Initial QSfera import

Server/vendor/github.com/moby/sys/sequential/sequential_windows.go

@@ -0,0 +1,162 @@
+package sequential
+
+import (
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// Create is a copy of [os.Create], modified to use sequential file access.
+//
+// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
+// as implemented in golang. Refer to the [Win32 API documentation] for details
+// on sequential file access.
+//
+// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
+func Create(name string) (*os.File, error) {
+	return openFileSequential(name, windows.O_RDWR|windows.O_CREAT|windows.O_TRUNC)
+}
+
+// Open is a copy of [os.Open], modified to use sequential file access.
+//
+// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
+// as implemented in golang. Refer to the [Win32 API documentation] for details
+// on sequential file access.
+//
+// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
+func Open(name string) (*os.File, error) {
+	return openFileSequential(name, windows.O_RDONLY)
+}
+
+// OpenFile is a copy of [os.OpenFile], modified to use sequential file access.
+//
+// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
+// as implemented in golang. Refer to the [Win32 API documentation] for details
+// on sequential file access.
+//
+// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
+func OpenFile(name string, flag int, _ os.FileMode) (*os.File, error) {
+	return openFileSequential(name, flag)
+}
+
+func openFileSequential(name string, flag int) (file *os.File, err error) {
+	if name == "" {
+		return nil, &os.PathError{Op: "open", Path: name, Err: windows.ERROR_FILE_NOT_FOUND}
+	}
+	r, e := openSequential(name, flag|windows.O_CLOEXEC)
+	if e != nil {
+		return nil, &os.PathError{Op: "open", Path: name, Err: e}
+	}
+	return os.NewFile(uintptr(r), name), nil
+}
+
+func makeInheritSa() *windows.SecurityAttributes {
+	var sa windows.SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	return &sa
+}
+
+func openSequential(path string, mode int) (fd windows.Handle, err error) {
+	if len(path) == 0 {
+		return windows.InvalidHandle, windows.ERROR_FILE_NOT_FOUND
+	}
+	pathp, err := windows.UTF16PtrFromString(path)
+	if err != nil {
+		return windows.InvalidHandle, err
+	}
+	var access uint32
+	switch mode & (windows.O_RDONLY | windows.O_WRONLY | windows.O_RDWR) {
+	case windows.O_RDONLY:
+		access = windows.GENERIC_READ
+	case windows.O_WRONLY:
+		access = windows.GENERIC_WRITE
+	case windows.O_RDWR:
+		access = windows.GENERIC_READ | windows.GENERIC_WRITE
+	}
+	if mode&windows.O_CREAT != 0 {
+		access |= windows.GENERIC_WRITE
+	}
+	if mode&windows.O_APPEND != 0 {
+		access &^= windows.GENERIC_WRITE
+		access |= windows.FILE_APPEND_DATA
+	}
+	sharemode := uint32(windows.FILE_SHARE_READ | windows.FILE_SHARE_WRITE)
+	var sa *windows.SecurityAttributes
+	if mode&windows.O_CLOEXEC == 0 {
+		sa = makeInheritSa()
+	}
+	var createmode uint32
+	switch {
+	case mode&(windows.O_CREAT|windows.O_EXCL) == (windows.O_CREAT | windows.O_EXCL):
+		createmode = windows.CREATE_NEW
+	case mode&(windows.O_CREAT|windows.O_TRUNC) == (windows.O_CREAT | windows.O_TRUNC):
+		createmode = windows.CREATE_ALWAYS
+	case mode&windows.O_CREAT == windows.O_CREAT:
+		createmode = windows.OPEN_ALWAYS
+	case mode&windows.O_TRUNC == windows.O_TRUNC:
+		createmode = windows.TRUNCATE_EXISTING
+	default:
+		createmode = windows.OPEN_EXISTING
+	}
+	// Use FILE_FLAG_SEQUENTIAL_SCAN rather than FILE_ATTRIBUTE_NORMAL as implemented in golang.
+	// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
+	h, e := windows.CreateFile(pathp, access, sharemode, sa, createmode, windows.FILE_FLAG_SEQUENTIAL_SCAN, 0)
+	return h, e
+}
+
+// Helpers for CreateTemp
+var (
+	rand   uint32
+	randmu sync.Mutex
+)
+
+func reseed() uint32 {
+	return uint32(time.Now().UnixNano() + int64(os.Getpid()))
+}
+
+func nextSuffix() string {
+	randmu.Lock()
+	r := rand
+	if r == 0 {
+		r = reseed()
+	}
+	r = r*1664525 + 1013904223 // constants from Numerical Recipes
+	rand = r
+	randmu.Unlock()
+	return strconv.Itoa(int(1e9 + r%1e9))[1:]
+}
+
+// CreateTemp is a copy of [os.CreateTemp], modified to use sequential file access.
+//
+// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
+// as implemented in golang. Refer to the [Win32 API documentation] for details
+// on sequential file access.
+//
+// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
+func CreateTemp(dir, prefix string) (f *os.File, err error) {
+	if dir == "" {
+		dir = os.TempDir()
+	}
+
+	nconflict := 0
+	for i := 0; i < 10000; i++ {
+		name := filepath.Join(dir, prefix+nextSuffix())
+		f, err = openFileSequential(name, windows.O_RDWR|windows.O_CREAT|windows.O_EXCL)
+		if os.IsExist(err) {
+			if nconflict++; nconflict > 10 {
+				randmu.Lock()
+				rand = reseed()
+				randmu.Unlock()
+			}
+			continue
+		}
+		break
+	}
+	return
+}