patch os: File

internal/lib/os/file.go

@@ -217,6 +217,7 @@ func setStickyBit(name string) error {
 	}
 	return Chmod(name, fi.Mode()|ModeSticky)
 }
+*/
 
 // Open opens the named file for reading. If successful, methods on
 // the returned file can be used for reading; the associated file
@@ -242,7 +243,6 @@ func Create(name string) (*File, error) {
 // methods on the returned File can be used for I/O.
 // If there is an error, it will be of type *PathError.
 func OpenFile(name string, flag int, perm FileMode) (*File, error) {
-	testlog.Open(name)
 	f, err := openFileNolog(name, flag, perm)
 	if err != nil {
 		return nil, err
@@ -252,6 +252,7 @@ func OpenFile(name string, flag int, perm FileMode) (*File, error) {
 	return f, nil
 }
 
+/*
 // lstat is overridden in tests.
 var lstat = Lstat
 

internal/lib/os/file_unix.go

@@ -0,0 +1,199 @@
+// 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.
+
+//go:build unix || (js && wasm) || wasip1
+
+package os
+
+import (
+	"io/fs"
+	"runtime"
+)
+
+// Fd returns the integer Unix file descriptor referencing the open file.
+// If f is closed, the file descriptor becomes invalid.
+// If f is garbage collected, a finalizer may close the file descriptor,
+// making it invalid; see runtime.SetFinalizer for more information on when
+// a finalizer might be run. On Unix systems this will cause the SetDeadline
+// methods to stop working.
+// Because file descriptors can be reused, the returned file descriptor may
+// only be closed through the Close method of f, or by its finalizer during
+// garbage collection. Otherwise, during garbage collection the finalizer
+// may close an unrelated file descriptor with the same (reused) number.
+//
+// As an alternative, see the f.SyscallConn method.
+func (f *File) Fd() uintptr {
+	if f == nil {
+		return ^(uintptr(0))
+	}
+
+	return f.fd
+}
+
+// NewFile returns a new File with the given file descriptor and
+// name. The returned value will be nil if fd is not a valid file
+// descriptor. On Unix systems, if the file descriptor is in
+// non-blocking mode, NewFile will attempt to return a pollable File
+// (one for which the SetDeadline methods work).
+//
+// After passing it to NewFile, fd may become invalid under the same
+// conditions described in the comments of the Fd method, and the same
+// constraints apply.
+func NewFile(fd uintptr, name string) *File {
+	return &File{fd: fd, name: name}
+}
+
+/* TODO(xsw):
+// NewFile returns a new File with the given file descriptor and
+// name. The returned value will be nil if fd is not a valid file
+// descriptor. On Unix systems, if the file descriptor is in
+// non-blocking mode, NewFile will attempt to return a pollable File
+// (one for which the SetDeadline methods work).
+//
+// After passing it to NewFile, fd may become invalid under the same
+// conditions described in the comments of the Fd method, and the same
+// constraints apply.
+func NewFile(fd uintptr, name string) *File {
+	fdi := int(fd)
+	if fdi < 0 {
+		return nil
+	}
+
+	kind := kindNewFile
+	appendMode := false
+	if flags, err := unix.Fcntl(fdi, syscall.F_GETFL, 0); err == nil {
+		if unix.HasNonblockFlag(flags) {
+			kind = kindNonBlock
+		}
+		appendMode = flags&syscall.O_APPEND != 0
+	}
+	f := newFile(fdi, name, kind)
+	f.appendMode = appendMode
+	return f
+}
+
+// net_newUnixFile is a hidden entry point called by net.conn.File.
+// This is used so that a nonblocking network connection will become
+// blocking if code calls the Fd method. We don't want that for direct
+// calls to NewFile: passing a nonblocking descriptor to NewFile should
+// remain nonblocking if you get it back using Fd. But for net.conn.File
+// the call to NewFile is hidden from the user. Historically in that case
+// the Fd method has returned a blocking descriptor, and we want to
+// retain that behavior because existing code expects it and depends on it.
+//
+//-go:linkname net_newUnixFile net.newUnixFile
+func net_newUnixFile(fd int, name string) *File {
+	if fd < 0 {
+		panic("invalid FD")
+	}
+
+	f := newFile(fd, name, kindNonBlock)
+	f.nonblock = true // tell Fd to return blocking descriptor
+	return f
+}
+*/
+
+// newFileKind describes the kind of file to newFile.
+type newFileKind int
+
+const (
+	// kindNewFile means that the descriptor was passed to us via NewFile.
+	kindNewFile newFileKind = iota
+	// kindOpenFile means that the descriptor was opened using
+	// Open, Create, or OpenFile (without O_NONBLOCK).
+	kindOpenFile
+	// kindPipe means that the descriptor was opened using Pipe.
+	kindPipe
+	// kindNonBlock means that the descriptor is already in
+	// non-blocking mode.
+	kindNonBlock
+	// kindNoPoll means that we should not put the descriptor into
+	// non-blocking mode, because we know it is not a pipe or FIFO.
+	// Used by openFdAt for directories.
+	kindNoPoll
+)
+
+// TODO(xsw):
+// func sigpipe() // implemented in package runtime
+
+// epipecheck raises SIGPIPE if we get an EPIPE error on standard
+// output or standard error. See the SIGPIPE docs in os/signal, and
+// issue 11845.
+func epipecheck(file *File, e error) {
+	/* TODO(xsw):
+	if e == syscall.EPIPE && file.stdoutOrErr {
+		sigpipe()
+	}
+	*/
+	panic("todo: os.epipecheck")
+}
+
+// DevNull is the name of the operating system's “null device.”
+// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
+const DevNull = "/dev/null"
+
+// openFileNolog is the Unix implementation of OpenFile.
+// Changes here should be reflected in openFdAt, if relevant.
+func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
+	panic("todo: os.openFileNolog")
+}
+
+func tempDir() string {
+	dir := Getenv("TMPDIR")
+	if dir == "" {
+		if runtime.GOOS == "android" {
+			dir = "/data/local/tmp"
+		} else {
+			dir = "/tmp"
+		}
+	}
+	return dir
+}
+
+type unixDirent struct {
+	parent string
+	name   string
+	typ    FileMode
+	info   FileInfo
+}
+
+func (d *unixDirent) Name() string   { return d.name }
+func (d *unixDirent) IsDir() bool    { return d.typ.IsDir() }
+func (d *unixDirent) Type() FileMode { return d.typ }
+
+func (d *unixDirent) Info() (FileInfo, error) {
+	/* TODO(xsw):
+	if d.info != nil {
+		return d.info, nil
+	}
+	return lstat(d.parent + "/" + d.name)
+	*/
+	panic("todo: os.unixDirent.Info")
+}
+
+func (d *unixDirent) String() string {
+	return fs.FormatDirEntry(d)
+}
+
+/* TODO(xsw):
+func newUnixDirent(parent, name string, typ FileMode) (DirEntry, error) {
+	ude := &unixDirent{
+		parent: parent,
+		name:   name,
+		typ:    typ,
+	}
+	if typ != ^FileMode(0) && !testingForceReadDirLstat {
+		return ude, nil
+	}
+
+	info, err := lstat(parent + "/" + name)
+	if err != nil {
+		return nil, err
+	}
+
+	ude.typ = info.Mode().Type()
+	ude.info = info
+	return ude, nil
+}
+*/

internal/lib/os/os.go

@@ -202,7 +202,6 @@ func Getwd() (dir string, err error) {
 // func Hostname() (name string, err error)
 // func IsExist(err error) bool
 // func IsNotExist(err error) bool
-// func IsPathSeparator(c uint8) bool
 // func IsPermission(err error) bool
 // func IsTimeout(err error) bool
 

internal/lib/os/path_plan9.go

@@ -0,0 +1,19 @@
+// Copyright 2011 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
+
+const (
+	PathSeparator     = '/'    // OS-specific path separator
+	PathListSeparator = '\000' // OS-specific path list separator
+)
+
+// IsPathSeparator reports whether c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	return PathSeparator == c
+}
+
+func fixRootDirectory(p string) string {
+	return p
+}

internal/lib/os/path_unix.go

@@ -0,0 +1,75 @@
+// Copyright 2011 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.
+
+//go:build unix || (js && wasm) || wasip1
+
+package os
+
+const (
+	PathSeparator     = '/' // OS-specific path separator
+	PathListSeparator = ':' // OS-specific path list separator
+)
+
+// IsPathSeparator reports whether c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	return PathSeparator == c
+}
+
+// basename removes trailing slashes and the leading directory name from path name.
+func basename(name string) string {
+	i := len(name) - 1
+	// Remove trailing slashes
+	for ; i > 0 && name[i] == '/'; i-- {
+		name = name[:i]
+	}
+	// Remove leading directory name
+	for i--; i >= 0; i-- {
+		if name[i] == '/' {
+			name = name[i+1:]
+			break
+		}
+	}
+
+	return name
+}
+
+// splitPath returns the base name and parent directory.
+func splitPath(path string) (string, string) {
+	// if no better parent is found, the path is relative from "here"
+	dirname := "."
+
+	// Remove all but one leading slash.
+	for len(path) > 1 && path[0] == '/' && path[1] == '/' {
+		path = path[1:]
+	}
+
+	i := len(path) - 1
+
+	// Remove trailing slashes.
+	for ; i > 0 && path[i] == '/'; i-- {
+		path = path[:i]
+	}
+
+	// if no slashes in path, base is path
+	basename := path
+
+	// Remove leading directory path
+	for i--; i >= 0; i-- {
+		if path[i] == '/' {
+			if i == 0 {
+				dirname = path[:1]
+			} else {
+				dirname = path[:i]
+			}
+			basename = path[i+1:]
+			break
+		}
+	}
+
+	return dirname, basename
+}
+
+func fixRootDirectory(p string) string {
+	return p
+}

internal/lib/os/path_windows.go

@@ -0,0 +1,227 @@
+// Copyright 2011 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
+
+const (
+	PathSeparator     = '\\' // OS-specific path separator
+	PathListSeparator = ';'  // OS-specific path list separator
+)
+
+// IsPathSeparator reports whether c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	// NOTE: Windows accepts / as path separator.
+	return c == '\\' || c == '/'
+}
+
+// basename removes trailing slashes and the leading
+// directory name and drive letter from path name.
+func basename(name string) string {
+	// Remove drive letter
+	if len(name) == 2 && name[1] == ':' {
+		name = "."
+	} else if len(name) > 2 && name[1] == ':' {
+		name = name[2:]
+	}
+	i := len(name) - 1
+	// Remove trailing slashes
+	for ; i > 0 && (name[i] == '/' || name[i] == '\\'); i-- {
+		name = name[:i]
+	}
+	// Remove leading directory name
+	for i--; i >= 0; i-- {
+		if name[i] == '/' || name[i] == '\\' {
+			name = name[i+1:]
+			break
+		}
+	}
+	return name
+}
+
+func isAbs(path string) (b bool) {
+	v := volumeName(path)
+	if v == "" {
+		return false
+	}
+	path = path[len(v):]
+	if path == "" {
+		return false
+	}
+	return IsPathSeparator(path[0])
+}
+
+func volumeName(path string) (v string) {
+	if len(path) < 2 {
+		return ""
+	}
+	// with drive letter
+	c := path[0]
+	if path[1] == ':' &&
+		('0' <= c && c <= '9' || 'a' <= c && c <= 'z' ||
+			'A' <= c && c <= 'Z') {
+		return path[:2]
+	}
+	// is it UNC
+	if l := len(path); l >= 5 && IsPathSeparator(path[0]) && IsPathSeparator(path[1]) &&
+		!IsPathSeparator(path[2]) && path[2] != '.' {
+		// first, leading `\\` and next shouldn't be `\`. its server name.
+		for n := 3; n < l-1; n++ {
+			// second, next '\' shouldn't be repeated.
+			if IsPathSeparator(path[n]) {
+				n++
+				// third, following something characters. its share name.
+				if !IsPathSeparator(path[n]) {
+					if path[n] == '.' {
+						break
+					}
+					for ; n < l; n++ {
+						if IsPathSeparator(path[n]) {
+							break
+						}
+					}
+					return path[:n]
+				}
+				break
+			}
+		}
+	}
+	return ""
+}
+
+func fromSlash(path string) string {
+	// Replace each '/' with '\\' if present
+	var pathbuf []byte
+	var lastSlash int
+	for i, b := range path {
+		if b == '/' {
+			if pathbuf == nil {
+				pathbuf = make([]byte, len(path))
+			}
+			copy(pathbuf[lastSlash:], path[lastSlash:i])
+			pathbuf[i] = '\\'
+			lastSlash = i + 1
+		}
+	}
+	if pathbuf == nil {
+		return path
+	}
+
+	copy(pathbuf[lastSlash:], path[lastSlash:])
+	return string(pathbuf)
+}
+
+func dirname(path string) string {
+	vol := volumeName(path)
+	i := len(path) - 1
+	for i >= len(vol) && !IsPathSeparator(path[i]) {
+		i--
+	}
+	dir := path[len(vol) : i+1]
+	last := len(dir) - 1
+	if last > 0 && IsPathSeparator(dir[last]) {
+		dir = dir[:last]
+	}
+	if dir == "" {
+		dir = "."
+	}
+	return vol + dir
+}
+
+// This is set via go:linkname on runtime.canUseLongPaths, and is true when the OS
+// supports opting into proper long path handling without the need for fixups.
+var canUseLongPaths bool
+
+// fixLongPath returns the extended-length (\\?\-prefixed) form of
+// path when needed, in order to avoid the default 260 character file
+// path limit imposed by Windows. If path is not easily converted to
+// the extended-length form (for example, if path is a relative path
+// or contains .. elements), or is short enough, fixLongPath returns
+// path unmodified.
+//
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
+func fixLongPath(path string) string {
+	if canUseLongPaths {
+		return path
+	}
+	// Do nothing (and don't allocate) if the path is "short".
+	// Empirically (at least on the Windows Server 2013 builder),
+	// the kernel is arbitrarily okay with < 248 bytes. That
+	// matches what the docs above say:
+	// "When using an API to create a directory, the specified
+	// path cannot be so long that you cannot append an 8.3 file
+	// name (that is, the directory name cannot exceed MAX_PATH
+	// minus 12)." Since MAX_PATH is 260, 260 - 12 = 248.
+	//
+	// The MSDN docs appear to say that a normal path that is 248 bytes long
+	// will work; empirically the path must be less then 248 bytes long.
+	if len(path) < 248 {
+		// Don't fix. (This is how Go 1.7 and earlier worked,
+		// not automatically generating the \\?\ form)
+		return path
+	}
+
+	// The extended form begins with \\?\, as in
+	// \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
+	// The extended form disables evaluation of . and .. path
+	// elements and disables the interpretation of / as equivalent
+	// to \. The conversion here rewrites / to \ and elides
+	// . elements as well as trailing or duplicate separators. For
+	// simplicity it avoids the conversion entirely for relative
+	// paths or paths containing .. elements. For now,
+	// \\server\share paths are not converted to
+	// \\?\UNC\server\share paths because the rules for doing so
+	// are less well-specified.
+	if len(path) >= 2 && path[:2] == `\\` {
+		// Don't canonicalize UNC paths.
+		return path
+	}
+	if !isAbs(path) {
+		// Relative path
+		return path
+	}
+
+	const prefix = `\\?`
+
+	pathbuf := make([]byte, len(prefix)+len(path)+len(`\`))
+	copy(pathbuf, prefix)
+	n := len(path)
+	r, w := 0, len(prefix)
+	for r < n {
+		switch {
+		case IsPathSeparator(path[r]):
+			// empty block
+			r++
+		case path[r] == '.' && (r+1 == n || IsPathSeparator(path[r+1])):
+			// /./
+			r++
+		case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || IsPathSeparator(path[r+2])):
+			// /../ is currently unhandled
+			return path
+		default:
+			pathbuf[w] = '\\'
+			w++
+			for ; r < n && !IsPathSeparator(path[r]); r++ {
+				pathbuf[w] = path[r]
+				w++
+			}
+		}
+	}
+	// A drive's root directory needs a trailing \
+	if w == len(`\\?\c:`) {
+		pathbuf[w] = '\\'
+		w++
+	}
+	return string(pathbuf[:w])
+}
+
+// fixRootDirectory fixes a reference to a drive's root directory to
+// have the required trailing slash.
+func fixRootDirectory(p string) string {
+	if len(p) == len(`\\?\c:`) {
+		if IsPathSeparator(p[0]) && IsPathSeparator(p[1]) && p[2] == '?' && IsPathSeparator(p[3]) && p[5] == ':' {
+			return p + `\`
+		}
+	}
+	return p
+}

internal/lib/os/stat.go

@@ -0,0 +1,19 @@
+// Copyright 2017 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
+
+// Stat returns a FileInfo describing the named file.
+// If there is an error, it will be of type *PathError.
+func Stat(name string) (FileInfo, error) {
+	return statNolog(name)
+}
+
+// Lstat returns a FileInfo describing the named file.
+// If the file is a symbolic link, the returned FileInfo
+// describes the symbolic link. Lstat makes no attempt to follow the link.
+// If there is an error, it will be of type *PathError.
+func Lstat(name string) (FileInfo, error) {
+	return lstatNolog(name)
+}

internal/lib/os/stat_darwin.go

@@ -0,0 +1,42 @@
+// 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 (
+	"syscall"
+	"time"
+)
+
+func fillFileStatFromSys(fs *fileStat, name string) {
+	fs.name = basename(name)
+	fs.size = fs.sys.Size
+	fs.modTime = time.Unix(fs.sys.Mtimespec.Unix())
+	fs.mode = FileMode(fs.sys.Mode & 0777)
+	switch fs.sys.Mode & syscall.S_IFMT {
+	case syscall.S_IFBLK, syscall.S_IFWHT:
+		fs.mode |= ModeDevice
+	case syscall.S_IFCHR:
+		fs.mode |= ModeDevice | ModeCharDevice
+	case syscall.S_IFDIR:
+		fs.mode |= ModeDir
+	case syscall.S_IFIFO:
+		fs.mode |= ModeNamedPipe
+	case syscall.S_IFLNK:
+		fs.mode |= ModeSymlink
+	case syscall.S_IFREG:
+		// nothing to do
+	case syscall.S_IFSOCK:
+		fs.mode |= ModeSocket
+	}
+	if fs.sys.Mode&syscall.S_ISGID != 0 {
+		fs.mode |= ModeSetgid
+	}
+	if fs.sys.Mode&syscall.S_ISUID != 0 {
+		fs.mode |= ModeSetuid
+	}
+	if fs.sys.Mode&syscall.S_ISVTX != 0 {
+		fs.mode |= ModeSticky
+	}
+}

internal/lib/os/stat_linux.go

@@ -0,0 +1,42 @@
+// 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 (
+	"syscall"
+	"time"
+)
+
+func fillFileStatFromSys(fs *fileStat, name string) {
+	fs.name = basename(name)
+	fs.size = fs.sys.Size
+	fs.modTime = time.Unix(fs.sys.Mtim.Unix())
+	fs.mode = FileMode(fs.sys.Mode & 0777)
+	switch fs.sys.Mode & syscall.S_IFMT {
+	case syscall.S_IFBLK:
+		fs.mode |= ModeDevice
+	case syscall.S_IFCHR:
+		fs.mode |= ModeDevice | ModeCharDevice
+	case syscall.S_IFDIR:
+		fs.mode |= ModeDir
+	case syscall.S_IFIFO:
+		fs.mode |= ModeNamedPipe
+	case syscall.S_IFLNK:
+		fs.mode |= ModeSymlink
+	case syscall.S_IFREG:
+		// nothing to do
+	case syscall.S_IFSOCK:
+		fs.mode |= ModeSocket
+	}
+	if fs.sys.Mode&syscall.S_ISGID != 0 {
+		fs.mode |= ModeSetgid
+	}
+	if fs.sys.Mode&syscall.S_ISUID != 0 {
+		fs.mode |= ModeSetuid
+	}
+	if fs.sys.Mode&syscall.S_ISVTX != 0 {
+		fs.mode |= ModeSticky
+	}
+}

internal/lib/os/stat_unix.go

@@ -0,0 +1,57 @@
+// Copyright 2016 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.
+
+//go:build unix || (js && wasm) || wasip1
+
+package os
+
+// Stat returns the FileInfo structure describing file.
+// If there is an error, it will be of type *PathError.
+func (f *File) Stat() (FileInfo, error) {
+	/* TODO(xsw):
+	if f == nil {
+		return nil, ErrInvalid
+	}
+	var fs fileStat
+	err := os.Fstat(c.Int(f.fd), &fs.sys)
+	if err != 0 {
+		return nil, &PathError{Op: "stat", Path: f.name, Err: syscall.Errno(err)}
+	}
+	fillFileStatFromSys(&fs, f.name)
+	return &fs, nil
+	*/
+	panic("todo: os.File.Stat")
+}
+
+// statNolog stats a file with no test logging.
+func statNolog(name string) (FileInfo, error) {
+	/* TODO(xsw):
+	var fs fileStat
+	err := ignoringEINTR(func() error {
+		return syscall.Stat(name, &fs.sys)
+	})
+	if err != nil {
+		return nil, &PathError{Op: "stat", Path: name, Err: err}
+	}
+	fillFileStatFromSys(&fs, name)
+	return &fs, nil
+	*/
+	panic("todo: os.statNolog")
+}
+
+// lstatNolog lstats a file with no test logging.
+func lstatNolog(name string) (FileInfo, error) {
+	/* TODO(xsw):
+	var fs fileStat
+	err := ignoringEINTR(func() error {
+		return syscall.Lstat(name, &fs.sys)
+	})
+	if err != nil {
+		return nil, &PathError{Op: "lstat", Path: name, Err: err}
+	}
+	fillFileStatFromSys(&fs, name)
+	return &fs, nil
+	*/
+	panic("todo: os.lstatNolog")
+}

internal/lib/os/types.go

@@ -22,19 +22,7 @@ type File struct {
 	fd         uintptr
 	name       string
 	appendMode bool
-}
-
-// NewFile returns a new File with the given file descriptor and
-// name. The returned value will be nil if fd is not a valid file
-// descriptor. On Unix systems, if the file descriptor is in
-// non-blocking mode, NewFile will attempt to return a pollable File
-// (one for which the SetDeadline methods work).
-//
-// After passing it to NewFile, fd may become invalid under the same
-// conditions described in the comments of the Fd method, and the same
-// constraints apply.
-func NewFile(fd uintptr, name string) *File {
-	return &File{fd: fd, name: name}
+	nonblock   bool
 }
 
 // write writes len(b) bytes to the File.
@@ -118,10 +106,8 @@ const (
 	ModePerm = fs.ModePerm // Unix permission bits, 0o777
 )
 
-/* TODO(xsw):
 func (fs *fileStat) Name() string { return fs.name }
 func (fs *fileStat) IsDir() bool  { return fs.Mode().IsDir() }
-*/
 
 // SameFile reports whether fi1 and fi2 describe the same file.
 // For example, on Unix this means that the device and inode fields
@@ -130,13 +116,10 @@ func (fs *fileStat) IsDir() bool  { return fs.Mode().IsDir() }
 // SameFile only applies to results returned by this package's Stat.
 // It returns false in other cases.
 func SameFile(fi1, fi2 FileInfo) bool {
-	/*
-		fs1, ok1 := fi1.(*fileStat)
-		fs2, ok2 := fi2.(*fileStat)
-		if !ok1 || !ok2 {
-			return false
-		}
-		return sameFile(fs1, fs2)
-	*/
-	panic("todo")
+	fs1, ok1 := fi1.(*fileStat)
+	fs2, ok2 := fi2.(*fileStat)
+	if !ok1 || !ok2 {
+		return false
+	}
+	return sameFile(fs1, fs2)
 }

internal/lib/os/types_plan9.go

@@ -0,0 +1,30 @@
+// 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 (
+	"syscall"
+	"time"
+)
+
+// A fileStat is the implementation of FileInfo returned by Stat and Lstat.
+type fileStat struct {
+	name    string
+	size    int64
+	mode    FileMode
+	modTime time.Time
+	sys     any
+}
+
+func (fs *fileStat) Size() int64        { return fs.size }
+func (fs *fileStat) Mode() FileMode     { return fs.mode }
+func (fs *fileStat) ModTime() time.Time { return fs.modTime }
+func (fs *fileStat) Sys() any           { return fs.sys }
+
+func sameFile(fs1, fs2 *fileStat) bool {
+	a := fs1.sys.(*syscall.Dir)
+	b := fs2.sys.(*syscall.Dir)
+	return a.Qid.Path == b.Qid.Path && a.Type == b.Type && a.Dev == b.Dev
+}

internal/lib/os/types_unix.go

@@ -0,0 +1,30 @@
+// 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.
+
+//go:build !windows && !plan9
+
+package os
+
+import (
+	"syscall"
+	"time"
+)
+
+// A fileStat is the implementation of FileInfo returned by Stat and Lstat.
+type fileStat struct {
+	name    string
+	size    int64
+	mode    FileMode
+	modTime time.Time
+	sys     syscall.Stat_t
+}
+
+func (fs *fileStat) Size() int64        { return fs.size }
+func (fs *fileStat) Mode() FileMode     { return fs.mode }
+func (fs *fileStat) ModTime() time.Time { return fs.modTime }
+func (fs *fileStat) Sys() any           { return &fs.sys }
+
+func sameFile(fs1, fs2 *fileStat) bool {
+	return fs1.sys.Dev == fs2.sys.Dev && fs1.sys.Ino == fs2.sys.Ino
+}

internal/lib/os/types_windows.go

@@ -0,0 +1,241 @@
+// 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/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 and Win32finddata
+	FileAttributes uint32
+	CreationTime   syscall.Filetime
+	LastAccessTime syscall.Filetime
+	LastWriteTime  syscall.Filetime
+	FileSizeHigh   uint32
+	FileSizeLow    uint32
+
+	// from Win32finddata
+	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 ti windows.FILE_ATTRIBUTE_TAG_INFO
+	err = windows.GetFileInformationByHandleEx(h, windows.FileAttributeTagInfo, (*byte)(unsafe.Pointer(&ti)), uint32(unsafe.Sizeof(ti)))
+	if err != nil {
+		if errno, ok := err.(syscall.Errno); ok && errno == windows.ERROR_INVALID_PARAMETER {
+			// It appears calling GetFileInformationByHandleEx with
+			// FILE_ATTRIBUTE_TAG_INFO fails on FAT file system with
+			// ERROR_INVALID_PARAMETER. Clear ti.ReparseTag in that
+			// instance to indicate no symlinks are possible.
+			ti.ReparseTag = 0
+		} else {
+			return nil, &PathError{Op: "GetFileInformationByHandleEx", Path: path, Err: err}
+		}
+	}
+
+	return &fileStat{
+		name:           basename(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:     ti.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
+}
+
+// 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
+}
+
+func (fs *fileStat) isSymlink() bool {
+	// As of https://go.dev/cl/86556, we treat MOUNT_POINT reparse points as
+	// symlinks because otherwise certain directory junction tests in the
+	// path/filepath package would fail.
+	//
+	// However,
+	// https://learn.microsoft.com/en-us/windows/win32/fileio/hard-links-and-junctions
+	// seems to suggest that directory junctions should be treated like hard
+	// links, not symlinks.
+	//
+	// TODO(bcmills): Get more input from Microsoft on what the behavior ought to
+	// be for MOUNT_POINT reparse points.
+
+	return fs.ReparseTag == syscall.IO_REPARSE_TAG_SYMLINK ||
+		fs.ReparseTag == windows.IO_REPARSE_TAG_MOUNT_POINT
+}
+
+func (fs *fileStat) Size() int64 {
+	return int64(fs.FileSizeHigh)<<32 + int64(fs.FileSizeLow)
+}
+
+func (fs *fileStat) Mode() (m FileMode) {
+	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_READONLY != 0 {
+		m |= 0444
+	} else {
+		m |= 0666
+	}
+	if fs.isSymlink() {
+		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 && m&ModeType == 0 {
+		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 = 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 !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 = basename(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
+}