Initial QSfera import
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Курнат Андрей
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// Copyright 2023 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package parse
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import (
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"fmt"
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"strings"
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"unicode"
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"unicode/utf8"
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)
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const (
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eof rune = -1
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)
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func isReserved(r rune) bool {
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return unicode.IsSpace(r) || strings.ContainsRune("{}!=~,\\\"'`", r)
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}
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// expectedError is returned when the next rune does not match what is expected.
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type expectedError struct {
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position
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input string
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expected string
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}
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func (e expectedError) Error() string {
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if e.offsetEnd >= len(e.input) {
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return fmt.Sprintf("%d:%d: unexpected end of input, expected one of '%s'",
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e.columnStart,
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e.columnEnd,
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e.expected,
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)
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}
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return fmt.Sprintf("%d:%d: %s: expected one of '%s'",
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e.columnStart,
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e.columnEnd,
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e.input[e.offsetStart:e.offsetEnd],
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e.expected,
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)
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}
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// invalidInputError is returned when the next rune in the input does not match
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// the grammar of Prometheus-like matchers.
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type invalidInputError struct {
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position
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input string
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}
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func (e invalidInputError) Error() string {
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return fmt.Sprintf("%d:%d: %s: invalid input",
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e.columnStart,
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e.columnEnd,
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e.input[e.offsetStart:e.offsetEnd],
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)
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}
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// unterminatedError is returned when text in quotes does not have a closing quote.
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type unterminatedError struct {
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position
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input string
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quote rune
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}
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func (e unterminatedError) Error() string {
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return fmt.Sprintf("%d:%d: %s: missing end %c",
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e.columnStart,
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e.columnEnd,
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e.input[e.offsetStart:e.offsetEnd],
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e.quote,
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)
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}
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// lexer scans a sequence of tokens that match the grammar of Prometheus-like
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// matchers. A token is emitted for each call to scan() which returns the
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// next token in the input or an error if the input does not conform to the
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// grammar. A token can be one of a number of kinds and corresponds to a
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// subslice of the input. Once the input has been consumed successive calls to
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// scan() return a tokenEOF token.
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type lexer struct {
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input string
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err error
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start int // The offset of the current token.
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pos int // The position of the cursor in the input.
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width int // The width of the last rune.
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column int // The column offset of the current token.
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cols int // The number of columns (runes) decoded from the input.
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}
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// Scans the next token in the input or an error if the input does not
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// conform to the grammar. Once the input has been consumed successive
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// calls scan() return a tokenEOF token.
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func (l *lexer) scan() (token, error) {
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t := token{}
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// Do not attempt to emit more tokens if the input is invalid.
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if l.err != nil {
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return t, l.err
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}
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// Iterate over each rune in the input and either emit a token or an error.
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for r := l.next(); r != eof; r = l.next() {
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switch {
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case r == '{':
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t = l.emit(tokenOpenBrace)
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return t, l.err
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case r == '}':
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t = l.emit(tokenCloseBrace)
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return t, l.err
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case r == ',':
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t = l.emit(tokenComma)
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return t, l.err
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case r == '=' || r == '!':
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l.rewind()
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t, l.err = l.scanOperator()
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return t, l.err
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case r == '"':
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l.rewind()
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t, l.err = l.scanQuoted()
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return t, l.err
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case !isReserved(r):
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l.rewind()
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t, l.err = l.scanUnquoted()
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return t, l.err
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case unicode.IsSpace(r):
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l.skip()
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default:
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l.err = invalidInputError{
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position: l.position(),
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input: l.input,
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}
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return t, l.err
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}
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}
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return t, l.err
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}
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func (l *lexer) scanOperator() (token, error) {
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// If the first rune is an '!' then it must be followed with either an
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// '=' or '~' to not match a string or regex.
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if l.accept("!") {
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if l.accept("=") {
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return l.emit(tokenNotEquals), nil
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}
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if l.accept("~") {
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return l.emit(tokenNotMatches), nil
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}
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return token{}, expectedError{
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position: l.position(),
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input: l.input,
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expected: "=~",
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}
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}
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// If the first rune is an '=' then it can be followed with an optional
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// '~' to match a regex.
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if l.accept("=") {
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if l.accept("~") {
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return l.emit(tokenMatches), nil
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}
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return l.emit(tokenEquals), nil
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}
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return token{}, expectedError{
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position: l.position(),
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input: l.input,
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expected: "!=",
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}
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}
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func (l *lexer) scanQuoted() (token, error) {
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if err := l.expect("\""); err != nil {
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return token{}, err
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}
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var isEscaped bool
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for r := l.next(); r != eof; r = l.next() {
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if isEscaped {
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isEscaped = false
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} else if r == '\\' {
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isEscaped = true
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} else if r == '"' {
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l.rewind()
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break
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}
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}
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if err := l.expect("\""); err != nil {
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return token{}, unterminatedError{
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position: l.position(),
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input: l.input,
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quote: '"',
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}
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}
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return l.emit(tokenQuoted), nil
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}
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func (l *lexer) scanUnquoted() (token, error) {
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for r := l.next(); r != eof; r = l.next() {
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if isReserved(r) {
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l.rewind()
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break
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}
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}
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return l.emit(tokenUnquoted), nil
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}
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// peek the next token in the input or an error if the input does not
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// conform to the grammar. Once the input has been consumed successive
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// calls peek() return a tokenEOF token.
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func (l *lexer) peek() (token, error) {
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start := l.start
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pos := l.pos
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width := l.width
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column := l.column
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cols := l.cols
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// Do not reset l.err because we can return it on the next call to scan().
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defer func() {
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l.start = start
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l.pos = pos
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l.width = width
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l.column = column
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l.cols = cols
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}()
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return l.scan()
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}
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// position returns the position of the last emitted token.
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func (l *lexer) position() position {
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return position{
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offsetStart: l.start,
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offsetEnd: l.pos,
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columnStart: l.column,
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columnEnd: l.cols,
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}
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}
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// accept consumes the next if its one of the valid runes.
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// It returns true if the next rune was accepted, otherwise false.
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func (l *lexer) accept(valid string) bool {
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if strings.ContainsRune(valid, l.next()) {
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return true
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}
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l.rewind()
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return false
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}
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// expect consumes the next rune if its one of the valid runes.
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// It returns nil if the next rune is valid, otherwise an expectedError
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// error.
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func (l *lexer) expect(valid string) error {
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if strings.ContainsRune(valid, l.next()) {
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return nil
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}
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l.rewind()
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return expectedError{
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position: l.position(),
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input: l.input,
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expected: valid,
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}
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}
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// emits returns the scanned input as a token.
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func (l *lexer) emit(kind tokenKind) token {
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t := token{
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kind: kind,
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value: l.input[l.start:l.pos],
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position: l.position(),
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}
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l.start = l.pos
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l.column = l.cols
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return t
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}
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// next returns the next rune in the input or eof.
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func (l *lexer) next() rune {
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if l.pos >= len(l.input) {
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l.width = 0
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return eof
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}
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r, width := utf8.DecodeRuneInString(l.input[l.pos:])
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l.width = width
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l.pos += width
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l.cols++
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return r
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}
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// rewind the last rune in the input. It should not be called more than once
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// between consecutive calls of next.
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func (l *lexer) rewind() {
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l.pos -= l.width
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// When the next rune in the input is eof the width is zero. This check
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// prevents cols from being decremented when the next rune being accepted
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// is instead eof.
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if l.width > 0 {
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l.cols--
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}
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}
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// skip the scanned input between start and pos.
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func (l *lexer) skip() {
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l.start = l.pos
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l.column = l.cols
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}
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