src/os/types_windows.go - go - Git at Google

 // 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 os

 import (
 	"internal/filepathlite"
 	"internal/godebug"
 	"internal/syscall/windows"
 	"sync"
 	"syscall"
 	"time"
 	"unsafe"
 )

 // A fileStat is the implementation of FileInfo returned by Stat and Lstat.
 type fileStat struct {
 	name string

 	// from ByHandleFileInformation, Win32FileAttributeData, Win32finddata, and GetFileInformationByHandleEx
 	FileAttributes uint32
 	CreationTime   syscall.Filetime
 	LastAccessTime syscall.Filetime
 	LastWriteTime  syscall.Filetime
 	FileSizeHigh   uint32
 	FileSizeLow    uint32

 	// from Win32finddata and GetFileInformationByHandleEx
 	ReparseTag uint32

 	// what syscall.GetFileType returns
 	filetype uint32

 	// used to implement SameFile
 	sync.Mutex
 	path             string
 	vol              uint32
 	idxhi            uint32
 	idxlo            uint32
 	appendNameToPath bool
 }

 // newFileStatFromGetFileInformationByHandle calls GetFileInformationByHandle
 // to gather all required information about the file handle h.
 func newFileStatFromGetFileInformationByHandle(path string, h syscall.Handle) (fs *fileStat, err error) {
 	var d syscall.ByHandleFileInformation
 	err = syscall.GetFileInformationByHandle(h, &d)
 	if err != nil {
 		return nil, &PathError{Op: "GetFileInformationByHandle", Path: path, Err: err}
 	}

 	var reparseTag uint32
 	if d.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
 		var ti windows.FILE_ATTRIBUTE_TAG_INFO
 		err = windows.GetFileInformationByHandleEx(h, windows.FileAttributeTagInfo, (*byte)(unsafe.Pointer(&ti)), uint32(unsafe.Sizeof(ti)))
 		if err != nil {
 			return nil, &PathError{Op: "GetFileInformationByHandleEx", Path: path, Err: err}
 		}
 		reparseTag = ti.ReparseTag
 	}

 	return &fileStat{
 		name:           filepathlite.Base(path),
 		FileAttributes: d.FileAttributes,
 		CreationTime:   d.CreationTime,
 		LastAccessTime: d.LastAccessTime,
 		LastWriteTime:  d.LastWriteTime,
 		FileSizeHigh:   d.FileSizeHigh,
 		FileSizeLow:    d.FileSizeLow,
 		vol:            d.VolumeSerialNumber,
 		idxhi:          d.FileIndexHigh,
 		idxlo:          d.FileIndexLow,
 		ReparseTag:     reparseTag,
 		// fileStat.path is used by os.SameFile to decide if it needs
 		// to fetch vol, idxhi and idxlo. But these are already set,
 		// so set fileStat.path to "" to prevent os.SameFile doing it again.
 	}, nil
 }

 // newFileStatFromWin32FileAttributeData copies all required information
 // from syscall.Win32FileAttributeData d into the newly created fileStat.
 func newFileStatFromWin32FileAttributeData(d *syscall.Win32FileAttributeData) *fileStat {
 	return &fileStat{
 		FileAttributes: d.FileAttributes,
 		CreationTime:   d.CreationTime,
 		LastAccessTime: d.LastAccessTime,
 		LastWriteTime:  d.LastWriteTime,
 		FileSizeHigh:   d.FileSizeHigh,
 		FileSizeLow:    d.FileSizeLow,
 	}
 }

 // newFileStatFromFileIDBothDirInfo copies all required information
 // from windows.FILE_ID_BOTH_DIR_INFO d into the newly created fileStat.
 func newFileStatFromFileIDBothDirInfo(d *windows.FILE_ID_BOTH_DIR_INFO) *fileStat {
 	// The FILE_ID_BOTH_DIR_INFO MSDN documentations isn't completely correct.
 	// FileAttributes can contain any file attributes that is currently set on the file,
 	// not just the ones documented.
 	// EaSize contains the reparse tag if the file is a reparse point.
 	return &fileStat{
 		FileAttributes: d.FileAttributes,
 		CreationTime:   d.CreationTime,
 		LastAccessTime: d.LastAccessTime,
 		LastWriteTime:  d.LastWriteTime,
 		FileSizeHigh:   uint32(d.EndOfFile >> 32),
 		FileSizeLow:    uint32(d.EndOfFile),
 		ReparseTag:     d.EaSize,
 		idxhi:          uint32(d.FileID >> 32),
 		idxlo:          uint32(d.FileID),
 	}
 }

 // newFileStatFromFileFullDirInfo copies all required information
 // from windows.FILE_FULL_DIR_INFO d into the newly created fileStat.
 func newFileStatFromFileFullDirInfo(d *windows.FILE_FULL_DIR_INFO) *fileStat {
 	return &fileStat{
 		FileAttributes: d.FileAttributes,
 		CreationTime:   d.CreationTime,
 		LastAccessTime: d.LastAccessTime,
 		LastWriteTime:  d.LastWriteTime,
 		FileSizeHigh:   uint32(d.EndOfFile >> 32),
 		FileSizeLow:    uint32(d.EndOfFile),
 		ReparseTag:     d.EaSize,
 	}
 }

 // newFileStatFromWin32finddata copies all required information
 // from syscall.Win32finddata d into the newly created fileStat.
 func newFileStatFromWin32finddata(d *syscall.Win32finddata) *fileStat {
 	fs := &fileStat{
 		FileAttributes: d.FileAttributes,
 		CreationTime:   d.CreationTime,
 		LastAccessTime: d.LastAccessTime,
 		LastWriteTime:  d.LastWriteTime,
 		FileSizeHigh:   d.FileSizeHigh,
 		FileSizeLow:    d.FileSizeLow,
 	}
 	if d.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
 		// Per https://learn.microsoft.com/en-us/windows/win32/api/minwinbase/ns-minwinbase-win32_find_dataw:
 		// “If the dwFileAttributes member includes the FILE_ATTRIBUTE_REPARSE_POINT
 		// attribute, this member specifies the reparse point tag. Otherwise, this
 		// value is undefined and should not be used.”
 		fs.ReparseTag = d.Reserved0
 	}
 	return fs
 }

 // isReparseTagNameSurrogate determines whether a tag's associated
 // reparse point is a surrogate for another named entity (for example, a mounted folder).
 //
 // See https://learn.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-isreparsetagnamesurrogate
 // and https://learn.microsoft.com/en-us/windows/win32/fileio/reparse-point-tags.
 func (fs *fileStat) isReparseTagNameSurrogate() bool {
 	// True for IO_REPARSE_TAG_SYMLINK and IO_REPARSE_TAG_MOUNT_POINT.
 	return fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 && fs.ReparseTag&0x20000000 != 0
 }

 func (fs *fileStat) Size() int64 {
 	return int64(fs.FileSizeHigh)<<32 + int64(fs.FileSizeLow)
 }

 var winsymlink = godebug.New("winsymlink")

 func (fs *fileStat) Mode() FileMode {
 	m := fs.mode()
 	if winsymlink.Value() == "0" {
 		old := fs.modePreGo1_23()
 		if old != m {
 			winsymlink.IncNonDefault()
 			m = old
 		}
 	}
 	return m
 }

 func (fs *fileStat) mode() (m FileMode) {
 	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_READONLY != 0 {
 		m |= 0444
 	} else {
 		m |= 0666
 	}

 	// Windows reports the FILE_ATTRIBUTE_DIRECTORY bit for reparse points
 	// that refer to directories, such as symlinks and mount points.
 	// However, we follow symlink POSIX semantics and do not set the mode bits.
 	// This allows users to walk directories without following links
 	// by just calling "fi, err := os.Lstat(name); err == nil && fi.IsDir()".
 	// Note that POSIX only defines the semantics for symlinks, not for
 	// mount points or other surrogate reparse points, but we treat them
 	// the same way for consistency. Also, mount points can contain infinite
 	// loops, so it is not safe to walk them without special handling.
 	if !fs.isReparseTagNameSurrogate() {
 		if fs.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
 			m |= ModeDir | 0111
 		}

 		switch fs.filetype {
 		case syscall.FILE_TYPE_PIPE:
 			m |= ModeNamedPipe
 		case syscall.FILE_TYPE_CHAR:
 			m |= ModeDevice | ModeCharDevice
 		}
 	}

 	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
 		switch fs.ReparseTag {
 		case syscall.IO_REPARSE_TAG_SYMLINK:
 			m |= ModeSymlink
 		case windows.IO_REPARSE_TAG_AF_UNIX:
 			m |= ModeSocket
 		case windows.IO_REPARSE_TAG_DEDUP:
 			// If the Data Deduplication service is enabled on Windows Server, its
 			// Optimization job may convert regular files to IO_REPARSE_TAG_DEDUP
 			// whenever that job runs.
 			//
 			// However, DEDUP reparse points remain similar in most respects to
 			// regular files: they continue to support random-access reads and writes
 			// of persistent data, and they shouldn't add unexpected latency or
 			// unavailability in the way that a network filesystem might.
 			//
 			// Go programs may use ModeIrregular to filter out unusual files (such as
 			// raw device files on Linux, POSIX FIFO special files, and so on), so
 			// to avoid files changing unpredictably from regular to irregular we will
 			// consider DEDUP files to be close enough to regular to treat as such.
 		default:
 			m |= ModeIrregular
 		}
 	}
 	return
 }

 // modePreGo1_23 returns the FileMode for the fileStat, using the pre-Go 1.23
 // logic for determining the file mode.
 // The logic is subtle and not well-documented, so it is better to keep it
 // separate from the new logic.
 func (fs *fileStat) modePreGo1_23() (m FileMode) {
 	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_READONLY != 0 {
 		m |= 0444
 	} else {
 		m |= 0666
 	}
 	if fs.ReparseTag == syscall.IO_REPARSE_TAG_SYMLINK ||
 		fs.ReparseTag == windows.IO_REPARSE_TAG_MOUNT_POINT {
 		return m | ModeSymlink
 	}
 	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
 		m |= ModeDir | 0111
 	}
 	switch fs.filetype {
 	case syscall.FILE_TYPE_PIPE:
 		m |= ModeNamedPipe
 	case syscall.FILE_TYPE_CHAR:
 		m |= ModeDevice | ModeCharDevice
 	}
 	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
 		if fs.ReparseTag == windows.IO_REPARSE_TAG_AF_UNIX {
 			m |= ModeSocket
 		}
 		if m&ModeType == 0 {
 			if fs.ReparseTag == windows.IO_REPARSE_TAG_DEDUP {
 				// See comment in fs.Mode.
 			} else {
 				m |= ModeIrregular
 			}
 		}
 	}
 	return m
 }

 func (fs *fileStat) ModTime() time.Time {
 	return time.Unix(0, fs.LastWriteTime.Nanoseconds())
 }

 // Sys returns syscall.Win32FileAttributeData for file fs.
 func (fs *fileStat) Sys() any {
 	return &syscall.Win32FileAttributeData{
 		FileAttributes: fs.FileAttributes,
 		CreationTime:   fs.CreationTime,
 		LastAccessTime: fs.LastAccessTime,
 		LastWriteTime:  fs.LastWriteTime,
 		FileSizeHigh:   fs.FileSizeHigh,
 		FileSizeLow:    fs.FileSizeLow,
 	}
 }

 func (fs *fileStat) loadFileId() error {
 	fs.Lock()
 	defer fs.Unlock()
 	if fs.path == "" {
 		// already done
 		return nil
 	}
 	var path string
 	if fs.appendNameToPath {
 		path = fixLongPath(fs.path + `\` + fs.name)
 	} else {
 		path = fs.path
 	}
 	pathp, err := syscall.UTF16PtrFromString(path)
 	if err != nil {
 		return err
 	}

 	// Per https://learn.microsoft.com/en-us/windows/win32/fileio/reparse-points-and-file-operations,
 	// “Applications that use the CreateFile function should specify the
 	// FILE_FLAG_OPEN_REPARSE_POINT flag when opening the file if it is a reparse
 	// point.”
 	//
 	// And per https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew,
 	// “If the file is not a reparse point, then this flag is ignored.”
 	//
 	// So we set FILE_FLAG_OPEN_REPARSE_POINT unconditionally, since we want
 	// information about the reparse point itself.
 	//
 	// If the file is a symlink, the symlink target should have already been
 	// resolved when the fileStat was created, so we don't need to worry about
 	// resolving symlink reparse points again here.
 	attrs := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS | syscall.FILE_FLAG_OPEN_REPARSE_POINT)

 	h, err := syscall.CreateFile(pathp, 0, 0, nil, syscall.OPEN_EXISTING, attrs, 0)
 	if err != nil {
 		return err
 	}
 	defer syscall.CloseHandle(h)
 	var i syscall.ByHandleFileInformation
 	err = syscall.GetFileInformationByHandle(h, &i)
 	if err != nil {
 		return err
 	}
 	fs.path = ""
 	fs.vol = i.VolumeSerialNumber
 	fs.idxhi = i.FileIndexHigh
 	fs.idxlo = i.FileIndexLow
 	return nil
 }

 // saveInfoFromPath saves full path of the file to be used by os.SameFile later,
 // and set name from path.
 func (fs *fileStat) saveInfoFromPath(path string) error {
 	fs.path = path
 	if !filepathlite.IsAbs(fs.path) {
 		var err error
 		fs.path, err = syscall.FullPath(fs.path)
 		if err != nil {
 			return &PathError{Op: "FullPath", Path: path, Err: err}
 		}
 	}
 	fs.name = filepathlite.Base(path)
 	return nil
 }

 func sameFile(fs1, fs2 *fileStat) bool {
 	e := fs1.loadFileId()
 	if e != nil {
 		return false
 	}
 	e = fs2.loadFileId()
 	if e != nil {
 		return false
 	}
 	return fs1.vol == fs2.vol && fs1.idxhi == fs2.idxhi && fs1.idxlo == fs2.idxlo
 }

 // For testing.
 func atime(fi FileInfo) time.Time {
 	return time.Unix(0, fi.Sys().(*syscall.Win32FileAttributeData).LastAccessTime.Nanoseconds())
 }
	// 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 os

	import (
	"internal/filepathlite"
	"internal/godebug"
	"internal/syscall/windows"
	"sync"
	"syscall"
	"time"
	"unsafe"
	)

	// A fileStat is the implementation of FileInfo returned by Stat and Lstat.
	type fileStat struct {
	name string

	// from ByHandleFileInformation, Win32FileAttributeData, Win32finddata, and GetFileInformationByHandleEx
	FileAttributes uint32
	CreationTime syscall.Filetime
	LastAccessTime syscall.Filetime
	LastWriteTime syscall.Filetime
	FileSizeHigh uint32
	FileSizeLow uint32

	// from Win32finddata and GetFileInformationByHandleEx
	ReparseTag uint32

	// what syscall.GetFileType returns
	filetype uint32

	// used to implement SameFile
	sync.Mutex
	path string
	vol uint32
	idxhi uint32
	idxlo uint32
	appendNameToPath bool
	}

	// newFileStatFromGetFileInformationByHandle calls GetFileInformationByHandle
	// to gather all required information about the file handle h.
	func newFileStatFromGetFileInformationByHandle(path string, h syscall.Handle) (fs *fileStat, err error) {
	var d syscall.ByHandleFileInformation
	err = syscall.GetFileInformationByHandle(h, &d)
	if err != nil {
	return nil, &PathError{Op: "GetFileInformationByHandle", Path: path, Err: err}
	}

	var reparseTag uint32
	if d.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
	var ti windows.FILE_ATTRIBUTE_TAG_INFO
	err = windows.GetFileInformationByHandleEx(h, windows.FileAttributeTagInfo, (*byte)(unsafe.Pointer(&ti)), uint32(unsafe.Sizeof(ti)))
	if err != nil {
	return nil, &PathError{Op: "GetFileInformationByHandleEx", Path: path, Err: err}
	}
	reparseTag = ti.ReparseTag
	}

	return &fileStat{
	name: filepathlite.Base(path),
	FileAttributes: d.FileAttributes,
	CreationTime: d.CreationTime,
	LastAccessTime: d.LastAccessTime,
	LastWriteTime: d.LastWriteTime,
	FileSizeHigh: d.FileSizeHigh,
	FileSizeLow: d.FileSizeLow,
	vol: d.VolumeSerialNumber,
	idxhi: d.FileIndexHigh,
	idxlo: d.FileIndexLow,
	ReparseTag: reparseTag,
	// fileStat.path is used by os.SameFile to decide if it needs
	// to fetch vol, idxhi and idxlo. But these are already set,
	// so set fileStat.path to "" to prevent os.SameFile doing it again.
	}, nil
	}

	// newFileStatFromWin32FileAttributeData copies all required information
	// from syscall.Win32FileAttributeData d into the newly created fileStat.
	func newFileStatFromWin32FileAttributeData(d syscall.Win32FileAttributeData) fileStat {
	return &fileStat{
	FileAttributes: d.FileAttributes,
	CreationTime: d.CreationTime,
	LastAccessTime: d.LastAccessTime,
	LastWriteTime: d.LastWriteTime,
	FileSizeHigh: d.FileSizeHigh,
	FileSizeLow: d.FileSizeLow,
	}
	}

	// newFileStatFromFileIDBothDirInfo copies all required information
	// from windows.FILE_ID_BOTH_DIR_INFO d into the newly created fileStat.
	func newFileStatFromFileIDBothDirInfo(d windows.FILE_ID_BOTH_DIR_INFO) fileStat {
	// The FILE_ID_BOTH_DIR_INFO MSDN documentations isn't completely correct.
	// FileAttributes can contain any file attributes that is currently set on the file,
	// not just the ones documented.
	// EaSize contains the reparse tag if the file is a reparse point.
	return &fileStat{
	FileAttributes: d.FileAttributes,
	CreationTime: d.CreationTime,
	LastAccessTime: d.LastAccessTime,
	LastWriteTime: d.LastWriteTime,
	FileSizeHigh: uint32(d.EndOfFile >> 32),
	FileSizeLow: uint32(d.EndOfFile),
	ReparseTag: d.EaSize,
	idxhi: uint32(d.FileID >> 32),
	idxlo: uint32(d.FileID),
	}
	}

	// newFileStatFromFileFullDirInfo copies all required information
	// from windows.FILE_FULL_DIR_INFO d into the newly created fileStat.
	func newFileStatFromFileFullDirInfo(d windows.FILE_FULL_DIR_INFO) fileStat {
	return &fileStat{
	FileAttributes: d.FileAttributes,
	CreationTime: d.CreationTime,
	LastAccessTime: d.LastAccessTime,
	LastWriteTime: d.LastWriteTime,
	FileSizeHigh: uint32(d.EndOfFile >> 32),
	FileSizeLow: uint32(d.EndOfFile),
	ReparseTag: d.EaSize,
	}
	}

	// newFileStatFromWin32finddata copies all required information
	// from syscall.Win32finddata d into the newly created fileStat.
	func newFileStatFromWin32finddata(d syscall.Win32finddata) fileStat {
	fs := &fileStat{
	FileAttributes: d.FileAttributes,
	CreationTime: d.CreationTime,
	LastAccessTime: d.LastAccessTime,
	LastWriteTime: d.LastWriteTime,
	FileSizeHigh: d.FileSizeHigh,
	FileSizeLow: d.FileSizeLow,
	}
	if d.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
	// Per https://learn.microsoft.com/en-us/windows/win32/api/minwinbase/ns-minwinbase-win32_find_dataw:
	// “If the dwFileAttributes member includes the FILE_ATTRIBUTE_REPARSE_POINT
	// attribute, this member specifies the reparse point tag. Otherwise, this
	// value is undefined and should not be used.”
	fs.ReparseTag = d.Reserved0
	}
	return fs
	}

	// isReparseTagNameSurrogate determines whether a tag's associated
	// reparse point is a surrogate for another named entity (for example, a mounted folder).
	//
	// See https://learn.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-isreparsetagnamesurrogate
	// and https://learn.microsoft.com/en-us/windows/win32/fileio/reparse-point-tags.
	func (fs *fileStat) isReparseTagNameSurrogate() bool {
	// True for IO_REPARSE_TAG_SYMLINK and IO_REPARSE_TAG_MOUNT_POINT.
	return fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 && fs.ReparseTag&0x20000000 != 0
	}

	func (fs *fileStat) Size() int64 {
	return int64(fs.FileSizeHigh)<<32 + int64(fs.FileSizeLow)
	}

	var winsymlink = godebug.New("winsymlink")

	func (fs *fileStat) Mode() FileMode {
	m := fs.mode()
	if winsymlink.Value() == "0" {
	old := fs.modePreGo1_23()
	if old != m {
	winsymlink.IncNonDefault()
	m = old
	}
	}
	return m
	}

	func (fs *fileStat) mode() (m FileMode) {
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_READONLY != 0 {
	m \|= 0444
	} else {
	m \|= 0666
	}

	// Windows reports the FILE_ATTRIBUTE_DIRECTORY bit for reparse points
	// that refer to directories, such as symlinks and mount points.
	// However, we follow symlink POSIX semantics and do not set the mode bits.
	// This allows users to walk directories without following links
	// by just calling "fi, err := os.Lstat(name); err == nil && fi.IsDir()".
	// Note that POSIX only defines the semantics for symlinks, not for
	// mount points or other surrogate reparse points, but we treat them
	// the same way for consistency. Also, mount points can contain infinite
	// loops, so it is not safe to walk them without special handling.
	if !fs.isReparseTagNameSurrogate() {
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
	m \|= ModeDir \| 0111
	}

	switch fs.filetype {
	case syscall.FILE_TYPE_PIPE:
	m \|= ModeNamedPipe
	case syscall.FILE_TYPE_CHAR:
	m \|= ModeDevice \| ModeCharDevice
	}
	}

	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
	switch fs.ReparseTag {
	case syscall.IO_REPARSE_TAG_SYMLINK:
	m \|= ModeSymlink
	case windows.IO_REPARSE_TAG_AF_UNIX:
	m \|= ModeSocket
	case windows.IO_REPARSE_TAG_DEDUP:
	// If the Data Deduplication service is enabled on Windows Server, its
	// Optimization job may convert regular files to IO_REPARSE_TAG_DEDUP
	// whenever that job runs.
	//
	// However, DEDUP reparse points remain similar in most respects to
	// regular files: they continue to support random-access reads and writes
	// of persistent data, and they shouldn't add unexpected latency or
	// unavailability in the way that a network filesystem might.
	//
	// Go programs may use ModeIrregular to filter out unusual files (such as
	// raw device files on Linux, POSIX FIFO special files, and so on), so
	// to avoid files changing unpredictably from regular to irregular we will
	// consider DEDUP files to be close enough to regular to treat as such.
	default:
	m \|= ModeIrregular
	}
	}
	return
	}

	// modePreGo1_23 returns the FileMode for the fileStat, using the pre-Go 1.23
	// logic for determining the file mode.
	// The logic is subtle and not well-documented, so it is better to keep it
	// separate from the new logic.
	func (fs *fileStat) modePreGo1_23() (m FileMode) {
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_READONLY != 0 {
	m \|= 0444
	} else {
	m \|= 0666
	}
	if fs.ReparseTag == syscall.IO_REPARSE_TAG_SYMLINK \|\|
	fs.ReparseTag == windows.IO_REPARSE_TAG_MOUNT_POINT {
	return m \| ModeSymlink
	}
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
	m \|= ModeDir \| 0111
	}
	switch fs.filetype {
	case syscall.FILE_TYPE_PIPE:
	m \|= ModeNamedPipe
	case syscall.FILE_TYPE_CHAR:
	m \|= ModeDevice \| ModeCharDevice
	}
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
	if fs.ReparseTag == windows.IO_REPARSE_TAG_AF_UNIX {
	m \|= ModeSocket
	}
	if m&ModeType == 0 {
	if fs.ReparseTag == windows.IO_REPARSE_TAG_DEDUP {
	// See comment in fs.Mode.
	} else {
	m \|= ModeIrregular
	}
	}
	}
	return m
	}

	func (fs *fileStat) ModTime() time.Time {
	return time.Unix(0, fs.LastWriteTime.Nanoseconds())
	}

	// Sys returns syscall.Win32FileAttributeData for file fs.
	func (fs *fileStat) Sys() any {
	return &syscall.Win32FileAttributeData{
	FileAttributes: fs.FileAttributes,
	CreationTime: fs.CreationTime,
	LastAccessTime: fs.LastAccessTime,
	LastWriteTime: fs.LastWriteTime,
	FileSizeHigh: fs.FileSizeHigh,
	FileSizeLow: fs.FileSizeLow,
	}
	}

	func (fs *fileStat) loadFileId() error {
	fs.Lock()
	defer fs.Unlock()
	if fs.path == "" {
	// already done
	return nil
	}
	var path string
	if fs.appendNameToPath {
	path = fixLongPath(fs.path + `\` + fs.name)
	} else {
	path = fs.path
	}
	pathp, err := syscall.UTF16PtrFromString(path)
	if err != nil {
	return err
	}

	// Per https://learn.microsoft.com/en-us/windows/win32/fileio/reparse-points-and-file-operations,
	// “Applications that use the CreateFile function should specify the
	// FILE_FLAG_OPEN_REPARSE_POINT flag when opening the file if it is a reparse
	// point.”
	//
	// And per https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew,
	// “If the file is not a reparse point, then this flag is ignored.”
	//
	// So we set FILE_FLAG_OPEN_REPARSE_POINT unconditionally, since we want
	// information about the reparse point itself.
	//
	// If the file is a symlink, the symlink target should have already been
	// resolved when the fileStat was created, so we don't need to worry about
	// resolving symlink reparse points again here.
	attrs := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS \| syscall.FILE_FLAG_OPEN_REPARSE_POINT)

	h, err := syscall.CreateFile(pathp, 0, 0, nil, syscall.OPEN_EXISTING, attrs, 0)
	if err != nil {
	return err
	}
	defer syscall.CloseHandle(h)
	var i syscall.ByHandleFileInformation
	err = syscall.GetFileInformationByHandle(h, &i)
	if err != nil {
	return err
	}
	fs.path = ""
	fs.vol = i.VolumeSerialNumber
	fs.idxhi = i.FileIndexHigh
	fs.idxlo = i.FileIndexLow
	return nil
	}

	// saveInfoFromPath saves full path of the file to be used by os.SameFile later,
	// and set name from path.
	func (fs *fileStat) saveInfoFromPath(path string) error {
	fs.path = path
	if !filepathlite.IsAbs(fs.path) {
	var err error
	fs.path, err = syscall.FullPath(fs.path)
	if err != nil {
	return &PathError{Op: "FullPath", Path: path, Err: err}
	}
	}
	fs.name = filepathlite.Base(path)
	return nil
	}

	func sameFile(fs1, fs2 *fileStat) bool {
	e := fs1.loadFileId()
	if e != nil {
	return false
	}
	e = fs2.loadFileId()
	if e != nil {
	return false
	}
	return fs1.vol == fs2.vol && fs1.idxhi == fs2.idxhi && fs1.idxlo == fs2.idxlo
	}

	// For testing.
	func atime(fi FileInfo) time.Time {
	return time.Unix(0, fi.Sys().(*syscall.Win32FileAttributeData).LastAccessTime.Nanoseconds())
	}