.
+	idx = slices.IndexFunc(mis, func(mi mountInfo) bool {
+		return mi.FilesystemType == "cgroup" && slices.Contains(strings.Split(mi.SuperOptions, ","), "memory")
+	})
+	if idx == -1 {
+		return 0, errors.New("cgroup v1 mountpoint for memory controller not found")
+	}
+	root, mountPoint := mis[idx].Root, mis[idx].MountPoint
+
+	// resolve the actual cgroup path
+	cgroupPath, err := resolveCgroupPath(mountPoint, root, relPath)
+	if err != nil {
+		return 0, err
+	}
+
+	// retrieve the memory limit from the memory.stat and memory.limit_in_bytes files.
+	return readMemoryLimitV1FromPath(cgroupPath)
+}
+
+// getCgroupV1NoLimit returns the maximum value that is used to represent no limit in cgroup v1.
+// the max memory limit is max int64, but it should be multiple of the page size.
+func getCgroupV1NoLimit() uint64 {
+	ps := uint64(os.Getpagesize())
+	return math.MaxInt64 / ps * ps
+}
+
+// readMemoryLimitV1FromPath reads the memory limit for cgroup v1 from the given path.
+// this function expects the path to be the cgroup directory.
+func readMemoryLimitV1FromPath(cgroupPath string) (uint64, error) {
+	// read hierarchical_memory_limit and memory.limit_in_bytes files.
+	// but if hierarchical_memory_limit is not available, then use the max value as a fallback.
+	hml, err := readHierarchicalMemoryLimit(filepath.Join(cgroupPath, "memory.stat"))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return 0, fmt.Errorf("failed to read hierarchical_memory_limit: %w", err)
+	} else if hml == 0 {
+		hml = math.MaxUint64
+	}
+
+	// read memory.limit_in_bytes file.
+	b, err := os.ReadFile(filepath.Join(cgroupPath, "memory.limit_in_bytes"))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return 0, fmt.Errorf("failed to read memory.limit_in_bytes: %w", err)
+	}
+	lib, err := strconv.ParseUint(strings.TrimSpace(string(b)), 10, 64)
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse memory.limit_in_bytes value: %w", err)
+	} else if lib == 0 {
+		hml = math.MaxUint64
+	}
+
+	// use the minimum value between hierarchical_memory_limit and memory.limit_in_bytes.
+	// if the limit is the maximum value, then it is considered as no limit.
+	limit := min(hml, lib)
+	if limit >= getCgroupV1NoLimit() {
+		return 0, ErrNoLimit
+	}
+
+	return limit, nil
+}
+
+// readHierarchicalMemoryLimit extracts hierarchical_memory_limit from memory.stat.
+// this function expects the path to be memory.stat file.
+func readHierarchicalMemoryLimit(path string) (uint64, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return 0, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		fields := strings.Split(line, " ")
+		if len(fields) < 2 {
+			return 0, fmt.Errorf("failed to parse memory.stat %q: not enough fields", line)
+		}
+
+		if fields[0] == "hierarchical_memory_limit" {
+			if len(fields) > 2 {
+				return 0, fmt.Errorf("failed to parse memory.stat %q: too many fields for hierarchical_memory_limit", line)
+			}
+			return strconv.ParseUint(fields[1], 10, 64)
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return 0, err
+	}
+
+	return 0, nil
+}
+
+// https://www.man7.org/linux/man-pages/man5/proc_pid_mountinfo.5.html
+// 731 771 0:59 /sysrq-trigger /proc/sysrq-trigger ro,nosuid,nodev,noexec,relatime - proc proc rw
+//
+// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
+// (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
+//
+// (1)  mount ID: a unique ID for the mount (may be reused after umount(2)).
+// (2)  parent ID: the ID of the parent mount (or of self for the root of this mount namespace's mount tree).
+// (3)  major:minor: the value of st_dev for files on this filesystem (see stat(2)).
+// (4)  root: the pathname of the directory in the filesystem which forms the root of this mount.
+// (5)  mount point: the pathname of the mount point relative to the process's root directory.
+// (6)  mount options: per-mount options (see mount(2)).
+// (7)  optional fields: zero or more fields of the form "tag[:value]"; see below.
+// (8)  separator: the end of the optional fields is marked by a single hyphen.
+// (9)  filesystem type: the filesystem type in the form "type[.subtype]".
+// (10) mount source: filesystem-specific information or "none".
+// (11) super options: per-superblock options (see mount(2)).
+type mountInfo struct {
+	Root           string
+	MountPoint     string
+	FilesystemType string
+	SuperOptions   string
+}
+
+// parseMountInfoLine parses a line from the mountinfo file.
+func parseMountInfoLine(line string) (mountInfo, error) {
+	if line == "" {
+		return mountInfo{}, errors.New("empty line")
+	}
+
+	fieldss := strings.SplitN(line, " - ", 2)
+	if len(fieldss) != 2 {
+		return mountInfo{}, fmt.Errorf("invalid separator")
+	}
+
+	fields1 := strings.SplitN(fieldss[0], " ", 7)
+	if len(fields1) < 6 {
+		return mountInfo{}, fmt.Errorf("not enough fields before separator: %v", fields1)
+	} else if len(fields1) == 6 {
+		fields1 = append(fields1, "")
+	}
+
+	fields2 := strings.SplitN(fieldss[1], " ", 3)
+	if len(fields2) < 3 {
+		return mountInfo{}, fmt.Errorf("not enough fields after separator: %v", fields2)
+	}
+
+	return mountInfo{
+		Root:           fields1[3],
+		MountPoint:     fields1[4],
+		FilesystemType: fields2[0],
+		SuperOptions:   fields2[2],
+	}, nil
+}
+
+// parseMountInfo parses the mountinfo file.
+func parseMountInfo(r io.Reader) ([]mountInfo, error) {
+	var (
+		s   = bufio.NewScanner(r)
+		mis []mountInfo
+	)
+	for s.Scan() {
+		line := s.Text()
+
+		mi, err := parseMountInfoLine(line)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse mountinfo file %q: %w", line, err)
+		}
+
+		mis = append(mis, mi)
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+
+	return mis, nil
+}
+
+// https://www.man7.org/linux/man-pages/man7/cgroups.7.html
+//
+// 5:cpuacct,cpu,cpuset:/daemons
+// (1)       (2)           (3)
+//
+// (1) hierarchy ID:
+//
+//	cgroups version 1 hierarchies, this field
+//	contains a unique hierarchy ID number that can be
+//	matched to a hierarchy ID in /proc/cgroups.  For the
+//	cgroups version 2 hierarchy, this field contains the
+//	value 0.
+//
+// (2) controller list:
+//
+//	For cgroups version 1 hierarchies, this field
+//	contains a comma-separated list of the controllers
+//	bound to the hierarchy.  For the cgroups version 2
+//	hierarchy, this field is empty.
+//
+// (3) cgroup path:
+//
+//	This field contains the pathname of the control group
+//	in the hierarchy to which the process belongs.  This
+//	pathname is relative to the mount point of the
+//	hierarchy.
+type cgroupHierarchy struct {
+	HierarchyID    string
+	ControllerList string
+	CgroupPath     string
+}
+
+// parseCgroupHierarchyLine parses a line from the cgroup file.
+func parseCgroupHierarchyLine(line string) (cgroupHierarchy, error) {
+	if line == "" {
+		return cgroupHierarchy{}, errors.New("empty line")
+	}
+
+	fields := strings.Split(line, ":")
+	if len(fields) < 3 {
+		return cgroupHierarchy{}, fmt.Errorf("not enough fields: %v", fields)
+	} else if len(fields) > 3 {
+		return cgroupHierarchy{}, fmt.Errorf("too many fields: %v", fields)
+	}
+
+	return cgroupHierarchy{
+		HierarchyID:    fields[0],
+		ControllerList: fields[1],
+		CgroupPath:     fields[2],
+	}, nil
+}
+
+// parseCgroupFile parses the cgroup file.
+func parseCgroupFile(r io.Reader) ([]cgroupHierarchy, error) {
+	var (
+		s   = bufio.NewScanner(r)
+		chs []cgroupHierarchy
+	)
+	for s.Scan() {
+		line := s.Text()
+
+		ch, err := parseCgroupHierarchyLine(line)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse cgroup file %q: %w", line, err)
+		}
+
+		chs = append(chs, ch)
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+
+	return chs, nil
+}
+
+// resolveCgroupPath resolves the actual cgroup path from the mountpoint, root, and cgroupRelPath.
+func resolveCgroupPath(mountpoint, root, cgroupRelPath string) (string, error) {
+	rel, err := filepath.Rel(root, cgroupRelPath)
+	if err != nil {
+		return "", err
+	}
+
+	// if the relative path is ".", then the cgroupRelPath is the root itself.
+	if rel == "." {
+		return mountpoint, nil
+	}
+
+	// if the relative path starts with "..", then it is outside the root.
+	if strings.HasPrefix(rel, "..") {
+		return "", fmt.Errorf("invalid cgroup path: %s is not under root %s", cgroupRelPath, root)
+	}
+
+	return filepath.Join(mountpoint, rel), nil
+}
@@ -0,0 +1,32 @@
+//go:build linux
+// +build linux
+
+package memlimit
+
+// FromCgroup retrieves the memory limit from the cgroup.
+func FromCgroup() (uint64, error) {
+	return fromCgroup(detectCgroupVersion)
+}
+
+// FromCgroupV1 retrieves the memory limit from the cgroup v1 controller.
+// After v1.0.0, this function could be removed and FromCgroup should be used instead.
+func FromCgroupV1() (uint64, error) {
+	return fromCgroup(func(_ []mountInfo) (bool, bool) {
+		return true, false
+	})
+}
+
+// FromCgroupHybrid retrieves the memory limit from the cgroup v2 and v1 controller sequentially,
+// basically, it is equivalent to FromCgroup.
+// After v1.0.0, this function could be removed and FromCgroup should be used instead.
+func FromCgroupHybrid() (uint64, error) {
+	return FromCgroup()
+}
+
+// FromCgroupV2 retrieves the memory limit from the cgroup v2 controller.
+// After v1.0.0, this function could be removed and FromCgroup should be used instead.
+func FromCgroupV2() (uint64, error) {
+	return fromCgroup(func(_ []mountInfo) (bool, bool) {
+		return false, true
+	})
+}
@@ -0,0 +1,20 @@
+//go:build !linux
+// +build !linux
+
+package memlimit
+
+func FromCgroup() (uint64, error) {
+	return 0, ErrCgroupsNotSupported
+}
+
+func FromCgroupV1() (uint64, error) {
+	return 0, ErrCgroupsNotSupported
+}
+
+func FromCgroupHybrid() (uint64, error) {
+	return 0, ErrCgroupsNotSupported
+}
+
+func FromCgroupV2() (uint64, error) {
+	return 0, ErrCgroupsNotSupported
+}
@@ -0,0 +1,14 @@
+package memlimit
+
+import (
+	"github.com/pbnjay/memory"
+)
+
+// FromSystem returns the total memory of the system.
+func FromSystem() (uint64, error) {
+	limit := memory.TotalMemory()
+	if limit == 0 {
+		return 0, ErrNoLimit
+	}
+	return limit, nil
+}
@@ -0,0 +1,59 @@
+package memlimit
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+	"strings"
+)
+
+const (
+	envAUTOMEMLIMIT_EXPERIMENT = "AUTOMEMLIMIT_EXPERIMENT"
+)
+
+// Experiments is a set of experiment flags.
+// It is used to enable experimental features.
+//
+// You can set the flags by setting the environment variable AUTOMEMLIMIT_EXPERIMENT.
+// The value of the environment variable is a comma-separated list of experiment names.
+//
+// The following experiment names are known:
+//
+//   - none: disable all experiments
+//   - system: enable fallback to system memory limit
+type Experiments struct {
+	// System enables fallback to system memory limit.
+	System bool
+}
+
+func parseExperiments() (Experiments, error) {
+	var exp Experiments
+
+	// Create a map of known experiment names.
+	names := make(map[string]func(bool))
+	rv := reflect.ValueOf(&exp).Elem()
+	rt := rv.Type()
+	for i := 0; i < rt.NumField(); i++ {
+		field := rv.Field(i)
+		names[strings.ToLower(rt.Field(i).Name)] = field.SetBool
+	}
+
+	// Parse names.
+	for _, f := range strings.Split(os.Getenv(envAUTOMEMLIMIT_EXPERIMENT), ",") {
+		if f == "" {
+			continue
+		}
+		if f == "none" {
+			exp = Experiments{}
+			continue
+		}
+		val := true
+		set, ok := names[f]
+		if !ok {
+			return Experiments{}, fmt.Errorf("unknown AUTOMEMLIMIT_EXPERIMENT %s", f)
+		}
+		set(val)
+	}
+
+	return exp, nil
+}
@@ -0,0 +1,13 @@
+package memlimit
+
+import (
+	"context"
+	"log/slog"
+)
+
+type noopLogger struct{}
+
+func (noopLogger) Enabled(context.Context, slog.Level) bool  { return false }
+func (noopLogger) Handle(context.Context, slog.Record) error { return nil }
+func (d noopLogger) WithAttrs([]slog.Attr) slog.Handler      { return d }
+func (d noopLogger) WithGroup(string) slog.Handler           { return d }
@@ -0,0 +1,285 @@
+package memlimit
+
+import (
+	"errors"
+	"fmt"
+	"log/slog"
+	"math"
+	"os"
+	"runtime/debug"
+	"strconv"
+	"time"
+)
+
+const (
+	envGOMEMLIMIT   = "GOMEMLIMIT"
+	envAUTOMEMLIMIT = "AUTOMEMLIMIT"
+	// Deprecated: use memlimit.WithLogger instead
+	envAUTOMEMLIMIT_DEBUG = "AUTOMEMLIMIT_DEBUG"
+
+	defaultAUTOMEMLIMIT = 0.9
+)
+
+// ErrNoLimit is returned when the memory limit is not set.
+var ErrNoLimit = errors.New("memory is not limited")
+
+type config struct {
+	logger   *slog.Logger
+	ratio    float64
+	provider Provider
+	refresh  time.Duration
+}
+
+// Option is a function that configures the behavior of SetGoMemLimitWithOptions.
+type Option func(cfg *config)
+
+// WithRatio configures the ratio of the memory limit to set as GOMEMLIMIT.
+//
+// Default: 0.9
+func WithRatio(ratio float64) Option {
+	return func(cfg *config) {
+		cfg.ratio = ratio
+	}
+}
+
+// WithProvider configures the provider.
+//
+// Default: FromCgroup
+func WithProvider(provider Provider) Option {
+	return func(cfg *config) {
+		cfg.provider = provider
+	}
+}
+
+// WithLogger configures the logger.
+// It automatically attaches the "package" attribute to the logs.
+//
+// Default: slog.New(noopLogger{})
+func WithLogger(logger *slog.Logger) Option {
+	return func(cfg *config) {
+		cfg.logger = memlimitLogger(logger)
+	}
+}
+
+// WithRefreshInterval configures the refresh interval for automemlimit.
+// If a refresh interval is greater than 0, automemlimit periodically fetches
+// the memory limit from the provider and reapplies it if it has changed.
+// If the provider returns an error, it logs the error and continues.
+// ErrNoLimit is treated as math.MaxInt64.
+//
+// Default: 0 (no refresh)
+func WithRefreshInterval(refresh time.Duration) Option {
+	return func(cfg *config) {
+		cfg.refresh = refresh
+	}
+}
+
+// WithEnv configures whether to use environment variables.
+//
+// Default: false
+//
+// Deprecated: currently this does nothing.
+func WithEnv() Option {
+	return func(cfg *config) {}
+}
+
+func memlimitLogger(logger *slog.Logger) *slog.Logger {
+	if logger == nil {
+		return slog.New(noopLogger{})
+	}
+	return logger.With(slog.String("package", "github.com/KimMachineGun/automemlimit/memlimit"))
+}
+
+// SetGoMemLimitWithOpts sets GOMEMLIMIT with options and environment variables.
+//
+// You can configure how much memory of the cgroup's memory limit to set as GOMEMLIMIT
+// through AUTOMEMLIMIT environment variable in the half-open range (0.0,1.0].
+//
+// If AUTOMEMLIMIT is not set, it defaults to 0.9. (10% is the headroom for memory sources the Go runtime is unaware of.)
+// If GOMEMLIMIT is already set or AUTOMEMLIMIT=off, this function does nothing.
+//
+// If AUTOMEMLIMIT_EXPERIMENT is set, it enables experimental features.
+// Please see the documentation of Experiments for more details.
+//
+// Options:
+//   - WithRatio
+//   - WithProvider
+//   - WithLogger
+func SetGoMemLimitWithOpts(opts ...Option) (_ int64, _err error) {
+	// init config
+	cfg := &config{
+		logger:   slog.New(noopLogger{}),
+		ratio:    defaultAUTOMEMLIMIT,
+		provider: FromCgroup,
+	}
+	// TODO: remove this
+	if debug, ok := os.LookupEnv(envAUTOMEMLIMIT_DEBUG); ok {
+		defaultLogger := memlimitLogger(slog.Default())
+		defaultLogger.Warn("AUTOMEMLIMIT_DEBUG is deprecated, use memlimit.WithLogger instead")
+		if debug == "true" {
+			cfg.logger = defaultLogger
+		}
+	}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+
+	// log error if any on return
+	defer func() {
+		if _err != nil {
+			cfg.logger.Error("failed to set GOMEMLIMIT", slog.Any("error", _err))
+		}
+	}()
+
+	// parse experiments
+	exps, err := parseExperiments()
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse experiments: %w", err)
+	}
+	if exps.System {
+		cfg.logger.Info("system experiment is enabled: using system memory limit as a fallback")
+		cfg.provider = ApplyFallback(cfg.provider, FromSystem)
+	}
+
+	// rollback to previous memory limit on panic
+	snapshot := debug.SetMemoryLimit(-1)
+	defer rollbackOnPanic(cfg.logger, snapshot, &_err)
+
+	// check if GOMEMLIMIT is already set
+	if val, ok := os.LookupEnv(envGOMEMLIMIT); ok {
+		cfg.logger.Info("GOMEMLIMIT is already set, skipping", slog.String(envGOMEMLIMIT, val))
+		return 0, nil
+	}
+
+	// parse AUTOMEMLIMIT
+	ratio := cfg.ratio
+	if val, ok := os.LookupEnv(envAUTOMEMLIMIT); ok {
+		if val == "off" {
+			cfg.logger.Info("AUTOMEMLIMIT is set to off, skipping")
+			return 0, nil
+		}
+		ratio, err = strconv.ParseFloat(val, 64)
+		if err != nil {
+			return 0, fmt.Errorf("cannot parse AUTOMEMLIMIT: %s", val)
+		}
+	}
+
+	// apply ratio to the provider
+	provider := capProvider(ApplyRatio(cfg.provider, ratio))
+
+	// set the memory limit and start refresh
+	limit, err := updateGoMemLimit(uint64(snapshot), provider, cfg.logger)
+	refresh(provider, cfg.logger, cfg.refresh)
+	if err != nil {
+		if errors.Is(err, ErrNoLimit) {
+			cfg.logger.Info("memory is not limited, skipping")
+			// TODO: consider returning the snapshot
+			return 0, nil
+		}
+		return 0, fmt.Errorf("failed to set GOMEMLIMIT: %w", err)
+	}
+
+	return int64(limit), nil
+}
+
+// updateGoMemLimit updates the Go's memory limit, if it has changed.
+func updateGoMemLimit(currLimit uint64, provider Provider, logger *slog.Logger) (uint64, error) {
+	newLimit, err := provider()
+	if err != nil {
+		return 0, err
+	}
+
+	if newLimit == currLimit {
+		logger.Debug("GOMEMLIMIT is not changed, skipping", slog.Uint64(envGOMEMLIMIT, newLimit))
+		return newLimit, nil
+	}
+
+	debug.SetMemoryLimit(int64(newLimit))
+	logger.Info("GOMEMLIMIT is updated", slog.Uint64(envGOMEMLIMIT, newLimit), slog.Uint64("previous", currLimit))
+
+	return newLimit, nil
+}
+
+// refresh spawns a goroutine that runs every refresh duration and updates the GOMEMLIMIT if it has changed.
+// See more details in the documentation of WithRefreshInterval.
+func refresh(provider Provider, logger *slog.Logger, refresh time.Duration) {
+	if refresh == 0 {
+		return
+	}
+
+	provider = noErrNoLimitProvider(provider)
+
+	t := time.NewTicker(refresh)
+	go func() {
+		for range t.C {
+			err := func() (_err error) {
+				snapshot := debug.SetMemoryLimit(-1)
+				defer rollbackOnPanic(logger, snapshot, &_err)
+
+				_, err := updateGoMemLimit(uint64(snapshot), provider, logger)
+				if err != nil {
+					return err
+				}
+
+				return nil
+			}()
+			if err != nil {
+				logger.Error("failed to refresh GOMEMLIMIT", slog.Any("error", err))
+			}
+		}
+	}()
+}
+
+// rollbackOnPanic rollbacks to the snapshot on panic.
+// Since it uses recover, it should be called in a deferred function.
+func rollbackOnPanic(logger *slog.Logger, snapshot int64, err *error) {
+	panicErr := recover()
+	if panicErr != nil {
+		if *err != nil {
+			logger.Error("failed to set GOMEMLIMIT", slog.Any("error", *err))
+		}
+		*err = fmt.Errorf("panic during setting the Go's memory limit, rolling back to previous limit %d: %v",
+			snapshot, panicErr,
+		)
+		debug.SetMemoryLimit(snapshot)
+	}
+}
+
+// SetGoMemLimitWithEnv sets GOMEMLIMIT with the value from the environment variables.
+// Since WithEnv is deprecated, this function is equivalent to SetGoMemLimitWithOpts().
+// Deprecated: use SetGoMemLimitWithOpts instead.
+func SetGoMemLimitWithEnv() {
+	_, _ = SetGoMemLimitWithOpts()
+}
+
+// SetGoMemLimit sets GOMEMLIMIT with the value from the cgroup's memory limit and given ratio.
+func SetGoMemLimit(ratio float64) (int64, error) {
+	return SetGoMemLimitWithOpts(WithRatio(ratio))
+}
+
+// SetGoMemLimitWithProvider sets GOMEMLIMIT with the value from the given provider and ratio.
+func SetGoMemLimitWithProvider(provider Provider, ratio float64) (int64, error) {
+	return SetGoMemLimitWithOpts(WithProvider(provider), WithRatio(ratio))
+}
+
+func noErrNoLimitProvider(provider Provider) Provider {
+	return func() (uint64, error) {
+		limit, err := provider()
+		if errors.Is(err, ErrNoLimit) {
+			return math.MaxInt64, nil
+		}
+		return limit, err
+	}
+}
+
+func capProvider(provider Provider) Provider {
+	return func() (uint64, error) {
+		limit, err := provider()
+		if err != nil {
+			return 0, err
+		} else if limit > math.MaxInt64 {
+			return math.MaxInt64, nil
+		}
+		return limit, nil
+	}
+}
@@ -0,0 +1,43 @@
+package memlimit
+
+import (
+	"fmt"
+)
+
+// Provider is a function that returns the memory limit.
+type Provider func() (uint64, error)
+
+// Limit is a helper Provider function that returns the given limit.
+func Limit(limit uint64) func() (uint64, error) {
+	return func() (uint64, error) {
+		return limit, nil
+	}
+}
+
+// ApplyRationA is a helper Provider function that applies the given ratio to the given provider.
+func ApplyRatio(provider Provider, ratio float64) Provider {
+	if ratio == 1 {
+		return provider
+	}
+	return func() (uint64, error) {
+		if ratio <= 0 || ratio > 1 {
+			return 0, fmt.Errorf("invalid ratio: %f, ratio should be in the range (0.0,1.0]", ratio)
+		}
+		limit, err := provider()
+		if err != nil {
+			return 0, err
+		}
+		return uint64(float64(limit) * ratio), nil
+	}
+}
+
+// ApplyFallback is a helper Provider function that sets the fallback provider.
+func ApplyFallback(provider Provider, fallback Provider) Provider {
+	return func() (uint64, error) {
+		limit, err := provider()
+		if err != nil {
+			return fallback()
+		}
+		return limit, nil
+	}
+}
@@ -0,0 +1,18 @@
+language: go
+
+go:
+  - 1.6
+  - 1.7
+  - 1.8
+  - tip
+
+script:
+  - go test -v
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/06e3328629952dabe3e0
+    on_success: change  # options: [always|never|change] default: always
+    on_failure: always  # options: [always|never|change] default: always
+    on_start: never     # options: [always|never|change] default: always
@@ -0,0 +1,8 @@
+# 1.0.1 (2017-05-31)
+
+## Fixed
+- #21: Fix generation of alphanumeric strings (thanks @dbarranco)
+
+# 1.0.0 (2014-04-30)
+
+- Initial release.
@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
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+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
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+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
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+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
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+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
@@ -0,0 +1,70 @@
+GoUtils
+===========
+[![Stability: Maintenance](https://masterminds.github.io/stability/maintenance.svg)](https://masterminds.github.io/stability/maintenance.html)
+[![GoDoc](https://godoc.org/github.com/Masterminds/goutils?status.png)](https://godoc.org/github.com/Masterminds/goutils) [![Build Status](https://travis-ci.org/Masterminds/goutils.svg?branch=master)](https://travis-ci.org/Masterminds/goutils) [![Build status](https://ci.appveyor.com/api/projects/status/sc2b1ew0m7f0aiju?svg=true)](https://ci.appveyor.com/project/mattfarina/goutils)
+
+
+GoUtils provides users with utility functions to manipulate strings in various ways. It is a Go implementation of some
+string manipulation libraries of Java Apache Commons. GoUtils includes the following Java Apache Commons classes:
+* WordUtils    
+* RandomStringUtils  
+* StringUtils (partial implementation)
+
+## Installation
+If you have Go set up on your system, from the GOPATH directory within the command line/terminal, enter this:
+
+	go get github.com/Masterminds/goutils
+
+If you do not have Go set up on your system, please follow the [Go installation directions from the documenation](http://golang.org/doc/install), and then follow the instructions above to install GoUtils.
+
+
+## Documentation
+GoUtils doc is available here: [![GoDoc](https://godoc.org/github.com/Masterminds/goutils?status.png)](https://godoc.org/github.com/Masterminds/goutils)
+
+
+## Usage
+The code snippets below show examples of how to use GoUtils. Some functions return errors while others do not. The first instance below, which does not return an error, is the `Initials` function (located within the `wordutils.go` file).
+
+    package main
+
+    import (
+        "fmt"
+    	"github.com/Masterminds/goutils"
+    )
+
+    func main() {
+
+    	// EXAMPLE 1: A goutils function which returns no errors
+        fmt.Println (goutils.Initials("John Doe Foo")) // Prints out "JDF"
+
+    }
+Some functions return errors mainly due to illegal arguements used as parameters. The code example below illustrates how to deal with function that returns an error. In this instance, the function is the `Random` function (located within the `randomstringutils.go` file).
+
+    package main
+
+    import (
+        "fmt"
+        "github.com/Masterminds/goutils"
+    )
+
+    func main() {
+
+        // EXAMPLE 2: A goutils function which returns an error
+        rand1, err1 := goutils.Random (-1, 0, 0, true, true)  
+
+        if err1 != nil {
+			fmt.Println(err1) // Prints out error message because -1 was entered as the first parameter in goutils.Random(...)
+		} else {
+			fmt.Println(rand1)
+		}
+
+    }
+
+## License
+GoUtils is licensed under the Apache License, Version 2.0. Please check the LICENSE.txt file or visit http://www.apache.org/licenses/LICENSE-2.0 for a copy of the license.
+
+## Issue Reporting
+Make suggestions or report issues using the Git issue tracker: https://github.com/Masterminds/goutils/issues
+
+## Website
+* [GoUtils webpage](http://Masterminds.github.io/goutils/)
@@ -0,0 +1,21 @@
+version: build-{build}.{branch}
+
+clone_folder: C:\gopath\src\github.com\Masterminds\goutils
+shallow_clone: true
+
+environment:
+  GOPATH: C:\gopath
+
+platform:
+  - x64
+
+build: off
+
+install:
+  - go version
+  - go env
+
+test_script:
+  - go test -v
+
+deploy: off
@@ -0,0 +1,230 @@
+/*
+Copyright 2014 Alexander Okoli
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package goutils
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math"
+	"math/big"
+	"unicode"
+)
+
+/*
+CryptoRandomNonAlphaNumeric creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of all characters (ASCII/Unicode values between 0 to 2,147,483,647 (math.MaxInt32)).
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, CryptoRandom(...)
+*/
+func CryptoRandomNonAlphaNumeric(count int) (string, error) {
+	return CryptoRandomAlphaNumericCustom(count, false, false)
+}
+
+/*
+CryptoRandomAscii creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of characters whose ASCII value is between 32 and 126 (inclusive).
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, CryptoRandom(...)
+*/
+func CryptoRandomAscii(count int) (string, error) {
+	return CryptoRandom(count, 32, 127, false, false)
+}
+
+/*
+CryptoRandomNumeric creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of numeric characters.
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, CryptoRandom(...)
+*/
+func CryptoRandomNumeric(count int) (string, error) {
+	return CryptoRandom(count, 0, 0, false, true)
+}
+
+/*
+CryptoRandomAlphabetic creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
+
+Parameters:
+	count - the length of random string to create
+	letters - if true, generated string may include alphabetic characters
+	numbers - if true, generated string may include numeric characters
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, CryptoRandom(...)
+*/
+func CryptoRandomAlphabetic(count int) (string, error) {
+	return CryptoRandom(count, 0, 0, true, false)
+}
+
+/*
+CryptoRandomAlphaNumeric creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of alpha-numeric characters.
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, CryptoRandom(...)
+*/
+func CryptoRandomAlphaNumeric(count int) (string, error) {
+	return CryptoRandom(count, 0, 0, true, true)
+}
+
+/*
+CryptoRandomAlphaNumericCustom creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
+
+Parameters:
+	count - the length of random string to create
+	letters - if true, generated string may include alphabetic characters
+	numbers - if true, generated string may include numeric characters
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, CryptoRandom(...)
+*/
+func CryptoRandomAlphaNumericCustom(count int, letters bool, numbers bool) (string, error) {
+	return CryptoRandom(count, 0, 0, letters, numbers)
+}
+
+/*
+CryptoRandom creates a random string based on a variety of options, using using golang's crypto/rand source of randomness.
+If the parameters start and end are both 0, start and end are set to ' ' and 'z', the ASCII printable characters, will be used,
+unless letters and numbers are both false, in which case, start and end are set to 0 and math.MaxInt32, respectively.
+If chars is not nil, characters stored in chars that are between start and end are chosen.
+
+Parameters:
+	count - the length of random string to create
+	start - the position in set of chars (ASCII/Unicode int) to start at
+	end - the position in set of chars (ASCII/Unicode int) to end before
+	letters - if true, generated string may include alphabetic characters
+	numbers - if true, generated string may include numeric characters
+	chars - the set of chars to choose randoms from. If nil, then it will use the set of all chars.
+
+Returns:
+	string - the random string
+	error - an error stemming from invalid parameters: if count < 0; or the provided chars array is empty; or end <= start; or end > len(chars)
+*/
+func CryptoRandom(count int, start int, end int, letters bool, numbers bool, chars ...rune) (string, error) {
+	if count == 0 {
+		return "", nil
+	} else if count < 0 {
+		err := fmt.Errorf("randomstringutils illegal argument: Requested random string length %v is less than 0.", count) // equiv to err := errors.New("...")
+		return "", err
+	}
+	if chars != nil && len(chars) == 0 {
+		err := fmt.Errorf("randomstringutils illegal argument: The chars array must not be empty")
+		return "", err
+	}
+
+	if start == 0 && end == 0 {
+		if chars != nil {
+			end = len(chars)
+		} else {
+			if !letters && !numbers {
+				end = math.MaxInt32
+			} else {
+				end = 'z' + 1
+				start = ' '
+			}
+		}
+	} else {
+		if end <= start {
+			err := fmt.Errorf("randomstringutils illegal argument: Parameter end (%v) must be greater than start (%v)", end, start)
+			return "", err
+		}
+
+		if chars != nil && end > len(chars) {
+			err := fmt.Errorf("randomstringutils illegal argument: Parameter end (%v) cannot be greater than len(chars) (%v)", end, len(chars))
+			return "", err
+		}
+	}
+
+	buffer := make([]rune, count)
+	gap := end - start
+
+	// high-surrogates range, (\uD800-\uDBFF) = 55296 - 56319
+	//  low-surrogates range, (\uDC00-\uDFFF) = 56320 - 57343
+
+	for count != 0 {
+		count--
+		var ch rune
+		if chars == nil {
+			ch = rune(getCryptoRandomInt(gap) + int64(start))
+		} else {
+			ch = chars[getCryptoRandomInt(gap)+int64(start)]
+		}
+
+		if letters && unicode.IsLetter(ch) || numbers && unicode.IsDigit(ch) || !letters && !numbers {
+			if ch >= 56320 && ch <= 57343 { // low surrogate range
+				if count == 0 {
+					count++
+				} else {
+					// Insert low surrogate
+					buffer[count] = ch
+					count--
+					// Insert high surrogate
+					buffer[count] = rune(55296 + getCryptoRandomInt(128))
+				}
+			} else if ch >= 55296 && ch <= 56191 { // High surrogates range (Partial)
+				if count == 0 {
+					count++
+				} else {
+					// Insert low surrogate
+					buffer[count] = rune(56320 + getCryptoRandomInt(128))
+					count--
+					// Insert high surrogate
+					buffer[count] = ch
+				}
+			} else if ch >= 56192 && ch <= 56319 {
+				// private high surrogate, skip it
+				count++
+			} else {
+				// not one of the surrogates*
+				buffer[count] = ch
+			}
+		} else {
+			count++
+		}
+	}
+	return string(buffer), nil
+}
+
+func getCryptoRandomInt(count int) int64 {
+	nBig, err := rand.Int(rand.Reader, big.NewInt(int64(count)))
+	if err != nil {
+		panic(err)
+	}
+	return nBig.Int64()
+}
@@ -0,0 +1,248 @@
+/*
+Copyright 2014 Alexander Okoli
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package goutils
+
+import (
+	"fmt"
+	"math"
+	"math/rand"
+	"time"
+	"unicode"
+)
+
+// RANDOM provides the time-based seed used to generate random numbers
+var RANDOM = rand.New(rand.NewSource(time.Now().UnixNano()))
+
+/*
+RandomNonAlphaNumeric creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of all characters (ASCII/Unicode values between 0 to 2,147,483,647 (math.MaxInt32)).
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func RandomNonAlphaNumeric(count int) (string, error) {
+	return RandomAlphaNumericCustom(count, false, false)
+}
+
+/*
+RandomAscii creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of characters whose ASCII value is between 32 and 126 (inclusive).
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func RandomAscii(count int) (string, error) {
+	return Random(count, 32, 127, false, false)
+}
+
+/*
+RandomNumeric creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of numeric characters.
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func RandomNumeric(count int) (string, error) {
+	return Random(count, 0, 0, false, true)
+}
+
+/*
+RandomAlphabetic creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of alphabetic characters.
+
+Parameters:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func RandomAlphabetic(count int) (string, error) {
+	return Random(count, 0, 0, true, false)
+}
+
+/*
+RandomAlphaNumeric creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of alpha-numeric characters.
+
+Parameter:
+	count - the length of random string to create
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func RandomAlphaNumeric(count int) (string, error) {
+	return Random(count, 0, 0, true, true)
+}
+
+/*
+RandomAlphaNumericCustom creates a random string whose length is the number of characters specified.
+Characters will be chosen from the set of alpha-numeric characters as indicated by the arguments.
+
+Parameters:
+	count - the length of random string to create
+	letters - if true, generated string may include alphabetic characters
+	numbers - if true, generated string may include numeric characters
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func RandomAlphaNumericCustom(count int, letters bool, numbers bool) (string, error) {
+	return Random(count, 0, 0, letters, numbers)
+}
+
+/*
+Random creates a random string based on a variety of options, using default source of randomness.
+This method has exactly the same semantics as RandomSeed(int, int, int, bool, bool, []char, *rand.Rand), but
+instead of using an externally supplied source of randomness, it uses the internal *rand.Rand instance.
+
+Parameters:
+	count - the length of random string to create
+	start - the position in set of chars (ASCII/Unicode int) to start at
+	end - the position in set of chars (ASCII/Unicode int) to end before
+	letters - if true, generated string may include alphabetic characters
+	numbers - if true, generated string may include numeric characters
+	chars - the set of chars to choose randoms from. If nil, then it will use the set of all chars.
+
+Returns:
+	string - the random string
+	error - an error stemming from an invalid parameter within underlying function, RandomSeed(...)
+*/
+func Random(count int, start int, end int, letters bool, numbers bool, chars ...rune) (string, error) {
+	return RandomSeed(count, start, end, letters, numbers, chars, RANDOM)
+}
+
+/*
+RandomSeed creates a random string based on a variety of options, using supplied source of randomness.
+If the parameters start and end are both 0, start and end are set to ' ' and 'z', the ASCII printable characters, will be used,
+unless letters and numbers are both false, in which case, start and end are set to 0 and math.MaxInt32, respectively.
+If chars is not nil, characters stored in chars that are between start and end are chosen.
+This method accepts a user-supplied *rand.Rand instance to use as a source of randomness. By seeding a single *rand.Rand instance
+with a fixed seed and using it for each call, the same random sequence of strings can be generated repeatedly and predictably.
+
+Parameters:
+	count - the length of random string to create
+	start - the position in set of chars (ASCII/Unicode decimals) to start at
+	end - the position in set of chars (ASCII/Unicode decimals) to end before
+	letters - if true, generated string may include alphabetic characters
+	numbers - if true, generated string may include numeric characters
+	chars - the set of chars to choose randoms from. If nil, then it will use the set of all chars.
+	random - a source of randomness.
+
+Returns:
+	string - the random string
+	error - an error stemming from invalid parameters: if count < 0; or the provided chars array is empty; or end <= start; or end > len(chars)
+*/
+func RandomSeed(count int, start int, end int, letters bool, numbers bool, chars []rune, random *rand.Rand) (string, error) {
+
+	if count == 0 {
+		return "", nil
+	} else if count < 0 {
+		err := fmt.Errorf("randomstringutils illegal argument: Requested random string length %v is less than 0.", count) // equiv to err := errors.New("...")
+		return "", err
+	}
+	if chars != nil && len(chars) == 0 {
+		err := fmt.Errorf("randomstringutils illegal argument: The chars array must not be empty")
+		return "", err
+	}
+
+	if start == 0 && end == 0 {
+		if chars != nil {
+			end = len(chars)
+		} else {
+			if !letters && !numbers {
+				end = math.MaxInt32
+			} else {
+				end = 'z' + 1
+				start = ' '
+			}
+		}
+	} else {
+		if end <= start {
+			err := fmt.Errorf("randomstringutils illegal argument: Parameter end (%v) must be greater than start (%v)", end, start)
+			return "", err
+		}
+
+		if chars != nil && end > len(chars) {
+			err := fmt.Errorf("randomstringutils illegal argument: Parameter end (%v) cannot be greater than len(chars) (%v)", end, len(chars))
+			return "", err
+		}
+	}
+
+	buffer := make([]rune, count)
+	gap := end - start
+
+	// high-surrogates range, (\uD800-\uDBFF) = 55296 - 56319
+	//  low-surrogates range, (\uDC00-\uDFFF) = 56320 - 57343
+
+	for count != 0 {
+		count--
+		var ch rune
+		if chars == nil {
+			ch = rune(random.Intn(gap) + start)
+		} else {
+			ch = chars[random.Intn(gap)+start]
+		}
+
+		if letters && unicode.IsLetter(ch) || numbers && unicode.IsDigit(ch) || !letters && !numbers {
+			if ch >= 56320 && ch <= 57343 { // low surrogate range
+				if count == 0 {
+					count++
+				} else {
+					// Insert low surrogate
+					buffer[count] = ch
+					count--
+					// Insert high surrogate
+					buffer[count] = rune(55296 + random.Intn(128))
+				}
+			} else if ch >= 55296 && ch <= 56191 { // High surrogates range (Partial)
+				if count == 0 {
+					count++
+				} else {
+					// Insert low surrogate
+					buffer[count] = rune(56320 + random.Intn(128))
+					count--
+					// Insert high surrogate
+					buffer[count] = ch
+				}
+			} else if ch >= 56192 && ch <= 56319 {
+				// private high surrogate, skip it
+				count++
+			} else {
+				// not one of the surrogates*
+				buffer[count] = ch
+			}
+		} else {
+			count++
+		}
+	}
+	return string(buffer), nil
+}
@@ -0,0 +1,240 @@
+/*
+Copyright 2014 Alexander Okoli
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package goutils
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"unicode"
+)
+
+// Typically returned by functions where a searched item cannot be found
+const INDEX_NOT_FOUND = -1
+
+/*
+Abbreviate abbreviates a string using ellipses. This will turn  the string "Now is the time for all good men" into "Now is the time for..."
+
+Specifically, the algorithm is as follows:
+
+    - If str is less than maxWidth characters long, return it.
+    - Else abbreviate it to (str[0:maxWidth - 3] + "...").
+    - If maxWidth is less than 4, return an illegal argument error.
+    - In no case will it return a string of length greater than maxWidth.
+
+Parameters:
+    str -  the string to check
+    maxWidth - maximum length of result string, must be at least 4
+
+Returns:
+    string - abbreviated string
+    error - if the width is too small
+*/
+func Abbreviate(str string, maxWidth int) (string, error) {
+	return AbbreviateFull(str, 0, maxWidth)
+}
+
+/*
+AbbreviateFull abbreviates a string using ellipses. This will turn the string "Now is the time for all good men" into "...is the time for..."
+This function works like Abbreviate(string, int), but allows you to specify a "left edge" offset. Note that this left edge is not
+necessarily going to be the leftmost character in the result, or the first character following the ellipses, but it will appear
+somewhere in the result.
+In no case will it return a string of length greater than maxWidth.
+
+Parameters:
+    str - the string to check
+    offset - left edge of source string
+    maxWidth - maximum length of result string, must be at least 4
+
+Returns:
+    string - abbreviated string
+    error - if the width is too small
+*/
+func AbbreviateFull(str string, offset int, maxWidth int) (string, error) {
+	if str == "" {
+		return "", nil
+	}
+	if maxWidth < 4 {
+		err := fmt.Errorf("stringutils illegal argument: Minimum abbreviation width is 4")
+		return "", err
+	}
+	if len(str) <= maxWidth {
+		return str, nil
+	}
+	if offset > len(str) {
+		offset = len(str)
+	}
+	if len(str)-offset < (maxWidth - 3) { // 15 - 5 < 10 - 3 =  10 < 7
+		offset = len(str) - (maxWidth - 3)
+	}
+	abrevMarker := "..."
+	if offset <= 4 {
+		return str[0:maxWidth-3] + abrevMarker, nil // str.substring(0, maxWidth - 3) + abrevMarker;
+	}
+	if maxWidth < 7 {
+		err := fmt.Errorf("stringutils illegal argument: Minimum abbreviation width with offset is 7")
+		return "", err
+	}
+	if (offset + maxWidth - 3) < len(str) { // 5 + (10-3) < 15 = 12 < 15
+		abrevStr, _ := Abbreviate(str[offset:len(str)], (maxWidth - 3))
+		return abrevMarker + abrevStr, nil // abrevMarker + abbreviate(str.substring(offset), maxWidth - 3);
+	}
+	return abrevMarker + str[(len(str)-(maxWidth-3)):len(str)], nil // abrevMarker + str.substring(str.length() - (maxWidth - 3));
+}
+
+/*
+DeleteWhiteSpace deletes all whitespaces from a string as defined by unicode.IsSpace(rune).
+It returns the string without whitespaces.
+
+Parameter:
+    str - the string to delete whitespace from, may be nil
+
+Returns:
+    the string without whitespaces
+*/
+func DeleteWhiteSpace(str string) string {
+	if str == "" {
+		return str
+	}
+	sz := len(str)
+	var chs bytes.Buffer
+	count := 0
+	for i := 0; i < sz; i++ {
+		ch := rune(str[i])
+		if !unicode.IsSpace(ch) {
+			chs.WriteRune(ch)
+			count++
+		}
+	}
+	if count == sz {
+		return str
+	}
+	return chs.String()
+}
+
+/*
+IndexOfDifference compares two strings, and returns the index at which the strings begin to differ.
+
+Parameters:
+    str1 - the first string
+    str2 - the second string
+
+Returns:
+    the index where str1 and str2 begin to differ; -1 if they are equal
+*/
+func IndexOfDifference(str1 string, str2 string) int {
+	if str1 == str2 {
+		return INDEX_NOT_FOUND
+	}
+	if IsEmpty(str1) || IsEmpty(str2) {
+		return 0
+	}
+	var i int
+	for i = 0; i < len(str1) && i < len(str2); i++ {
+		if rune(str1[i]) != rune(str2[i]) {
+			break
+		}
+	}
+	if i < len(str2) || i < len(str1) {
+		return i
+	}
+	return INDEX_NOT_FOUND
+}
+
+/*
+IsBlank checks if a string is whitespace or empty (""). Observe the following behavior:
+
+    goutils.IsBlank("")        = true
+    goutils.IsBlank(" ")       = true
+    goutils.IsBlank("bob")     = false
+    goutils.IsBlank("  bob  ") = false
+
+Parameter:
+    str - the string to check
+
+Returns:
+    true - if the string is whitespace or empty ("")
+*/
+func IsBlank(str string) bool {
+	strLen := len(str)
+	if str == "" || strLen == 0 {
+		return true
+	}
+	for i := 0; i < strLen; i++ {
+		if unicode.IsSpace(rune(str[i])) == false {
+			return false
+		}
+	}
+	return true
+}
+
+/*
+IndexOf returns the index of the first instance of sub in str, with the search beginning from the
+index start point specified. -1 is returned if sub is not present in str.
+
+An empty string ("") will return -1 (INDEX_NOT_FOUND). A negative start position is treated as zero.
+A start position greater than the string length returns -1.
+
+Parameters:
+    str - the string to check
+    sub - the substring to find
+    start - the start position; negative treated as zero
+
+Returns:
+    the first index where the sub string was found  (always >= start)
+*/
+func IndexOf(str string, sub string, start int) int {
+
+	if start < 0 {
+		start = 0
+	}
+
+	if len(str) < start {
+		return INDEX_NOT_FOUND
+	}
+
+	if IsEmpty(str) || IsEmpty(sub) {
+		return INDEX_NOT_FOUND
+	}
+
+	partialIndex := strings.Index(str[start:len(str)], sub)
+	if partialIndex == -1 {
+		return INDEX_NOT_FOUND
+	}
+	return partialIndex + start
+}
+
+// IsEmpty checks if a string is empty (""). Returns true if empty, and false otherwise.
+func IsEmpty(str string) bool {
+	return len(str) == 0
+}
+
+// Returns either the passed in string, or if the string is empty, the value of defaultStr.
+func DefaultString(str string, defaultStr string) string {
+	if IsEmpty(str) {
+		return defaultStr
+	}
+	return str
+}
+
+// Returns either the passed in string, or if the string is whitespace, empty (""), the value of defaultStr.
+func DefaultIfBlank(str string, defaultStr string) string {
+	if IsBlank(str) {
+		return defaultStr
+	}
+	return str
+}
@@ -0,0 +1,357 @@
+/*
+Copyright 2014 Alexander Okoli
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/*
+Package goutils provides utility functions to manipulate strings in various ways.
+The code snippets below show examples of how to use goutils. Some functions return
+errors while others do not, so usage would vary as a result.
+
+Example:
+
+    package main
+
+    import (
+        "fmt"
+        "github.com/aokoli/goutils"
+    )
+
+    func main() {
+
+        // EXAMPLE 1: A goutils function which returns no errors
+        fmt.Println (goutils.Initials("John Doe Foo")) // Prints out "JDF"
+
+
+
+        // EXAMPLE 2: A goutils function which returns an error
+        rand1, err1 := goutils.Random (-1, 0, 0, true, true)
+
+        if err1 != nil {
+            fmt.Println(err1) // Prints out error message because -1 was entered as the first parameter in goutils.Random(...)
+        } else {
+            fmt.Println(rand1)
+        }
+    }
+*/
+package goutils
+
+import (
+	"bytes"
+	"strings"
+	"unicode"
+)
+
+// VERSION indicates the current version of goutils
+const VERSION = "1.0.0"
+
+/*
+Wrap wraps a single line of text, identifying words by ' '.
+New lines will be separated by '\n'. Very long words, such as URLs will not be wrapped.
+Leading spaces on a new line are stripped. Trailing spaces are not stripped.
+
+Parameters:
+    str - the string to be word wrapped
+    wrapLength - the column (a column can fit only one character) to wrap the words at, less than 1 is treated as 1
+
+Returns:
+    a line with newlines inserted
+*/
+func Wrap(str string, wrapLength int) string {
+	return WrapCustom(str, wrapLength, "", false)
+}
+
+/*
+WrapCustom wraps a single line of text, identifying words by ' '.
+Leading spaces on a new line are stripped. Trailing spaces are not stripped.
+
+Parameters:
+    str - the string to be word wrapped
+    wrapLength - the column number (a column can fit only one character) to wrap the words at, less than 1 is treated as 1
+    newLineStr - the string to insert for a new line, "" uses '\n'
+    wrapLongWords - true if long words (such as URLs) should be wrapped
+
+Returns:
+    a line with newlines inserted
+*/
+func WrapCustom(str string, wrapLength int, newLineStr string, wrapLongWords bool) string {
+
+	if str == "" {
+		return ""
+	}
+	if newLineStr == "" {
+		newLineStr = "\n" // TODO Assumes "\n" is seperator. Explore SystemUtils.LINE_SEPARATOR from Apache Commons
+	}
+	if wrapLength < 1 {
+		wrapLength = 1
+	}
+
+	inputLineLength := len(str)
+	offset := 0
+
+	var wrappedLine bytes.Buffer
+
+	for inputLineLength-offset > wrapLength {
+
+		if rune(str[offset]) == ' ' {
+			offset++
+			continue
+		}
+
+		end := wrapLength + offset + 1
+		spaceToWrapAt := strings.LastIndex(str[offset:end], " ") + offset
+
+		if spaceToWrapAt >= offset {
+			// normal word (not longer than wrapLength)
+			wrappedLine.WriteString(str[offset:spaceToWrapAt])
+			wrappedLine.WriteString(newLineStr)
+			offset = spaceToWrapAt + 1
+
+		} else {
+			// long word or URL
+			if wrapLongWords {
+				end := wrapLength + offset
+				// long words are wrapped one line at a time
+				wrappedLine.WriteString(str[offset:end])
+				wrappedLine.WriteString(newLineStr)
+				offset += wrapLength
+			} else {
+				// long words aren't wrapped, just extended beyond limit
+				end := wrapLength + offset
+				index := strings.IndexRune(str[end:len(str)], ' ')
+				if index == -1 {
+					wrappedLine.WriteString(str[offset:len(str)])
+					offset = inputLineLength
+				} else {
+					spaceToWrapAt = index + end
+					wrappedLine.WriteString(str[offset:spaceToWrapAt])
+					wrappedLine.WriteString(newLineStr)
+					offset = spaceToWrapAt + 1
+				}
+			}
+		}
+	}
+
+	wrappedLine.WriteString(str[offset:len(str)])
+
+	return wrappedLine.String()
+
+}
+
+/*
+Capitalize capitalizes all the delimiter separated words in a string. Only the first letter of each word is changed.
+To convert the rest of each word to lowercase at the same time, use CapitalizeFully(str string, delimiters ...rune).
+The delimiters represent a set of characters understood to separate words. The first string character
+and the first non-delimiter character after a delimiter will be capitalized. A "" input string returns "".
+Capitalization uses the Unicode title case, normally equivalent to upper case.
+
+Parameters:
+    str - the string to capitalize
+    delimiters - set of characters to determine capitalization, exclusion of this parameter means whitespace would be delimeter
+
+Returns:
+    capitalized string
+*/
+func Capitalize(str string, delimiters ...rune) string {
+
+	var delimLen int
+
+	if delimiters == nil {
+		delimLen = -1
+	} else {
+		delimLen = len(delimiters)
+	}
+
+	if str == "" || delimLen == 0 {
+		return str
+	}
+
+	buffer := []rune(str)
+	capitalizeNext := true
+	for i := 0; i < len(buffer); i++ {
+		ch := buffer[i]
+		if isDelimiter(ch, delimiters...) {
+			capitalizeNext = true
+		} else if capitalizeNext {
+			buffer[i] = unicode.ToTitle(ch)
+			capitalizeNext = false
+		}
+	}
+	return string(buffer)
+
+}
+
+/*
+CapitalizeFully converts all the delimiter separated words in a string into capitalized words, that is each word is made up of a
+titlecase character and then a series of lowercase characters. The delimiters represent a set of characters understood
+to separate words. The first string character and the first non-delimiter character after a delimiter will be capitalized.
+Capitalization uses the Unicode title case, normally equivalent to upper case.
+
+Parameters:
+    str - the string to capitalize fully
+    delimiters - set of characters to determine capitalization, exclusion of this parameter means whitespace would be delimeter
+
+Returns:
+    capitalized string
+*/
+func CapitalizeFully(str string, delimiters ...rune) string {
+
+	var delimLen int
+
+	if delimiters == nil {
+		delimLen = -1
+	} else {
+		delimLen = len(delimiters)
+	}
+
+	if str == "" || delimLen == 0 {
+		return str
+	}
+	str = strings.ToLower(str)
+	return Capitalize(str, delimiters...)
+}
+
+/*
+Uncapitalize uncapitalizes all the whitespace separated words in a string. Only the first letter of each word is changed.
+The delimiters represent a set of characters understood to separate words. The first string character and the first non-delimiter
+character after a delimiter will be uncapitalized. Whitespace is defined by unicode.IsSpace(char).
+
+Parameters:
+    str - the string to uncapitalize fully
+    delimiters - set of characters to determine capitalization, exclusion of this parameter means whitespace would be delimeter
+
+Returns:
+    uncapitalized string
+*/
+func Uncapitalize(str string, delimiters ...rune) string {
+
+	var delimLen int
+
+	if delimiters == nil {
+		delimLen = -1
+	} else {
+		delimLen = len(delimiters)
+	}
+
+	if str == "" || delimLen == 0 {
+		return str
+	}
+
+	buffer := []rune(str)
+	uncapitalizeNext := true // TODO Always makes capitalize/un apply to first char.
+	for i := 0; i < len(buffer); i++ {
+		ch := buffer[i]
+		if isDelimiter(ch, delimiters...) {
+			uncapitalizeNext = true
+		} else if uncapitalizeNext {
+			buffer[i] = unicode.ToLower(ch)
+			uncapitalizeNext = false
+		}
+	}
+	return string(buffer)
+}
+
+/*
+SwapCase swaps the case of a string using a word based algorithm.
+
+Conversion algorithm:
+
+    Upper case character converts to Lower case
+    Title case character converts to Lower case
+    Lower case character after Whitespace or at start converts to Title case
+    Other Lower case character converts to Upper case
+    Whitespace is defined by unicode.IsSpace(char).
+
+Parameters:
+    str - the string to swap case
+
+Returns:
+    the changed string
+*/
+func SwapCase(str string) string {
+	if str == "" {
+		return str
+	}
+	buffer := []rune(str)
+
+	whitespace := true
+
+	for i := 0; i < len(buffer); i++ {
+		ch := buffer[i]
+		if unicode.IsUpper(ch) {
+			buffer[i] = unicode.ToLower(ch)
+			whitespace = false
+		} else if unicode.IsTitle(ch) {
+			buffer[i] = unicode.ToLower(ch)
+			whitespace = false
+		} else if unicode.IsLower(ch) {
+			if whitespace {
+				buffer[i] = unicode.ToTitle(ch)
+				whitespace = false
+			} else {
+				buffer[i] = unicode.ToUpper(ch)
+			}
+		} else {
+			whitespace = unicode.IsSpace(ch)
+		}
+	}
+	return string(buffer)
+}
+
+/*
+Initials extracts the initial letters from each word in the string. The first letter of the string and all first
+letters after the defined delimiters are returned as a new string. Their case is not changed. If the delimiters
+parameter is excluded, then Whitespace is used. Whitespace is defined by unicode.IsSpacea(char). An empty delimiter array returns an empty string.
+
+Parameters:
+    str - the string to get initials from
+    delimiters - set of characters to determine words, exclusion of this parameter means whitespace would be delimeter
+Returns:
+    string of initial letters
+*/
+func Initials(str string, delimiters ...rune) string {
+	if str == "" {
+		return str
+	}
+	if delimiters != nil && len(delimiters) == 0 {
+		return ""
+	}
+	strLen := len(str)
+	var buf bytes.Buffer
+	lastWasGap := true
+	for i := 0; i < strLen; i++ {
+		ch := rune(str[i])
+
+		if isDelimiter(ch, delimiters...) {
+			lastWasGap = true
+		} else if lastWasGap {
+			buf.WriteRune(ch)
+			lastWasGap = false
+		}
+	}
+	return buf.String()
+}
+
+// private function (lower case func name)
+func isDelimiter(ch rune, delimiters ...rune) bool {
+	if delimiters == nil {
+		return unicode.IsSpace(ch)
+	}
+	for _, delimiter := range delimiters {
+		if ch == delimiter {
+			return true
+		}
+	}
+	return false
+}
@@ -0,0 +1,29 @@
+language: go
+
+go:
+  - 1.6.x
+  - 1.7.x
+  - 1.8.x
+  - 1.9.x
+  - 1.10.x
+  - 1.11.x
+  - 1.12.x
+  - tip
+
+# Setting sudo access to false will let Travis CI use containers rather than
+# VMs to run the tests. For more details see:
+# - http://docs.travis-ci.com/user/workers/container-based-infrastructure/
+# - http://docs.travis-ci.com/user/workers/standard-infrastructure/
+sudo: false
+
+script:
+  - make setup
+  - make test
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/06e3328629952dabe3e0
+    on_success: change  # options: [always|never|change] default: always
+    on_failure: always  # options: [always|never|change] default: always
+    on_start: never     # options: [always|never|change] default: always
@@ -0,0 +1,109 @@
+# 1.5.0 (2019-09-11)
+
+## Added
+
+- #103: Add basic fuzzing for `NewVersion()` (thanks @jesse-c)
+
+## Changed
+
+- #82: Clarify wildcard meaning in range constraints and update tests for it (thanks @greysteil)
+- #83: Clarify caret operator range for pre-1.0.0 dependencies (thanks @greysteil)
+- #72: Adding docs comment pointing to vert for a cli
+- #71: Update the docs on pre-release comparator handling
+- #89: Test with new go versions (thanks @thedevsaddam)
+- #87: Added $ to ValidPrerelease for better validation (thanks @jeremycarroll)
+
+## Fixed
+
+- #78: Fix unchecked error in example code (thanks @ravron)
+- #70: Fix the handling of pre-releases and the 0.0.0 release edge case
+- #97: Fixed copyright file for proper display on GitHub
+- #107: Fix handling prerelease when sorting alphanum and num 
+- #109: Fixed where Validate sometimes returns wrong message on error
+
+# 1.4.2 (2018-04-10)
+
+## Changed
+- #72: Updated the docs to point to vert for a console appliaction
+- #71: Update the docs on pre-release comparator handling
+
+## Fixed
+- #70: Fix the handling of pre-releases and the 0.0.0 release edge case
+
+# 1.4.1 (2018-04-02)
+
+## Fixed
+- Fixed #64: Fix pre-release precedence issue (thanks @uudashr)
+
+# 1.4.0 (2017-10-04)
+
+## Changed
+- #61: Update NewVersion to parse ints with a 64bit int size (thanks @zknill)
+
+# 1.3.1 (2017-07-10)
+
+## Fixed
+- Fixed #57: number comparisons in prerelease sometimes inaccurate
+
+# 1.3.0 (2017-05-02)
+
+## Added
+- #45: Added json (un)marshaling support (thanks @mh-cbon)
+- Stability marker. See https://masterminds.github.io/stability/
+
+## Fixed
+- #51: Fix handling of single digit tilde constraint (thanks @dgodd)
+
+## Changed
+- #55: The godoc icon moved from png to svg
+
+# 1.2.3 (2017-04-03)
+
+## Fixed
+- #46: Fixed 0.x.x and 0.0.x in constraints being treated as *
+
+# Release 1.2.2 (2016-12-13)
+
+## Fixed
+- #34: Fixed issue where hyphen range was not working with pre-release parsing.
+
+# Release 1.2.1 (2016-11-28)
+
+## Fixed
+- #24: Fixed edge case issue where constraint "> 0" does not handle "0.0.1-alpha"
+  properly.
+
+# Release 1.2.0 (2016-11-04)
+
+## Added
+- #20: Added MustParse function for versions (thanks @adamreese)
+- #15: Added increment methods on versions (thanks @mh-cbon)
+
+## Fixed
+- Issue #21: Per the SemVer spec (section 9) a pre-release is unstable and
+  might not satisfy the intended compatibility. The change here ignores pre-releases
+  on constraint checks (e.g., ~ or ^) when a pre-release is not part of the
+  constraint. For example, `^1.2.3` will ignore pre-releases while
+  `^1.2.3-alpha` will include them.
+
+# Release 1.1.1 (2016-06-30)
+
+## Changed
+- Issue #9: Speed up version comparison performance (thanks @sdboyer)
+- Issue #8: Added benchmarks (thanks @sdboyer)
+- Updated Go Report Card URL to new location
+- Updated Readme to add code snippet formatting (thanks @mh-cbon)
+- Updating tagging to v[SemVer] structure for compatibility with other tools.
+
+# Release 1.1.0 (2016-03-11)
+
+- Issue #2: Implemented validation to provide reasons a versions failed a
+  constraint.
+
+# Release 1.0.1 (2015-12-31)
+
+- Fixed #1: * constraint failing on valid versions.
+
+# Release 1.0.0 (2015-10-20)
+
+- Initial release
--- a/Show More
+++ b/Show More