os: implement readdir for darwin and linux

readdir is disabled on linux for 386 and arm until syscall.seek is implemented there.

windows is hard, so leaving that for later.

File src/os/dir_other_go115.go can be deleted when we drop support for go 1.15.

Also adds TestReadNonDir, which was helpful while debugging.

src/os/dir.go

@@ -0,0 +1,127 @@
+// +build go1.16
+
+// 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 (
+	"io/fs"
+	"sort"
+)
+
+type readdirMode int
+
+const (
+	readdirName readdirMode = iota
+	readdirDirEntry
+	readdirFileInfo
+)
+
+// Readdir reads the contents of the directory associated with file and
+// returns a slice of up to n FileInfo values, as would be returned
+// by Lstat, in directory order. Subsequent calls on the same file will yield
+// further FileInfos.
+//
+// If n > 0, Readdir returns at most n FileInfo structures. In this case, if
+// Readdir returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is io.EOF.
+//
+// If n <= 0, Readdir returns all the FileInfo from the directory in
+// a single slice. In this case, if Readdir succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil error. If it encounters an error before the end of the
+// directory, Readdir returns the FileInfo read until that point
+// and a non-nil error.
+//
+// Most clients are better served by the more efficient ReadDir method.
+func (f *File) Readdir(n int) ([]FileInfo, error) {
+	if f == nil {
+		return nil, ErrInvalid
+	}
+	_, _, infos, err := f.readdir(n, readdirFileInfo)
+	if infos == nil {
+		// Readdir has historically always returned a non-nil empty slice, never nil,
+		// even on error (except misuse with nil receiver above).
+		// Keep it that way to avoid breaking overly sensitive callers.
+		infos = []FileInfo{}
+	}
+	return infos, err
+}
+
+// Readdirnames reads the contents of the directory associated with file
+// and returns a slice of up to n names of files in the directory,
+// in directory order. Subsequent calls on the same file will yield
+// further names.
+//
+// If n > 0, Readdirnames returns at most n names. In this case, if
+// Readdirnames returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is io.EOF.
+//
+// If n <= 0, Readdirnames returns all the names from the directory in
+// a single slice. In this case, if Readdirnames succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil error. If it encounters an error before the end of the
+// directory, Readdirnames returns the names read until that point and
+// a non-nil error.
+func (f *File) Readdirnames(n int) (names []string, err error) {
+	if f == nil {
+		return nil, ErrInvalid
+	}
+	names, _, _, err = f.readdir(n, readdirName)
+	if names == nil {
+		// Readdirnames has historically always returned a non-nil empty slice, never nil,
+		// even on error (except misuse with nil receiver above).
+		// Keep it that way to avoid breaking overly sensitive callers.
+		names = []string{}
+	}
+	return names, err
+}
+
+// A DirEntry is an entry read from a directory
+// (using the ReadDir function or a File's ReadDir method).
+type DirEntry = fs.DirEntry
+
+// ReadDir reads the contents of the directory associated with the file f
+// and returns a slice of DirEntry values in directory order.
+// Subsequent calls on the same file will yield later DirEntry records in the directory.
+//
+// If n > 0, ReadDir returns at most n DirEntry records.
+// In this case, if ReadDir returns an empty slice, it will return an error explaining why.
+// At the end of a directory, the error is io.EOF.
+//
+// If n <= 0, ReadDir returns all the DirEntry records remaining in the directory.
+// When it succeeds, it returns a nil error (not io.EOF).
+func (f *File) ReadDir(n int) ([]DirEntry, error) {
+	if f == nil {
+		return nil, ErrInvalid
+	}
+	_, dirents, _, err := f.readdir(n, readdirDirEntry)
+	if dirents == nil {
+		// Match Readdir and Readdirnames: don't return nil slices.
+		dirents = []DirEntry{}
+	}
+	return dirents, err
+}
+
+// testingForceReadDirLstat forces ReadDir to call Lstat, for testing that code path.
+// This can be difficult to provoke on some Unix systems otherwise.
+var testingForceReadDirLstat bool
+
+// ReadDir reads the named directory,
+// returning all its directory entries sorted by filename.
+// If an error occurs reading the directory,
+// ReadDir returns the entries it was able to read before the error,
+// along with the error.
+func ReadDir(name string) ([]DirEntry, error) {
+	f, err := Open(name)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	dirs, err := f.ReadDir(-1)
+	sort.Slice(dirs, func(i, j int) bool { return dirs[i].Name() < dirs[j].Name() })
+	return dirs, err
+}

src/os/dir_darwin.go

@@ -0,0 +1,156 @@
+// 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 (
+	"io"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	dir uintptr // Pointer to DIR structure from dirent.h
+}
+
+func (d *dirInfo) close() {
+	if d.dir == 0 {
+		return
+	}
+	closedir(d.dir)
+	d.dir = 0
+}
+
+func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
+	if f.dirinfo == nil {
+		dir, call, errno := darwinOpenDir(syscallFd(f.handle.(unixFileHandle)))
+		if errno != nil {
+			return nil, nil, nil, &PathError{Op: call, Path: f.name, Err: errno}
+		}
+		f.dirinfo = &dirInfo{
+			dir: dir,
+		}
+	}
+	d := f.dirinfo
+
+	size := n
+	if size <= 0 {
+		size = 100
+		n = -1
+	}
+
+	var dirent syscall.Dirent
+	var entptr *syscall.Dirent
+	for len(names)+len(dirents)+len(infos) < size || n == -1 {
+		if errno := readdir_r(d.dir, &dirent, &entptr); errno != 0 {
+			if errno == syscall.EINTR {
+				continue
+			}
+			return names, dirents, infos, &PathError{Op: "readdir", Path: f.name, Err: errno}
+		}
+		if entptr == nil { // EOF
+			break
+		}
+		if dirent.Ino == 0 {
+			continue
+		}
+		name := (*[len(syscall.Dirent{}.Name)]byte)(unsafe.Pointer(&dirent.Name))[:]
+		for i, c := range name {
+			if c == 0 {
+				name = name[:i]
+				break
+			}
+		}
+		// Check for useless names before allocating a string.
+		if string(name) == "." || string(name) == ".." {
+			continue
+		}
+		if mode == readdirName {
+			names = append(names, string(name))
+		} else if mode == readdirDirEntry {
+			de, err := newUnixDirent(f.name, string(name), dtToType(dirent.Type))
+			if IsNotExist(err) {
+				// File disappeared between readdir and stat.
+				// Treat as if it didn't exist.
+				continue
+			}
+			if err != nil {
+				return nil, dirents, nil, err
+			}
+			dirents = append(dirents, de)
+		} else {
+			info, err := lstat(f.name + "/" + string(name))
+			if IsNotExist(err) {
+				// File disappeared between readdir + stat.
+				// Treat as if it didn't exist.
+				continue
+			}
+			if err != nil {
+				return nil, nil, infos, err
+			}
+			infos = append(infos, info)
+		}
+		runtime.KeepAlive(f)
+	}
+
+	if n > 0 && len(names)+len(dirents)+len(infos) == 0 {
+		return nil, nil, nil, io.EOF
+	}
+	return names, dirents, infos, nil
+}
+
+func dtToType(typ uint8) FileMode {
+	switch typ {
+	case syscall.DT_BLK:
+		return ModeDevice
+	case syscall.DT_CHR:
+		return ModeDevice | ModeCharDevice
+	case syscall.DT_DIR:
+		return ModeDir
+	case syscall.DT_FIFO:
+		return ModeNamedPipe
+	case syscall.DT_LNK:
+		return ModeSymlink
+	case syscall.DT_REG:
+		return 0
+	case syscall.DT_SOCK:
+		return ModeSocket
+	}
+	return ^FileMode(0)
+}
+
+// darwinOpenDir returns a pointer to a DIR structure suitable for
+// ReadDir. In case of an error, the name of the failed
+// syscall is returned along with a syscall.Errno.
+// Borrowed from upstream's internal/poll/fd_opendir_darwin.go
+func darwinOpenDir(fd syscallFd) (uintptr, string, error) {
+	// fdopendir(3) takes control of the file descriptor,
+	// so use a dup.
+	fd2, err := syscall.Dup(fd)
+	if err != nil {
+		return 0, "dup", err
+	}
+	var dir uintptr
+	for {
+		dir, err = syscall.Fdopendir(fd2)
+		if err != syscall.EINTR {
+			break
+		}
+	}
+	if err != nil {
+		syscall.Close(fd2)
+		return 0, "fdopendir", err
+	}
+	return dir, "", nil
+}
+
+// Implemented in syscall/syscall_darwin.go.
+
+//go:linkname closedir syscall.closedir
+func closedir(dir uintptr) (err error)
+
+//go:linkname readdir_r syscall.readdir_r
+func readdir_r(dir uintptr, entry *syscall.Dirent, result **syscall.Dirent) (res syscall.Errno)

src/os/dir_other.go

@@ -0,0 +1,18 @@
+// +build go1.16,baremetal go1.16,js go1.16,wasi go1.16,windows
+
+// 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"
+)
+
+type dirInfo struct {
+}
+
+func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
+	return nil, nil, nil, &PathError{Op: "readdir unimplemented", Err: syscall.ENOTDIR}
+}

src/os/dir_other_go115.go

@@ -0,0 +1,11 @@
+// +build !go1.16
+
+// 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 (f *File) Readdirnames(n int) (names []string, err error) {
+	return nil, ErrInvalid
+}

src/os/dir_test.go

@@ -0,0 +1,181 @@
+// +build darwin linux,!baremetal,!js,!wasi,!386,!arm
+
+package os_test
+
+import (
+	. "os"
+	"testing"
+)
+
+func testReaddirnames(dir string, contents []string, t *testing.T) {
+	file, err := Open(dir)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", dir, err)
+	}
+	defer file.Close()
+	s, err2 := file.Readdirnames(-1)
+	if err2 != nil {
+		t.Fatalf("Readdirnames %q failed: %v", dir, err2)
+	}
+	for _, m := range contents {
+		found := false
+		for _, n := range s {
+			if n == "." || n == ".." {
+				t.Errorf("got %q in directory", n)
+			}
+			if !equal(m, n) {
+				continue
+			}
+			if found {
+				t.Error("present twice:", m)
+			}
+			found = true
+		}
+		if !found {
+			t.Error("could not find", m)
+		}
+	}
+	if s == nil {
+		t.Error("Readdirnames returned nil instead of empty slice")
+	}
+}
+
+func testReaddir(dir string, contents []string, t *testing.T) {
+	file, err := Open(dir)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", dir, err)
+	}
+	defer file.Close()
+	s, err2 := file.Readdir(-1)
+	if err2 != nil {
+		t.Fatalf("Readdir %q failed: %v", dir, err2)
+	}
+	for _, m := range contents {
+		found := false
+		for _, n := range s {
+			if n.Name() == "." || n.Name() == ".." {
+				t.Errorf("got %q in directory", n.Name())
+			}
+			if !equal(m, n.Name()) {
+				continue
+			}
+			if found {
+				t.Error("present twice:", m)
+			}
+			found = true
+		}
+		if !found {
+			t.Error("could not find", m)
+		}
+	}
+	if s == nil {
+		t.Error("Readdir returned nil instead of empty slice")
+	}
+}
+
+func testReadDir(dir string, contents []string, t *testing.T) {
+	file, err := Open(dir)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", dir, err)
+	}
+	defer file.Close()
+	s, err2 := file.ReadDir(-1)
+	if err2 != nil {
+		t.Fatalf("ReadDir %q failed: %v", dir, err2)
+	}
+	for _, m := range contents {
+		found := false
+		for _, n := range s {
+			if n.Name() == "." || n.Name() == ".." {
+				t.Errorf("got %q in directory", n)
+			}
+			if !equal(m, n.Name()) {
+				continue
+			}
+			if found {
+				t.Error("present twice:", m)
+			}
+			found = true
+			lstat, err := Lstat(dir + "/" + m)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if n.IsDir() != lstat.IsDir() {
+				t.Errorf("%s: IsDir=%v, want %v", m, n.IsDir(), lstat.IsDir())
+			}
+			if n.Type() != lstat.Mode().Type() {
+				t.Errorf("%s: IsDir=%v, want %v", m, n.Type(), lstat.Mode().Type())
+			}
+			info, err := n.Info()
+			if err != nil {
+				t.Errorf("%s: Info: %v", m, err)
+				continue
+			}
+			if !SameFile(info, lstat) {
+				t.Errorf("%s: Info: SameFile(info, lstat) = false", m)
+			}
+		}
+		if !found {
+			t.Error("could not find", m)
+		}
+	}
+	if s == nil {
+		t.Error("ReadDir returned nil instead of empty slice")
+	}
+}
+
+func TestFileReaddirnames(t *testing.T) {
+	testReaddirnames(".", dot, t)
+	testReaddirnames(TempDir(), nil, t)
+}
+
+func TestFileReaddir(t *testing.T) {
+	testReaddir(".", dot, t)
+	testReaddir(TempDir(), nil, t)
+}
+
+func TestFileReadDir(t *testing.T) {
+	testReadDir(".", dot, t)
+	testReadDir(TempDir(), nil, t)
+}
+
+func TestReadDir(t *testing.T) {
+	dirname := "rumpelstilzchen"
+	_, err := ReadDir(dirname)
+	if err == nil {
+		t.Fatalf("ReadDir %s: error expected, none found", dirname)
+	}
+
+	dirname = "testdata"
+	list, err := ReadDir(dirname)
+	if err != nil {
+		t.Fatalf("ReadDir %s: %v", dirname, err)
+	}
+
+	foundFile := false
+	foundSubDir := false
+	for _, dir := range list {
+		switch {
+		case !dir.IsDir() && dir.Name() == "hello":
+			foundFile = true
+		case dir.IsDir() && dir.Name() == "issue37161":
+			foundSubDir = true
+		}
+	}
+	if !foundFile {
+		t.Fatalf("ReadDir %s: hello file not found", dirname)
+	}
+	if !foundSubDir {
+		t.Fatalf("ReadDir %s: testdata directory not found", dirname)
+	}
+}
+
+// TestReadNonDir just verifies that opening a non-directory returns an error.
+func TestReadNonDir(t *testing.T) {
+	// Use filename of this source file; it is known to exist, and go tests run in source tree.
+	dirname := "dir_test.go"
+	_, err := ReadDir(dirname)
+	if err == nil {
+		t.Fatalf("ReadDir %s: error on non-dir expected, none found", dirname)
+	}
+}

src/os/dir_unix.go

@@ -0,0 +1,195 @@
+// 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.
+
+// +build linux,!baremetal,!wasi
+
+package os
+
+import (
+	"io"
+	"sync"
+	"syscall"
+	"unsafe"
+)
+
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	buf  *[]byte // buffer for directory I/O
+	nbuf int     // length of buf; return value from Getdirentries
+	bufp int     // location of next record in buf.
+}
+
+const (
+	// More than 5760 to work around https://golang.org/issue/24015.
+	blockSize = 8192
+)
+
+var dirBufPool = sync.Pool{
+	New: func() interface{} {
+		// The buffer must be at least a block long.
+		buf := make([]byte, blockSize)
+		return &buf
+	},
+}
+
+func (d *dirInfo) close() {
+	if d.buf != nil {
+		dirBufPool.Put(d.buf)
+		d.buf = nil
+	}
+}
+
+func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
+	// If this file has no dirinfo, create one.
+	if f.dirinfo == nil {
+		f.dirinfo = new(dirInfo)
+		f.dirinfo.buf = dirBufPool.Get().(*[]byte)
+	}
+	d := f.dirinfo
+
+	// Change the meaning of n for the implementation below.
+	//
+	// The n above was for the public interface of "if n <= 0,
+	// Readdir returns all the FileInfo from the directory in a
+	// single slice".
+	//
+	// But below, we use only negative to mean looping until the
+	// end and positive to mean bounded, with positive
+	// terminating at 0.
+	if n == 0 {
+		n = -1
+	}
+
+	for n != 0 {
+		// Refill the buffer if necessary
+		if d.bufp >= d.nbuf {
+			d.bufp = 0
+			var errno error
+			d.nbuf, errno = syscall.ReadDirent(syscallFd(f.handle.(unixFileHandle)), *d.buf)
+			if d.nbuf < 0 {
+				errno = handleSyscallError(errno)
+			}
+			if errno != nil {
+				return names, dirents, infos, &PathError{Op: "readdirent", Path: f.name, Err: errno}
+			}
+			if d.nbuf <= 0 {
+				break // EOF
+			}
+		}
+
+		// Drain the buffer
+		buf := (*d.buf)[d.bufp:d.nbuf]
+		reclen, ok := direntReclen(buf)
+		if !ok || reclen > uint64(len(buf)) {
+			break
+		}
+		rec := buf[:reclen]
+		d.bufp += int(reclen)
+		ino, ok := direntIno(rec)
+		if !ok {
+			break
+		}
+		if ino == 0 {
+			continue
+		}
+		const namoff = uint64(unsafe.Offsetof(syscall.Dirent{}.Name))
+		namlen, ok := direntNamlen(rec)
+		if !ok || namoff+namlen > uint64(len(rec)) {
+			break
+		}
+		name := rec[namoff : namoff+namlen]
+		for i, c := range name {
+			if c == 0 {
+				name = name[:i]
+				break
+			}
+		}
+		// Check for useless names before allocating a string.
+		if string(name) == "." || string(name) == ".." {
+			continue
+		}
+		if n > 0 { // see 'n == 0' comment above
+			n--
+		}
+		if mode == readdirName {
+			names = append(names, string(name))
+		} else if mode == readdirDirEntry {
+			de, err := newUnixDirent(f.name, string(name), direntType(rec))
+			if IsNotExist(err) {
+				// File disappeared between readdir and stat.
+				// Treat as if it didn't exist.
+				continue
+			}
+			if err != nil {
+				return nil, dirents, nil, err
+			}
+			dirents = append(dirents, de)
+		} else {
+			info, err := lstat(f.name + "/" + string(name))
+			if IsNotExist(err) {
+				// File disappeared between readdir + stat.
+				// Treat as if it didn't exist.
+				continue
+			}
+			if err != nil {
+				return nil, nil, infos, err
+			}
+			infos = append(infos, info)
+		}
+	}
+
+	if n > 0 && len(names)+len(dirents)+len(infos) == 0 {
+		return nil, nil, nil, io.EOF
+	}
+	return names, dirents, infos, nil
+}
+
+// readInt returns the size-bytes unsigned integer in native byte order at offset off.
+func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
+	if len(b) < int(off+size) {
+		return 0, false
+	}
+	if isBigEndian {
+		return readIntBE(b[off:], size), true
+	}
+	return readIntLE(b[off:], size), true
+}
+
+func readIntBE(b []byte, size uintptr) uint64 {
+	switch size {
+	case 1:
+		return uint64(b[0])
+	case 2:
+		_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
+		return uint64(b[1]) | uint64(b[0])<<8
+	case 4:
+		_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+		return uint64(b[3]) | uint64(b[2])<<8 | uint64(b[1])<<16 | uint64(b[0])<<24
+	case 8:
+		_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
+		return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
+			uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
+	default:
+		panic("syscall: readInt with unsupported size")
+	}
+}
+
+func readIntLE(b []byte, size uintptr) uint64 {
+	switch size {
+	case 1:
+		return uint64(b[0])
+	case 2:
+		_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
+		return uint64(b[0]) | uint64(b[1])<<8
+	case 4:
+		_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
+		return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24
+	case 8:
+		_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
+		return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
+			uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
+	default:
+		panic("syscall: readInt with unsupported size")
+	}
+}

src/os/dirent_linux.go

@@ -0,0 +1,53 @@
+// +build !baremetal,!js,!wasi
+
+// Copyright 2020 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"
+	"unsafe"
+)
+
+func direntIno(buf []byte) (uint64, bool) {
+	return readInt(buf, unsafe.Offsetof(syscall.Dirent{}.Ino), unsafe.Sizeof(syscall.Dirent{}.Ino))
+}
+
+func direntReclen(buf []byte) (uint64, bool) {
+	return readInt(buf, unsafe.Offsetof(syscall.Dirent{}.Reclen), unsafe.Sizeof(syscall.Dirent{}.Reclen))
+}
+
+func direntNamlen(buf []byte) (uint64, bool) {
+	reclen, ok := direntReclen(buf)
+	if !ok {
+		return 0, false
+	}
+	return reclen - uint64(unsafe.Offsetof(syscall.Dirent{}.Name)), true
+}
+
+func direntType(buf []byte) FileMode {
+	off := unsafe.Offsetof(syscall.Dirent{}.Type)
+	if off >= uintptr(len(buf)) {
+		return ^FileMode(0) // unknown
+	}
+	typ := buf[off]
+	switch typ {
+	case syscall.DT_BLK:
+		return ModeDevice
+	case syscall.DT_CHR:
+		return ModeDevice | ModeCharDevice
+	case syscall.DT_DIR:
+		return ModeDir
+	case syscall.DT_FIFO:
+		return ModeNamedPipe
+	case syscall.DT_LNK:
+		return ModeSymlink
+	case syscall.DT_REG:
+		return 0
+	case syscall.DT_SOCK:
+		return ModeSocket
+	}
+	return ^FileMode(0) // unknown
+}

src/os/endian_little.go

@@ -0,0 +1,9 @@
+// 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.
+
+// TODO: exclude big endian targets here and include them in endian_big.go, once tinygo supports one
+
+package os
+
+const isBigEndian = false

src/os/file.go

@@ -24,6 +24,9 @@ const (
 	SEEK_END int = io.SeekEnd
 )
 
+// lstat is overridden in tests.
+var lstat = Lstat
+
 // Mkdir creates a directory. If the operation fails, it will return an error of
 // type *PathError.
 func Mkdir(path string, perm FileMode) error {
@@ -66,12 +69,6 @@ func RemoveAll(path string) error {
 	return ErrNotImplemented
 }
 
-// File represents an open file descriptor.
-type File struct {
-	handle FileHandle
-	name   string
-}
-
 // Name returns the name of the file with which it was opened.
 func (f *File) Name() string {
 	return f.name
@@ -88,7 +85,7 @@ func OpenFile(name string, flag int, perm FileMode) (*File, error) {
 	if err != nil {
 		return nil, &PathError{"open", name, err}
 	}
-	return &File{name: name, handle: handle}, nil
+	return NewFile(handle, name), nil
 }
 
 // Open opens the file named for reading.
@@ -170,16 +167,6 @@ func (f *File) Close() (err error) {
 	return
 }
 
-// Readdir is a stub, not yet implemented
-func (f *File) Readdir(n int) ([]FileInfo, error) {
-	return nil, &PathError{"readdir", f.name, ErrNotImplemented}
-}
-
-// Readdirnames is a stub, not yet implemented
-func (f *File) Readdirnames(n int) (names []string, err error) {
-	return nil, &PathError{"readdirnames", f.name, ErrNotImplemented}
-}
-
 // Seek sets the offset for the next Read or Write on file to offset, interpreted
 // according to whence: 0 means relative to the origin of the file, 1 means
 // relative to the current offset, and 2 means relative to the end.

src/os/file_anyos.go

@@ -21,9 +21,9 @@ func init() {
 // Stdin, Stdout, and Stderr are open Files pointing to the standard input,
 // standard output, and standard error file descriptors.
 var (
-	Stdin  = &File{unixFileHandle(syscall.Stdin), "/dev/stdin"}
-	Stdout = &File{unixFileHandle(syscall.Stdout), "/dev/stdout"}
-	Stderr = &File{unixFileHandle(syscall.Stderr), "/dev/stderr"}
+	Stdin  = NewFile(unixFileHandle(syscall.Stdin), "/dev/stdin")
+	Stdout = NewFile(unixFileHandle(syscall.Stdout), "/dev/stdout")
+	Stderr = NewFile(unixFileHandle(syscall.Stderr), "/dev/stderr")
 )
 
 const DevNull = "/dev/null"

src/os/file_go_116.go

@@ -8,19 +8,10 @@ import (
 )
 
 type (
-	DirEntry = fs.DirEntry
 	FileMode = fs.FileMode
 	FileInfo = fs.FileInfo
 )
 
-func (f *File) ReadDir(n int) ([]DirEntry, error) {
-	return nil, &PathError{"ReadDir", f.name, ErrNotImplemented}
-}
-
-func ReadDir(name string) ([]DirEntry, error) {
-	return nil, &PathError{"ReadDir", name, ErrNotImplemented}
-}
-
 // The followings are copied from Go 1.16 official implementation:
 // https://github.com/golang/go/blob/go1.16/src/os/file.go
 

src/os/file_other.go

@@ -9,9 +9,9 @@ import (
 // Stdin, Stdout, and Stderr are open Files pointing to the standard input,
 // standard output, and standard error file descriptors.
 var (
-	Stdin  = &File{stdioFileHandle(0), "/dev/stdin"}
-	Stdout = &File{stdioFileHandle(1), "/dev/stdout"}
-	Stderr = &File{stdioFileHandle(2), "/dev/stderr"}
+	Stdin  = NewFile(stdioFileHandle(0), "/dev/stdin")
+	Stdout = NewFile(stdioFileHandle(1), "/dev/stdout")
+	Stderr = NewFile(stdioFileHandle(2), "/dev/stderr")
 )
 
 // isOS indicates whether we're running on a real operating system with
@@ -22,6 +22,19 @@ const isOS = false
 // number. It implements the FileHandle interface.
 type stdioFileHandle uint8
 
+// file is the real representation of *File.
+// The extra level of indirection ensures that no clients of os
+// can overwrite this data, which could cause the finalizer
+// to close the wrong file descriptor.
+type file struct {
+	handle FileHandle
+	name   string
+}
+
+func NewFile(fd FileHandle, name string) *File {
+	return &File{&file{fd, name}}
+}
+
 // Read is unsupported on this system.
 func (f stdioFileHandle) Read(b []byte) (n int, err error) {
 	return 0, ErrUnsupported

src/os/file_unix.go

@@ -27,20 +27,28 @@ func rename(oldname, newname string) error {
 	return nil
 }
 
+// file is the real representation of *File.
+// The extra level of indirection ensures that no clients of os
+// can overwrite this data, which could cause the finalizer
+// to close the wrong file descriptor.
+type file struct {
+	handle  FileHandle
+	name    string
+	dirinfo *dirInfo // nil unless directory being read
+}
+
+func NewFile(fd FileHandle, name string) *File {
+	return &File{&file{fd, name, nil}}
+}
+
 func Pipe() (r *File, w *File, err error) {
 	var p [2]int
 	err = handleSyscallError(syscall.Pipe2(p[:], syscall.O_CLOEXEC))
 	if err != nil {
 		return
 	}
-	r = &File{
-		handle: unixFileHandle(p[0]),
-		name:   "|0",
-	}
-	w = &File{
-		handle: unixFileHandle(p[1]),
-		name:   "|1",
-	}
+	r = NewFile(unixFileHandle(p[0]), "|0")
+	w = NewFile(unixFileHandle(p[1]), "|1")
 	return
 }
 
@@ -108,3 +116,41 @@ func (f unixFileHandle) Seek(offset int64, whence int) (int64, error) {
 	newoffset, err := syscall.Seek(syscallFd(f), offset, whence)
 	return newoffset, handleSyscallError(err)
 }
+
+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) {
+	if d.info != nil {
+		return d.info, nil
+	}
+	return lstat(d.parent + "/" + d.name)
+}
+
+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
+}

src/os/file_windows.go

@@ -33,20 +33,29 @@ func rename(oldname, newname string) error {
 	return nil
 }
 
+type file struct {
+	handle FileHandle
+	name   string
+}
+
+func NewFile(fd FileHandle, name string) *File {
+	return &File{&file{fd, name}}
+}
+
 func Pipe() (r *File, w *File, err error) {
 	var p [2]syscall.Handle
 	e := handleSyscallError(syscall.Pipe(p[:]))
 	if e != nil {
 		return nil, nil, err
 	}
-	r = &File{
-		handle: unixFileHandle(p[0]),
-		name:   "|0",
-	}
-	w = &File{
-		handle: unixFileHandle(p[1]),
-		name:   "|1",
-	}
+	r = NewFile(
+		unixFileHandle(p[0]),
+		"|0",
+	)
+	w = NewFile(
+		unixFileHandle(p[1]),
+		"|1",
+	)
 	return
 }
 

src/os/os_anyos_test.go

@@ -13,6 +13,17 @@ import (
 	"time"
 )
 
+var dot = []string{
+	"dir.go",
+	"env.go",
+	"errors.go",
+	"file.go",
+	"os_test.go",
+	"types.go",
+	"stat_darwin.go",
+	"stat_linux.go",
+}
+
 func randomName() string {
 	// fastrand() does not seem available here, so fake it
 	ns := time.Now().Nanosecond()

src/os/types.go

@@ -1,25 +1,10 @@
-// +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)
+// File represents an open file descriptor.
+type File struct {
+	*file // os specific
 }

src/os/types_anyos.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/syscall/syscall_libc.go

@@ -19,6 +19,14 @@ func Close(fd int) (err error) {
 	return
 }
 
+func Dup(fd int) (fd2 int, err error) {
+	fd2 = int(libc_dup(int32(fd)))
+	if fd2 < 0 {
+		err = getErrno()
+	}
+	return
+}
+
 func Write(fd int, p []byte) (n int, err error) {
 	buf, count := splitSlice(p)
 	n = libc_write(int32(fd), buf, uint(count))
@@ -297,6 +305,10 @@ func libc_open(pathname *byte, flags int32, mode uint32) int32
 //export close
 func libc_close(fd int32) int32
 
+// int dup(int fd)
+//export dup
+func libc_dup(fd int32) int32
+
 // void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
 //export mmap
 func libc_mmap(addr unsafe.Pointer, length uintptr, prot, flags, fd int32, offset uintptr) unsafe.Pointer

src/syscall/syscall_libc_darwin.go

@@ -40,6 +40,19 @@ func (e Errno) Is(target error) bool {
 	return false
 }
 
+// Source: upstream zerrors_darwin_amd64.go
+const (
+	DT_BLK     = 0x6
+	DT_CHR     = 0x2
+	DT_DIR     = 0x4
+	DT_FIFO    = 0x1
+	DT_LNK     = 0xa
+	DT_REG     = 0x8
+	DT_SOCK    = 0xc
+	DT_UNKNOWN = 0x0
+	DT_WHT     = 0xe
+)
+
 // Source: https://opensource.apple.com/source/xnu/xnu-7195.81.3/bsd/sys/errno.h.auto.html
 const (
 	EPERM       Errno = 1
@@ -107,6 +120,17 @@ type Timespec struct {
 	Nsec int64
 }
 
+// Source: upstream ztypes_darwin_amd64.go
+type Dirent struct {
+	Ino       uint64
+	Seekoff   uint64
+	Reclen    uint16
+	Namlen    uint16
+	Type      uint8
+	Name      [1024]int8
+	Pad_cgo_0 [3]byte
+}
+
 // Go chose Linux's field names for Stat_t, see https://github.com/golang/go/issues/31735
 type Stat_t struct {
 	Dev       int32
@@ -190,9 +214,36 @@ func Lstat(path string, p *Stat_t) (err error) {
 	return
 }
 
-// The odd $INODE64 suffix is an Apple compatibility feature, see https://assert.cc/posts/darwin_use_64_bit_inode_vs_ctypes/
+func Fdopendir(fd int) (dir uintptr, err error) {
+	r0 := libc_fdopendir(int32(fd))
+	dir = uintptr(r0)
+	if dir == 0 {
+		err = getErrno()
+	}
+	return
+}
+
+func readdir_r(dir uintptr, entry *Dirent, result **Dirent) (err error) {
+	e1 := libc_readdir_r(unsafe.Pointer(dir), unsafe.Pointer(entry), unsafe.Pointer(result))
+	if e1 != 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/
+// and https://github.com/golang/go/issues/35269
 // Without it, you get the old, smaller struct stat from mac os 10.2 or so.
 
+// struct DIR * buf fdopendir(int fd);
+//export fdopendir$INODE64
+func libc_fdopendir(fd int32) unsafe.Pointer
+
+// int readdir_r(struct DIR * buf, struct dirent *entry, struct dirent **result);
+//export readdir_r$INODE64
+func libc_readdir_r(unsafe.Pointer, unsafe.Pointer, unsafe.Pointer) int32
+
 // int stat(const char *path, struct stat * buf);
 //export stat$INODE64
 func libc_stat(pathname *byte, ptr unsafe.Pointer) int32

src/syscall/syscall_libc_wasi.go

@@ -202,6 +202,31 @@ const (
 	S_IXUSR  = 0x40
 )
 
+// dummy
+const (
+	DT_BLK     = 0x6
+	DT_CHR     = 0x2
+	DT_DIR     = 0x4
+	DT_FIFO    = 0x1
+	DT_LNK     = 0xa
+	DT_REG     = 0x8
+	DT_SOCK    = 0xc
+	DT_UNKNOWN = 0x0
+	DT_WHT     = 0xe
+)
+
+// dummy
+type Dirent struct {
+	Ino    uint64
+	Reclen uint16
+	Type   uint8
+	Name   [1024]int8
+}
+
+func ReadDirent(fd int, buf []byte) (n int, err error) {
+	return -1, ENOSYS
+}
+
 func Stat(path string, p *Stat_t) (err error) {
 	data := cstring(path)
 	n := libc_stat(&data[0], unsafe.Pointer(p))