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

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // +build aix darwin dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris

 package os

 import (
 	"internal/poll"
 	"internal/syscall/unix"
 	"io"
 	"runtime"
 	"syscall"
 )

 // fixLongPath is a noop on non-Windows platforms.
 func fixLongPath(path string) string {
 	return path
 }

 func rename(oldname, newname string) error {
 	fi, err := Lstat(newname)
 	if err == nil && fi.IsDir() {
 		// There are two independent errors this function can return:
 		// one for a bad oldname, and one for a bad newname.
 		// At this point we've determined the newname is bad.
 		// But just in case oldname is also bad, prioritize returning
 		// the oldname error because that's what we did historically.
 		if _, err := Lstat(oldname); err != nil {
 			if pe, ok := err.(*PathError); ok {
 				err = pe.Err
 			}
 			return &LinkError{"rename", oldname, newname, err}
 		}
 		return &LinkError{"rename", oldname, newname, syscall.EEXIST}
 	}
 	err = syscall.Rename(oldname, newname)
 	if err != nil {
 		return &LinkError{"rename", oldname, newname, err}
 	}
 	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 {
 	pfd         poll.FD
 	name        string
 	dirinfo     *dirInfo // nil unless directory being read
 	nonblock    bool     // whether we set nonblocking mode
 	stdoutOrErr bool     // whether this is stdout or stderr
 	appendMode  bool     // whether file is opened for appending
 }

 // Fd returns the integer Unix file descriptor referencing the open file.
 // The file descriptor is valid only until f.Close is called or f is garbage collected.
 // On Unix systems this will cause the SetDeadline methods to stop working.
 func (f *File) Fd() uintptr {
 	if f == nil {
 		return ^(uintptr(0))
 	}

 	// If we put the file descriptor into nonblocking mode,
 	// then set it to blocking mode before we return it,
 	// because historically we have always returned a descriptor
 	// opened in blocking mode. The File will continue to work,
 	// but any blocking operation will tie up a thread.
 	if f.nonblock {
 		f.pfd.SetBlocking()
 	}

 	return uintptr(f.pfd.Sysfd)
 }

 // 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).
 func NewFile(fd uintptr, name string) *File {
 	kind := kindNewFile
 	if nb, err := unix.IsNonblock(int(fd)); err == nil && nb {
 		kind = kindNonBlock
 	}
 	return newFile(fd, name, kind)
 }

 // newFileKind describes the kind of file to newFile.
 type newFileKind int

 const (
 	kindNewFile newFileKind = iota
 	kindOpenFile
 	kindPipe
 	kindNonBlock
 )

 // newFile is like NewFile, but if called from OpenFile or Pipe
 // (as passed in the kind parameter) it tries to add the file to
 // the runtime poller.
 func newFile(fd uintptr, name string, kind newFileKind) *File {
 	fdi := int(fd)
 	if fdi < 0 {
 		return nil
 	}
 	f := &File{&file{
 		pfd: poll.FD{
 			Sysfd:         fdi,
 			IsStream:      true,
 			ZeroReadIsEOF: true,
 		},
 		name:        name,
 		stdoutOrErr: fdi == 1 || fdi == 2,
 	}}

 	pollable := kind == kindOpenFile || kind == kindPipe || kind == kindNonBlock

 	// If the caller passed a non-blocking filedes (kindNonBlock),
 	// we assume they know what they are doing so we allow it to be
 	// used with kqueue.
 	if kind == kindOpenFile {
 		var st syscall.Stat_t
 		switch runtime.GOOS {
 		case "dragonfly", "freebsd", "netbsd", "openbsd":
 			// Don't try to use kqueue with regular files on *BSDs.
 			// On FreeBSD a regular file is always
 			// reported as ready for writing.
 			// On Dragonfly, NetBSD and OpenBSD the fd is signaled
 			// only once as ready (both read and write).
 			// Issue 19093.
 			if err := syscall.Fstat(fdi, &st); err == nil && st.Mode&syscall.S_IFMT == syscall.S_IFREG {
 				pollable = false
 			}

 		case "darwin":
 			// In addition to the behavior described above for regular files,
 			// on Darwin, kqueue does not work properly with fifos:
 			// closing the last writer does not cause a kqueue event
 			// for any readers. See issue #24164.
 			if err := syscall.Fstat(fdi, &st); err == nil && (st.Mode&syscall.S_IFMT == syscall.S_IFIFO || st.Mode&syscall.S_IFMT == syscall.S_IFREG) {
 				pollable = false
 			}
 		}
 	}

 	if err := f.pfd.Init("file", pollable); err != nil {
 		// An error here indicates a failure to register
 		// with the netpoll system. That can happen for
 		// a file descriptor that is not supported by
 		// epoll/kqueue; for example, disk files on
 		// GNU/Linux systems. We assume that any real error
 		// will show up in later I/O.
 	} else if pollable {
 		// We successfully registered with netpoll, so put
 		// the file into nonblocking mode.
 		if err := syscall.SetNonblock(fdi, true); err == nil {
 			f.nonblock = true
 		}
 	}

 	runtime.SetFinalizer(f.file, (*file).close)
 	return f
 }

 // 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) {
 	if e == syscall.EPIPE && file.stdoutOrErr {
 		sigpipe()
 	}
 }

 // 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) {
 	setSticky := false
 	if !supportsCreateWithStickyBit && flag&O_CREATE != 0 && perm&ModeSticky != 0 {
 		if _, err := Stat(name); IsNotExist(err) {
 			setSticky = true
 		}
 	}

 	var r int
 	for {
 		var e error
 		r, e = syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
 		if e == nil {
 			break
 		}

 		// On OS X, sigaction(2) doesn't guarantee that SA_RESTART will cause
 		// open(2) to be restarted for regular files. This is easy to reproduce on
 		// fuse file systems (see https://golang.org/issue/11180).
 		if runtime.GOOS == "darwin" && e == syscall.EINTR {
 			continue
 		}

 		return nil, &PathError{"open", name, e}
 	}

 	// open(2) itself won't handle the sticky bit on *BSD and Solaris
 	if setSticky {
 		setStickyBit(name)
 	}

 	// There's a race here with fork/exec, which we are
 	// content to live with. See ../syscall/exec_unix.go.
 	if !supportsCloseOnExec {
 		syscall.CloseOnExec(r)
 	}

 	return newFile(uintptr(r), name, kindOpenFile), nil
 }

 // Close closes the File, rendering it unusable for I/O.
 // On files that support SetDeadline, any pending I/O operations will
 // be canceled and return immediately with an error.
 func (f *File) Close() error {
 	if f == nil {
 		return ErrInvalid
 	}
 	return f.file.close()
 }

 func (file *file) close() error {
 	if file == nil {
 		return syscall.EINVAL
 	}
 	if file.dirinfo != nil {
 		file.dirinfo.close()
 	}
 	var err error
 	if e := file.pfd.Close(); e != nil {
 		if e == poll.ErrFileClosing {
 			e = ErrClosed
 		}
 		err = &PathError{"close", file.name, e}
 	}

 	// no need for a finalizer anymore
 	runtime.SetFinalizer(file, nil)
 	return err
 }

 // read reads up to len(b) bytes from the File.
 // It returns the number of bytes read and an error, if any.
 func (f *File) read(b []byte) (n int, err error) {
 	n, err = f.pfd.Read(b)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // pread reads len(b) bytes from the File starting at byte offset off.
 // It returns the number of bytes read and the error, if any.
 // EOF is signaled by a zero count with err set to nil.
 func (f *File) pread(b []byte, off int64) (n int, err error) {
 	n, err = f.pfd.Pread(b, off)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // write writes len(b) bytes to the File.
 // It returns the number of bytes written and an error, if any.
 func (f *File) write(b []byte) (n int, err error) {
 	n, err = f.pfd.Write(b)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // pwrite writes len(b) bytes to the File starting at byte offset off.
 // It returns the number of bytes written and an error, if any.
 func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 	n, err = f.pfd.Pwrite(b, off)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // 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.
 // It returns the new offset and an error, if any.
 func (f *File) seek(offset int64, whence int) (ret int64, err error) {
 	ret, err = f.pfd.Seek(offset, whence)
 	runtime.KeepAlive(f)
 	return ret, err
 }

 // Truncate changes the size of the named file.
 // If the file is a symbolic link, it changes the size of the link's target.
 // If there is an error, it will be of type *PathError.
 func Truncate(name string, size int64) error {
 	if e := syscall.Truncate(name, size); e != nil {
 		return &PathError{"truncate", name, e}
 	}
 	return nil
 }

 // Remove removes the named file or (empty) directory.
 // If there is an error, it will be of type *PathError.
 func Remove(name string) error {
 	// System call interface forces us to know
 	// whether name is a file or directory.
 	// Try both: it is cheaper on average than
 	// doing a Stat plus the right one.
 	e := syscall.Unlink(name)
 	if e == nil {
 		return nil
 	}
 	e1 := syscall.Rmdir(name)
 	if e1 == nil {
 		return nil
 	}

 	// Both failed: figure out which error to return.
 	// OS X and Linux differ on whether unlink(dir)
 	// returns EISDIR, so can't use that. However,
 	// both agree that rmdir(file) returns ENOTDIR,
 	// so we can use that to decide which error is real.
 	// Rmdir might also return ENOTDIR if given a bad
 	// file path, like /etc/passwd/foo, but in that case,
 	// both errors will be ENOTDIR, so it's okay to
 	// use the error from unlink.
 	if e1 != syscall.ENOTDIR {
 		e = e1
 	}
 	return &PathError{"remove", name, e}
 }

 func tempDir() string {
 	dir := Getenv("TMPDIR")
 	if dir == "" {
 		if runtime.GOOS == "android" {
 			dir = "/data/local/tmp"
 		} else {
 			dir = "/tmp"
 		}
 	}
 	return dir
 }

 // Link creates newname as a hard link to the oldname file.
 // If there is an error, it will be of type *LinkError.
 func Link(oldname, newname string) error {
 	e := syscall.Link(oldname, newname)
 	if e != nil {
 		return &LinkError{"link", oldname, newname, e}
 	}
 	return nil
 }

 // Symlink creates newname as a symbolic link to oldname.
 // If there is an error, it will be of type *LinkError.
 func Symlink(oldname, newname string) error {
 	e := syscall.Symlink(oldname, newname)
 	if e != nil {
 		return &LinkError{"symlink", oldname, newname, e}
 	}
 	return nil
 }

 func (f *File) readdir(n int) (fi []FileInfo, err error) {
 	dirname := f.name
 	if dirname == "" {
 		dirname = "."
 	}
 	names, err := f.Readdirnames(n)
 	fi = make([]FileInfo, 0, len(names))
 	for _, filename := range names {
 		fip, lerr := lstat(dirname + "/" + filename)
 		if IsNotExist(lerr) {
 			// File disappeared between readdir + stat.
 			// Just treat it as if it didn't exist.
 			continue
 		}
 		if lerr != nil {
 			return fi, lerr
 		}
 		fi = append(fi, fip)
 	}
 	if len(fi) == 0 && err == nil && n > 0 {
 		// Per File.Readdir, the slice must be non-empty or err
 		// must be non-nil if n > 0.
 		err = io.EOF
 	}
 	return fi, err
 }

 // Readlink returns the destination of the named symbolic link.
 // If there is an error, it will be of type *PathError.
 func Readlink(name string) (string, error) {
 	for len := 128; ; len *= 2 {
 		b := make([]byte, len)
 		n, e := fixCount(syscall.Readlink(name, b))
 		// buffer too small
 		if runtime.GOOS == "aix" && e == syscall.ERANGE {
 			continue
 		}
 		if e != nil {
 			return "", &PathError{"readlink", name, e}
 		}
 		if n < len {
 			return string(b[0:n]), nil
 		}
 	}
 }
	// 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 aix darwin dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris

	package os

	import (
	"internal/poll"
	"internal/syscall/unix"
	"io"
	"runtime"
	"syscall"
	)

	// fixLongPath is a noop on non-Windows platforms.
	func fixLongPath(path string) string {
	return path
	}

	func rename(oldname, newname string) error {
	fi, err := Lstat(newname)
	if err == nil && fi.IsDir() {
	// There are two independent errors this function can return:
	// one for a bad oldname, and one for a bad newname.
	// At this point we've determined the newname is bad.
	// But just in case oldname is also bad, prioritize returning
	// the oldname error because that's what we did historically.
	if _, err := Lstat(oldname); err != nil {
	if pe, ok := err.(*PathError); ok {
	err = pe.Err
	}
	return &LinkError{"rename", oldname, newname, err}
	}
	return &LinkError{"rename", oldname, newname, syscall.EEXIST}
	}
	err = syscall.Rename(oldname, newname)
	if err != nil {
	return &LinkError{"rename", oldname, newname, err}
	}
	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 {
	pfd poll.FD
	name string
	dirinfo *dirInfo // nil unless directory being read
	nonblock bool // whether we set nonblocking mode
	stdoutOrErr bool // whether this is stdout or stderr
	appendMode bool // whether file is opened for appending
	}

	// Fd returns the integer Unix file descriptor referencing the open file.
	// The file descriptor is valid only until f.Close is called or f is garbage collected.
	// On Unix systems this will cause the SetDeadline methods to stop working.
	func (f *File) Fd() uintptr {
	if f == nil {
	return ^(uintptr(0))
	}

	// If we put the file descriptor into nonblocking mode,
	// then set it to blocking mode before we return it,
	// because historically we have always returned a descriptor
	// opened in blocking mode. The File will continue to work,
	// but any blocking operation will tie up a thread.
	if f.nonblock {
	f.pfd.SetBlocking()
	}

	return uintptr(f.pfd.Sysfd)
	}

	// 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).
	func NewFile(fd uintptr, name string) *File {
	kind := kindNewFile
	if nb, err := unix.IsNonblock(int(fd)); err == nil && nb {
	kind = kindNonBlock
	}
	return newFile(fd, name, kind)
	}

	// newFileKind describes the kind of file to newFile.
	type newFileKind int

	const (
	kindNewFile newFileKind = iota
	kindOpenFile
	kindPipe
	kindNonBlock
	)

	// newFile is like NewFile, but if called from OpenFile or Pipe
	// (as passed in the kind parameter) it tries to add the file to
	// the runtime poller.
	func newFile(fd uintptr, name string, kind newFileKind) *File {
	fdi := int(fd)
	if fdi < 0 {
	return nil
	}
	f := &File{&file{
	pfd: poll.FD{
	Sysfd: fdi,
	IsStream: true,
	ZeroReadIsEOF: true,
	},
	name: name,
	stdoutOrErr: fdi == 1 \|\| fdi == 2,
	}}

	pollable := kind == kindOpenFile \|\| kind == kindPipe \|\| kind == kindNonBlock

	// If the caller passed a non-blocking filedes (kindNonBlock),
	// we assume they know what they are doing so we allow it to be
	// used with kqueue.
	if kind == kindOpenFile {
	var st syscall.Stat_t
	switch runtime.GOOS {
	case "dragonfly", "freebsd", "netbsd", "openbsd":
	// Don't try to use kqueue with regular files on *BSDs.
	// On FreeBSD a regular file is always
	// reported as ready for writing.
	// On Dragonfly, NetBSD and OpenBSD the fd is signaled
	// only once as ready (both read and write).
	// Issue 19093.
	if err := syscall.Fstat(fdi, &st); err == nil && st.Mode&syscall.S_IFMT == syscall.S_IFREG {
	pollable = false
	}

	case "darwin":
	// In addition to the behavior described above for regular files,
	// on Darwin, kqueue does not work properly with fifos:
	// closing the last writer does not cause a kqueue event
	// for any readers. See issue #24164.
	if err := syscall.Fstat(fdi, &st); err == nil && (st.Mode&syscall.S_IFMT == syscall.S_IFIFO \|\| st.Mode&syscall.S_IFMT == syscall.S_IFREG) {
	pollable = false
	}
	}
	}

	if err := f.pfd.Init("file", pollable); err != nil {
	// An error here indicates a failure to register
	// with the netpoll system. That can happen for
	// a file descriptor that is not supported by
	// epoll/kqueue; for example, disk files on
	// GNU/Linux systems. We assume that any real error
	// will show up in later I/O.
	} else if pollable {
	// We successfully registered with netpoll, so put
	// the file into nonblocking mode.
	if err := syscall.SetNonblock(fdi, true); err == nil {
	f.nonblock = true
	}
	}

	runtime.SetFinalizer(f.file, (*file).close)
	return f
	}

	// 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) {
	if e == syscall.EPIPE && file.stdoutOrErr {
	sigpipe()
	}
	}

	// 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) {
	setSticky := false
	if !supportsCreateWithStickyBit && flag&O_CREATE != 0 && perm&ModeSticky != 0 {
	if _, err := Stat(name); IsNotExist(err) {
	setSticky = true
	}
	}

	var r int
	for {
	var e error
	r, e = syscall.Open(name, flag\|syscall.O_CLOEXEC, syscallMode(perm))
	if e == nil {
	break
	}

	// On OS X, sigaction(2) doesn't guarantee that SA_RESTART will cause
	// open(2) to be restarted for regular files. This is easy to reproduce on
	// fuse file systems (see https://golang.org/issue/11180).
	if runtime.GOOS == "darwin" && e == syscall.EINTR {
	continue
	}

	return nil, &PathError{"open", name, e}
	}

	// open(2) itself won't handle the sticky bit on *BSD and Solaris
	if setSticky {
	setStickyBit(name)
	}

	// There's a race here with fork/exec, which we are
	// content to live with. See ../syscall/exec_unix.go.
	if !supportsCloseOnExec {
	syscall.CloseOnExec(r)
	}

	return newFile(uintptr(r), name, kindOpenFile), nil
	}

	// Close closes the File, rendering it unusable for I/O.
	// On files that support SetDeadline, any pending I/O operations will
	// be canceled and return immediately with an error.
	func (f *File) Close() error {
	if f == nil {
	return ErrInvalid
	}
	return f.file.close()
	}

	func (file *file) close() error {
	if file == nil {
	return syscall.EINVAL
	}
	if file.dirinfo != nil {
	file.dirinfo.close()
	}
	var err error
	if e := file.pfd.Close(); e != nil {
	if e == poll.ErrFileClosing {
	e = ErrClosed
	}
	err = &PathError{"close", file.name, e}
	}

	// no need for a finalizer anymore
	runtime.SetFinalizer(file, nil)
	return err
	}

	// read reads up to len(b) bytes from the File.
	// It returns the number of bytes read and an error, if any.
	func (f *File) read(b []byte) (n int, err error) {
	n, err = f.pfd.Read(b)
	runtime.KeepAlive(f)
	return n, err
	}

	// pread reads len(b) bytes from the File starting at byte offset off.
	// It returns the number of bytes read and the error, if any.
	// EOF is signaled by a zero count with err set to nil.
	func (f *File) pread(b []byte, off int64) (n int, err error) {
	n, err = f.pfd.Pread(b, off)
	runtime.KeepAlive(f)
	return n, err
	}

	// write writes len(b) bytes to the File.
	// It returns the number of bytes written and an error, if any.
	func (f *File) write(b []byte) (n int, err error) {
	n, err = f.pfd.Write(b)
	runtime.KeepAlive(f)
	return n, err
	}

	// pwrite writes len(b) bytes to the File starting at byte offset off.
	// It returns the number of bytes written and an error, if any.
	func (f *File) pwrite(b []byte, off int64) (n int, err error) {
	n, err = f.pfd.Pwrite(b, off)
	runtime.KeepAlive(f)
	return n, err
	}

	// 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.
	// It returns the new offset and an error, if any.
	func (f *File) seek(offset int64, whence int) (ret int64, err error) {
	ret, err = f.pfd.Seek(offset, whence)
	runtime.KeepAlive(f)
	return ret, err
	}

	// Truncate changes the size of the named file.
	// If the file is a symbolic link, it changes the size of the link's target.
	// If there is an error, it will be of type *PathError.
	func Truncate(name string, size int64) error {
	if e := syscall.Truncate(name, size); e != nil {
	return &PathError{"truncate", name, e}
	}
	return nil
	}

	// Remove removes the named file or (empty) directory.
	// If there is an error, it will be of type *PathError.
	func Remove(name string) error {
	// System call interface forces us to know
	// whether name is a file or directory.
	// Try both: it is cheaper on average than
	// doing a Stat plus the right one.
	e := syscall.Unlink(name)
	if e == nil {
	return nil
	}
	e1 := syscall.Rmdir(name)
	if e1 == nil {
	return nil
	}

	// Both failed: figure out which error to return.
	// OS X and Linux differ on whether unlink(dir)
	// returns EISDIR, so can't use that. However,
	// both agree that rmdir(file) returns ENOTDIR,
	// so we can use that to decide which error is real.
	// Rmdir might also return ENOTDIR if given a bad
	// file path, like /etc/passwd/foo, but in that case,
	// both errors will be ENOTDIR, so it's okay to
	// use the error from unlink.
	if e1 != syscall.ENOTDIR {
	e = e1
	}
	return &PathError{"remove", name, e}
	}

	func tempDir() string {
	dir := Getenv("TMPDIR")
	if dir == "" {
	if runtime.GOOS == "android" {
	dir = "/data/local/tmp"
	} else {
	dir = "/tmp"
	}
	}
	return dir
	}

	// Link creates newname as a hard link to the oldname file.
	// If there is an error, it will be of type *LinkError.
	func Link(oldname, newname string) error {
	e := syscall.Link(oldname, newname)
	if e != nil {
	return &LinkError{"link", oldname, newname, e}
	}
	return nil
	}

	// Symlink creates newname as a symbolic link to oldname.
	// If there is an error, it will be of type *LinkError.
	func Symlink(oldname, newname string) error {
	e := syscall.Symlink(oldname, newname)
	if e != nil {
	return &LinkError{"symlink", oldname, newname, e}
	}
	return nil
	}

	func (f *File) readdir(n int) (fi []FileInfo, err error) {
	dirname := f.name
	if dirname == "" {
	dirname = "."
	}
	names, err := f.Readdirnames(n)
	fi = make([]FileInfo, 0, len(names))
	for _, filename := range names {
	fip, lerr := lstat(dirname + "/" + filename)
	if IsNotExist(lerr) {
	// File disappeared between readdir + stat.
	// Just treat it as if it didn't exist.
	continue
	}
	if lerr != nil {
	return fi, lerr
	}
	fi = append(fi, fip)
	}
	if len(fi) == 0 && err == nil && n > 0 {
	// Per File.Readdir, the slice must be non-empty or err
	// must be non-nil if n > 0.
	err = io.EOF
	}
	return fi, err
	}

	// Readlink returns the destination of the named symbolic link.
	// If there is an error, it will be of type *PathError.
	func Readlink(name string) (string, error) {
	for len := 128; ; len *= 2 {
	b := make([]byte, len)
	n, e := fixCount(syscall.Readlink(name, b))
	// buffer too small
	if runtime.GOOS == "aix" && e == syscall.ERANGE {
	continue
	}
	if e != nil {
	return "", &PathError{"readlink", name, e}
	}
	if n < len {
	return string(b[0:n]), nil
	}
	}
	}