os, syscall: implement Stat and Lstat

File.Stat is left as a stub for now.

Tests are a bit stubbed down because os.ReadDir, os.Symlink, and t.TempDir are not yet (fully) implemented.
TODO: reimport tests from upstream as those materialize.

src/os/export_windows_test.go

@@ -0,0 +1,12 @@
+// 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.
+
+package os
+
+// Export for testing.
+
+var (
+	FixLongPath     = fixLongPath
+	CanUseLongPaths = canUseLongPaths
+)

src/os/file.go

@@ -171,11 +171,6 @@ func (f *File) Stat() (FileInfo, error) {
 	return nil, &PathError{"stat", f.name, ErrNotImplemented}
 }
 
-// Sync is a stub, not yet implemented
-func (f *File) Sync() error {
-	return ErrNotImplemented
-}
-
 func (f *File) SyscallConn() (syscall.RawConn, error) {
 	return nil, ErrNotImplemented
 }
@@ -190,16 +185,6 @@ func (f *File) Truncate(size int64) error {
 	return &PathError{"truncate", f.name, ErrNotImplemented}
 }
 
-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
-}
-
 // PathError records an error and the operation and file path that caused it.
 // TODO: PathError moved to io/fs in go 1.16 and left an alias in os/errors.go.
 // Do the same once we drop support for go 1.15.
@@ -245,16 +230,6 @@ const (
 	O_TRUNC  int = syscall.O_TRUNC
 )
 
-// Stat is a stub, not yet implemented
-func Stat(name string) (FileInfo, error) {
-	return nil, &PathError{"stat", name, ErrNotImplemented}
-}
-
-// Lstat is a stub, not yet implemented
-func Lstat(name string) (FileInfo, error) {
-	return nil, &PathError{"lstat", name, ErrNotImplemented}
-}
-
 func Getwd() (string, error) {
 	return syscall.Getwd()
 }

src/os/file_unix.go

@@ -50,3 +50,19 @@ func (f unixFileHandle) ReadAt(b []byte, offset int64) (n int, err error) {
 	}
 	return
 }
+
+// ignoringEINTR makes a function call and repeats it if it returns an
+// EINTR error. This appears to be required even though we install all
+// signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.
+// Also #20400 and #36644 are issues in which a signal handler is
+// installed without setting SA_RESTART. None of these are the common case,
+// but there are enough of them that it seems that we can't avoid
+// an EINTR loop.
+func ignoringEINTR(fn func() error) error {
+	for {
+		err := fn()
+		if err != syscall.EINTR {
+			return err
+		}
+	}
+}

src/os/file_windows.go

@@ -56,3 +56,21 @@ func tempDir() string {
 func (f unixFileHandle) ReadAt(b []byte, offset int64) (n int, err error) {
 	return -1, ErrNotImplemented
 }
+
+// isWindowsNulName reports whether name is os.DevNull ('NUL') on Windows.
+// True is returned if name is 'NUL' whatever the case.
+func isWindowsNulName(name string) bool {
+	if len(name) != 3 {
+		return false
+	}
+	if name[0] != 'n' && name[0] != 'N' {
+		return false
+	}
+	if name[1] != 'u' && name[1] != 'U' {
+		return false
+	}
+	if name[2] != 'l' && name[2] != 'L' {
+		return false
+	}
+	return true
+}

src/os/path_unix.go

@@ -0,0 +1,35 @@
+// +build darwin linux,!baremetal
+
+// 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 {
+	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
+}

src/os/path_windows.go

@@ -0,0 +1,216 @@
+// 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 accept / 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])
+}

src/os/stat.go

@@ -0,0 +1,21 @@
+// +build !baremetal,!js
+
+// 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)
+}

src/os/stat_darwin.go

@@ -0,0 +1,51 @@
+// 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 = timespecToTime(fs.sys.Mtim)
+	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
+	}
+}
+
+func timespecToTime(ts syscall.Timespec) time.Time {
+	return time.Unix(int64(ts.Sec), int64(ts.Nsec))
+}
+
+// For testing.
+func atime(fi FileInfo) time.Time {
+	return timespecToTime(fi.Sys().(*syscall.Stat_t).Atim)
+}

src/os/stat_linux.go

@@ -0,0 +1,53 @@
+// +build linux,!baremetal
+
+// 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 = timespecToTime(fs.sys.Mtim)
+	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
+	}
+}
+
+func timespecToTime(ts syscall.Timespec) time.Time {
+	return time.Unix(int64(ts.Sec), int64(ts.Nsec))
+}
+
+// For testing.
+func atime(fi FileInfo) time.Time {
+	return timespecToTime(fi.Sys().(*syscall.Stat_t).Atim)
+}

src/os/stat_test.go

@@ -0,0 +1,96 @@
+// Copyright 2018 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_test
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// testStatAndLstat verifies that all os.Stat, os.Lstat os.File.Stat and os.Readdir work.
+func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCheck func(*testing.T, string, fs.FileInfo)) {
+	// TODO: revert to upstream test once fstat and readdir are implemented
+	// test os.Stat
+	sfi, err := os.Stat(path)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	statCheck(t, path, sfi)
+
+	// test os.Lstat
+	lsfi, err := os.Lstat(path)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	lstatCheck(t, path, lsfi)
+
+	if isLink {
+		if os.SameFile(sfi, lsfi) {
+			t.Errorf("stat and lstat of %q should not be the same", path)
+		}
+	} else {
+		if !os.SameFile(sfi, lsfi) {
+			t.Errorf("stat and lstat of %q should be the same", path)
+		}
+	}
+}
+
+// testIsDir verifies that fi refers to directory.
+func testIsDir(t *testing.T, path string, fi fs.FileInfo) {
+	t.Helper()
+	if !fi.IsDir() {
+		t.Errorf("%q should be a directory", path)
+	}
+	if fi.Mode()&fs.ModeSymlink != 0 {
+		t.Errorf("%q should not be a symlink", path)
+	}
+}
+
+// testIsFile verifies that fi refers to file.
+func testIsFile(t *testing.T, path string, fi fs.FileInfo) {
+	t.Helper()
+	if fi.IsDir() {
+		t.Errorf("%q should not be a directory", path)
+	}
+	if fi.Mode()&fs.ModeSymlink != 0 {
+		t.Errorf("%q should not be a symlink", path)
+	}
+}
+
+func testDirStats(t *testing.T, path string) {
+	testStatAndLstat(t, path, false, testIsDir, testIsDir)
+}
+
+func testFileStats(t *testing.T, path string) {
+	testStatAndLstat(t, path, false, testIsFile, testIsFile)
+}
+
+func TestDirAndSymlinkStats(t *testing.T) {
+	// TODO: revert to upstream test once symlinks and t.TempDir are implemented
+	tmpdir := os.TempDir()
+	dir := filepath.Join(tmpdir, "dir")
+	os.Remove(dir)
+	if err := os.Mkdir(dir, 0777); err != nil {
+		t.Fatal(err)
+		return
+	}
+	testDirStats(t, dir)
+
+}
+
+func TestFileAndSymlinkStats(t *testing.T) {
+	// TODO: revert to upstream test once symlinks and t.TempDir are implemented
+	tmpdir := os.TempDir()
+	file := filepath.Join(tmpdir, "file")
+	if err := os.WriteFile(file, []byte("abcdefg"), 0644); err != nil {
+		t.Fatal(err)
+		return
+	}
+	testFileStats(t, file)
+}

src/os/stat_unix.go

@@ -0,0 +1,42 @@
+// +build darwin linux,!baremetal
+
+// 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.
+
+package os
+
+import (
+	"syscall"
+)
+
+// Sync is a stub, not yet implemented
+func (f *File) Sync() error {
+	return ErrNotImplemented
+}
+
+// statNolog stats a file with no test logging.
+func statNolog(name string) (FileInfo, error) {
+	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
+}
+
+// lstatNolog lstats a file with no test logging.
+func lstatNolog(name string) (FileInfo, error) {
+	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
+}

src/os/stat_windows.go

@@ -0,0 +1,89 @@
+// 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"
+	"syscall"
+	"unsafe"
+)
+
+// Sync is a stub, not yet implemented
+func (f *File) Sync() error {
+	return ErrNotImplemented
+}
+
+// stat implements both Stat and Lstat of a file.
+func stat(funcname, name string, createFileAttrs uint32) (FileInfo, error) {
+	if len(name) == 0 {
+		return nil, &PathError{Op: funcname, Path: name, Err: syscall.Errno(syscall.ERROR_PATH_NOT_FOUND)}
+	}
+	if isWindowsNulName(name) {
+		return &devNullStat, nil
+	}
+	namep, err := syscall.UTF16PtrFromString(fixLongPath(name))
+	if err != nil {
+		return nil, &PathError{Op: funcname, Path: name, Err: err}
+	}
+
+	// Try GetFileAttributesEx first, because it is faster than CreateFile.
+	// See https://golang.org/issues/19922#issuecomment-300031421 for details.
+	var fa syscall.Win32FileAttributeData
+	err = syscall.GetFileAttributesEx(namep, syscall.GetFileExInfoStandard, (*byte)(unsafe.Pointer(&fa)))
+	if err == nil && fa.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
+		// Not a symlink.
+		fs := &fileStat{
+			FileAttributes: fa.FileAttributes,
+			CreationTime:   fa.CreationTime,
+			LastAccessTime: fa.LastAccessTime,
+			LastWriteTime:  fa.LastWriteTime,
+			FileSizeHigh:   fa.FileSizeHigh,
+			FileSizeLow:    fa.FileSizeLow,
+		}
+		if err := fs.saveInfoFromPath(name); err != nil {
+			return nil, err
+		}
+		return fs, nil
+	}
+	// GetFileAttributesEx fails with ERROR_SHARING_VIOLATION error for
+	// files, like c:\pagefile.sys. Use FindFirstFile for such files.
+	if err == windows.ERROR_SHARING_VIOLATION {
+		var fd syscall.Win32finddata
+		sh, err := syscall.FindFirstFile(namep, &fd)
+		if err != nil {
+			return nil, &PathError{Op: "FindFirstFile", Path: name, Err: err}
+		}
+		syscall.FindClose(sh)
+		fs := newFileStatFromWin32finddata(&fd)
+		if err := fs.saveInfoFromPath(name); err != nil {
+			return nil, err
+		}
+		return fs, nil
+	}
+
+	// Finally use CreateFile.
+	h, err := syscall.CreateFile(namep, 0, 0, nil,
+		syscall.OPEN_EXISTING, createFileAttrs, 0)
+	if err != nil {
+		return nil, &PathError{Op: "CreateFile", Path: name, Err: err}
+	}
+	defer syscall.CloseHandle(h)
+
+	return newFileStatFromGetFileInformationByHandle(name, h)
+}
+
+// statNolog implements Stat for Windows.
+func statNolog(name string) (FileInfo, error) {
+	return stat("Stat", name, syscall.FILE_FLAG_BACKUP_SEMANTICS)
+}
+
+// lstatNolog implements Lstat for Windows.
+func lstatNolog(name string) (FileInfo, error) {
+	attrs := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS)
+	// Use FILE_FLAG_OPEN_REPARSE_POINT, otherwise CreateFile will follow symlink.
+	// See https://docs.microsoft.com/en-us/windows/desktop/FileIO/symbolic-link-effects-on-file-systems-functions#createfile-and-createfiletransacted
+	attrs |= syscall.FILE_FLAG_OPEN_REPARSE_POINT
+	return stat("Lstat", name, attrs)
+}

src/os/types.go

@@ -0,0 +1,25 @@
+// +build !baremetal,!js
+
+// 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
+
+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
+// of the two underlying structures are identical; on other systems
+// the decision may be based on the path names.
+// 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)
+}

src/os/types_unix.go

@@ -0,0 +1,30 @@
+// +build darwin linux,!baremetal
+
+// 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     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() interface{}   { return &fs.sys }
+
+func sameFile(fs1, fs2 *fileStat) bool {
+	return fs1.sys.Dev == fs2.sys.Dev && fs1.sys.Ino == fs2.sys.Ino
+}

src/os/types_windows.go

@@ -0,0 +1,231 @@
+// 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
+	Reserved0 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,
+		Reserved0:      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 {
+	return &fileStat{
+		FileAttributes: d.FileAttributes,
+		CreationTime:   d.CreationTime,
+		LastAccessTime: d.LastAccessTime,
+		LastWriteTime:  d.LastWriteTime,
+		FileSizeHigh:   d.FileSizeHigh,
+		FileSizeLow:    d.FileSizeLow,
+		Reserved0:      d.Reserved0,
+	}
+}
+
+func (fs *fileStat) isSymlink() bool {
+	// Use instructions described at
+	// https://blogs.msdn.microsoft.com/oldnewthing/20100212-00/?p=14963/
+	// to recognize whether it's a symlink.
+	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
+		return false
+	}
+	return fs.Reserved0 == syscall.IO_REPARSE_TAG_SYMLINK ||
+		fs.Reserved0 == 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 == &devNullStat {
+		return ModeDevice | ModeCharDevice | 0666
+	}
+	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
+	}
+	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() interface{} {
+	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
+	}
+	attrs := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS)
+	if fs.isSymlink() {
+		// Use FILE_FLAG_OPEN_REPARSE_POINT, otherwise CreateFile will follow symlink.
+		// See https://docs.microsoft.com/en-us/windows/desktop/FileIO/symbolic-link-effects-on-file-systems-functions#createfile-and-createfiletransacted
+		attrs |= 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
+}
+
+// devNullStat is fileStat structure describing DevNull file ("NUL").
+var devNullStat = fileStat{
+	name: DevNull,
+	// hopefully this will work for SameFile
+	vol:   0,
+	idxhi: 0,
+	idxlo: 0,
+}
+
+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())
+}

src/syscall/syscall_libc_darwin.go

@@ -2,6 +2,10 @@
 
 package syscall
 
+import (
+	"unsafe"
+)
+
 // This file defines errno and constants to match the darwin libsystem ABI.
 // Values have been copied from src/syscall/zerrors_darwin_amd64.go.
 
@@ -97,3 +101,93 @@ const (
 	MAP_ANON      = 0x1000 // allocated from memory, swap space
 	MAP_ANONYMOUS = MAP_ANON
 )
+
+type Timespec struct {
+	Sec  int64
+	Nsec int64
+}
+
+// Go chose Linux's field names for Stat_t, see https://github.com/golang/go/issues/31735
+type Stat_t struct {
+	Dev       int32
+	Mode      uint16
+	Nlink     uint16
+	Ino       uint64
+	Uid       uint32
+	Gid       uint32
+	Rdev      int32
+	Pad_cgo_0 [4]byte
+	Atim      Timespec
+	Mtim      Timespec
+	Ctim      Timespec
+	Btim      Timespec
+	Size      int64
+	Blocks    int64
+	Blksize   int32
+	Flags     uint32
+	Gen       uint32
+	Lspare    int32
+	Qspare    [2]int64
+}
+
+// Source: https://github.com/apple/darwin-xnu/blob/main/bsd/sys/_types/_s_ifmt.h
+const (
+	S_IEXEC  = 0x40
+	S_IFBLK  = 0x6000
+	S_IFCHR  = 0x2000
+	S_IFDIR  = 0x4000
+	S_IFIFO  = 0x1000
+	S_IFLNK  = 0xa000
+	S_IFMT   = 0xf000
+	S_IFREG  = 0x8000
+	S_IFSOCK = 0xc000
+	S_IFWHT  = 0xe000
+	S_IREAD  = 0x100
+	S_IRGRP  = 0x20
+	S_IROTH  = 0x4
+	S_IRUSR  = 0x100
+	S_IRWXG  = 0x38
+	S_IRWXO  = 0x7
+	S_IRWXU  = 0x1c0
+	S_ISGID  = 0x400
+	S_ISTXT  = 0x200
+	S_ISUID  = 0x800
+	S_ISVTX  = 0x200
+	S_IWGRP  = 0x10
+	S_IWOTH  = 0x2
+	S_IWRITE = 0x80
+	S_IWUSR  = 0x80
+	S_IXGRP  = 0x8
+	S_IXOTH  = 0x1
+	S_IXUSR  = 0x40
+)
+
+func Stat(path string, p *Stat_t) (err error) {
+	data := cstring(path)
+	n := libc_stat(&data[0], unsafe.Pointer(p))
+
+	if n < 0 {
+		err = getErrno()
+	}
+	return
+}
+
+func Lstat(path string, p *Stat_t) (err error) {
+	data := cstring(path)
+	n := libc_lstat(&data[0], unsafe.Pointer(p))
+	if n < 0 {
+		err = getErrno()
+	}
+	return
+}
+
+// The odd $INODE64 suffix is an Apple compatibility feature, see https://assert.cc/posts/darwin_use_64_bit_inode_vs_ctypes/
+// Without it, you get the old, smaller struct stat from mac os 10.2 or so.
+
+// int stat(const char *path, struct stat * buf);
+//export stat$INODE64
+func libc_stat(pathname *byte, ptr unsafe.Pointer) int32
+
+// int lstat(const char *path, struct stat * buf);
+//export lstat$INODE64
+func libc_lstat(pathname *byte, ptr unsafe.Pointer) int32

src/syscall/syscall_libc_wasi.go

@@ -2,6 +2,10 @@
 
 package syscall
 
+import (
+	"unsafe"
+)
+
 // https://github.com/WebAssembly/wasi-libc/blob/main/expected/wasm32-wasi/predefined-macros.txt
 
 type Signal int
@@ -139,3 +143,88 @@ const (
 	EXDEV           Errno = 75 /* Cross-device link */
 	ENOTCAPABLE     Errno = 76 /* Extension: Capabilities insufficient. */
 )
+
+// https://github.com/WebAssembly/wasi-libc/blob/main/libc-bottom-half/headers/public/__struct_timespec.h
+type Timespec struct {
+	Sec  int32
+	Nsec int64
+}
+
+// https://github.com/WebAssembly/wasi-libc/blob/main/libc-bottom-half/headers/public/__struct_stat.h
+// https://github.com/WebAssembly/wasi-libc/blob/main/libc-bottom-half/headers/public/__typedef_ino_t.h
+// etc.
+// Go chose Linux's field names for Stat_t, see https://github.com/golang/go/issues/31735
+type Stat_t struct {
+	Dev       uint64
+	Ino       uint64
+	Nlink     uint64
+	Mode      uint32
+	Uid       uint32
+	Gid       uint32
+	Pad_cgo_0 [4]byte
+	Rdev      uint64
+	Size      int64
+	Blksize   int32
+	Blocks    int64
+
+	Atim   Timespec
+	Mtim   Timespec
+	Ctim   Timespec
+	Qspare [3]int64
+}
+
+// https://github.com/WebAssembly/wasi-libc/blob/main/libc-top-half/musl/include/sys/stat.h
+const (
+	S_IFBLK  = 0x6000
+	S_IFCHR  = 0x2000
+	S_IFDIR  = 0x4000
+	S_IFIFO  = 0x1000
+	S_IFLNK  = 0xa000
+	S_IFMT   = 0xf000
+	S_IFREG  = 0x8000
+	S_IFSOCK = 0xc000
+	S_IREAD  = 0x100
+	S_IRGRP  = 0x20
+	S_IROTH  = 0x4
+	S_IRUSR  = 0x100
+	S_IRWXG  = 0x38
+	S_IRWXO  = 0x7
+	S_IRWXU  = 0x1c0
+	S_ISGID  = 0x400
+	S_ISUID  = 0x800
+	S_ISVTX  = 0x200
+	S_IWGRP  = 0x10
+	S_IWOTH  = 0x2
+	S_IWRITE = 0x80
+	S_IWUSR  = 0x80
+	S_IXGRP  = 0x8
+	S_IXOTH  = 0x1
+	S_IXUSR  = 0x40
+)
+
+func Stat(path string, p *Stat_t) (err error) {
+	data := cstring(path)
+	n := libc_stat(&data[0], unsafe.Pointer(p))
+
+	if n < 0 {
+		err = getErrno()
+	}
+	return
+}
+
+func Lstat(path string, p *Stat_t) (err error) {
+	data := cstring(path)
+	n := libc_lstat(&data[0], unsafe.Pointer(p))
+	if n < 0 {
+		err = getErrno()
+	}
+	return
+}
+
+// int stat(const char *path, struct stat * buf);
+//export stat
+func libc_stat(pathname *byte, ptr unsafe.Pointer) int32
+
+// int lstat(const char *path, struct stat * buf);
+//export lstat
+func libc_lstat(pathname *byte, ptr unsafe.Pointer) int32