src/os/file_plan9.go - go.git - Git at Google

 // 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

 import (
 	"internal/bytealg"
 	"internal/poll"
 	"io"
 	"runtime"
 	"sync"
 	"sync/atomic"
 	"syscall"
 	"time"
 )

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

 // 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 {
 	fdmu       poll.FDMutex
 	fd         int
 	name       string
 	dirinfo    atomic.Pointer[dirInfo] // nil unless directory being read
 	appendMode bool                    // whether file is opened for appending
 }

 // Fd returns the integer Plan 9 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 [File.SetDeadline]
 // methods to stop working.
 //
 // As an alternative, see the f.SyscallConn method.
 func (f *File) Fd() uintptr {
 	if f == nil {
 		return ^(uintptr(0))
 	}
 	return uintptr(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.
 func NewFile(fd uintptr, name string) *File {
 	fdi := int(fd)
 	if fdi < 0 {
 		return nil
 	}
 	f := &File{&file{fd: fdi, name: name}}
 	runtime.SetFinalizer(f.file, (*file).close)
 	return f
 }

 // Auxiliary information if the File describes a directory
 type dirInfo struct {
 	mu   sync.Mutex
 	buf  [syscall.STATMAX]byte // buffer for directory I/O
 	nbuf int                   // length of buf; return value from Read
 	bufp int                   // location of next record in buf.
 }

 func epipecheck(file *File, e error) {
 }

 // 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"

 // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
 func syscallMode(i FileMode) (o uint32) {
 	o |= uint32(i.Perm())
 	if i&ModeAppend != 0 {
 		o |= syscall.DMAPPEND
 	}
 	if i&ModeExclusive != 0 {
 		o |= syscall.DMEXCL
 	}
 	if i&ModeTemporary != 0 {
 		o |= syscall.DMTMP
 	}
 	return
 }

 // openFileNolog is the Plan 9 implementation of OpenFile.
 func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
 	var (
 		fd     int
 		e      error
 		create bool
 		excl   bool
 		trunc  bool
 		append bool
 	)

 	if flag&O_CREATE == O_CREATE {
 		flag = flag & ^O_CREATE
 		create = true
 	}
 	if flag&O_EXCL == O_EXCL {
 		excl = true
 	}
 	if flag&O_TRUNC == O_TRUNC {
 		trunc = true
 	}
 	// O_APPEND is emulated on Plan 9
 	if flag&O_APPEND == O_APPEND {
 		flag = flag &^ O_APPEND
 		append = true
 	}

 	if (create && trunc) || excl {
 		fd, e = syscall.Create(name, flag, syscallMode(perm))
 	} else {
 		fd, e = syscall.Open(name, flag)
 		if IsNotExist(e) && create {
 			fd, e = syscall.Create(name, flag, syscallMode(perm))
 			if e != nil {
 				return nil, &PathError{Op: "create", Path: name, Err: e}
 			}
 		}
 	}

 	if e != nil {
 		return nil, &PathError{Op: "open", Path: name, Err: e}
 	}

 	if append {
 		if _, e = syscall.Seek(fd, 0, io.SeekEnd); e != nil {
 			return nil, &PathError{Op: "seek", Path: name, Err: e}
 		}
 	}

 	return NewFile(uintptr(fd), name), nil
 }

 func openDirNolog(name string) (*File, error) {
 	return openFileNolog(name, O_RDONLY, 0)
 }

 // 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 ErrClosed error.
 // Close will return an error if it has already been called.
 func (f *File) Close() error {
 	if f == nil {
 		return ErrInvalid
 	}
 	return f.file.close()
 }

 func (file *file) close() error {
 	if !file.fdmu.IncrefAndClose() {
 		return &PathError{Op: "close", Path: file.name, Err: ErrClosed}
 	}

 	// At this point we should cancel any pending I/O.
 	// How do we do that on Plan 9?

 	err := file.decref()

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

 // destroy actually closes the descriptor. This is called when
 // there are no remaining references, by the decref, readUnlock,
 // and writeUnlock methods.
 func (file *file) destroy() error {
 	var err error
 	if e := syscall.Close(file.fd); e != nil {
 		err = &PathError{Op: "close", Path: file.name, Err: e}
 	}
 	return err
 }

 // Stat returns the FileInfo structure describing file.
 // If there is an error, it will be of type *PathError.
 func (f *File) Stat() (FileInfo, error) {
 	if f == nil {
 		return nil, ErrInvalid
 	}
 	d, err := dirstat(f)
 	if err != nil {
 		return nil, err
 	}
 	return fileInfoFromStat(d), nil
 }

 // Truncate changes the size of the file.
 // It does not change the I/O offset.
 // If there is an error, it will be of type *PathError.
 func (f *File) Truncate(size int64) error {
 	if f == nil {
 		return ErrInvalid
 	}

 	var d syscall.Dir
 	d.Null()
 	d.Length = size

 	var buf [syscall.STATFIXLEN]byte
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &PathError{Op: "truncate", Path: f.name, Err: err}
 	}

 	if err := f.incref("truncate"); err != nil {
 		return err
 	}
 	defer f.decref()

 	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
 		return &PathError{Op: "truncate", Path: f.name, Err: err}
 	}
 	return nil
 }

 const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)

 func (f *File) chmod(mode FileMode) error {
 	if f == nil {
 		return ErrInvalid
 	}
 	var d syscall.Dir

 	odir, e := dirstat(f)
 	if e != nil {
 		return &PathError{Op: "chmod", Path: f.name, Err: e}
 	}
 	d.Null()
 	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask

 	var buf [syscall.STATFIXLEN]byte
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &PathError{Op: "chmod", Path: f.name, Err: err}
 	}

 	if err := f.incref("chmod"); err != nil {
 		return err
 	}
 	defer f.decref()

 	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
 		return &PathError{Op: "chmod", Path: f.name, Err: err}
 	}
 	return nil
 }

 // Sync commits the current contents of the file to stable storage.
 // Typically, this means flushing the file system's in-memory copy
 // of recently written data to disk.
 func (f *File) Sync() error {
 	if f == nil {
 		return ErrInvalid
 	}
 	var d syscall.Dir
 	d.Null()

 	var buf [syscall.STATFIXLEN]byte
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &PathError{Op: "sync", Path: f.name, Err: err}
 	}

 	if err := f.incref("sync"); err != nil {
 		return err
 	}
 	defer f.decref()

 	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
 		return &PathError{Op: "sync", Path: f.name, Err: err}
 	}
 	return nil
 }

 // 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) {
 	if err := f.readLock(); err != nil {
 		return 0, err
 	}
 	defer f.readUnlock()
 	n, e := fixCount(syscall.Read(f.fd, b))
 	if n == 0 && len(b) > 0 && e == nil {
 		return 0, io.EOF
 	}
 	return n, e
 }

 // 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) {
 	if err := f.readLock(); err != nil {
 		return 0, err
 	}
 	defer f.readUnlock()
 	n, e := fixCount(syscall.Pread(f.fd, b, off))
 	if n == 0 && len(b) > 0 && e == nil {
 		return 0, io.EOF
 	}
 	return n, e
 }

 // write writes len(b) bytes to the File.
 // It returns the number of bytes written and an error, if any.
 // Since Plan 9 preserves message boundaries, never allow
 // a zero-byte write.
 func (f *File) write(b []byte) (n int, err error) {
 	if err := f.writeLock(); err != nil {
 		return 0, err
 	}
 	defer f.writeUnlock()
 	if len(b) == 0 {
 		return 0, nil
 	}
 	return fixCount(syscall.Write(f.fd, b))
 }

 // 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.
 // Since Plan 9 preserves message boundaries, never allow
 // a zero-byte write.
 func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 	if err := f.writeLock(); err != nil {
 		return 0, err
 	}
 	defer f.writeUnlock()
 	if len(b) == 0 {
 		return 0, nil
 	}
 	return fixCount(syscall.Pwrite(f.fd, b, off))
 }

 // 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) {
 	if err := f.incref(""); err != nil {
 		return 0, err
 	}
 	defer f.decref()
 	// Free cached dirinfo, so we allocate a new one if we
 	// access this file as a directory again. See #35767 and #37161.
 	f.dirinfo.Store(nil)
 	return syscall.Seek(f.fd, offset, whence)
 }

 // 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 {
 	var d syscall.Dir

 	d.Null()
 	d.Length = size

 	var buf [syscall.STATFIXLEN]byte
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &PathError{Op: "truncate", Path: name, Err: err}
 	}
 	if err = syscall.Wstat(name, buf[:n]); err != nil {
 		return &PathError{Op: "truncate", Path: name, Err: err}
 	}
 	return nil
 }

 // Remove removes the named file or directory.
 // If there is an error, it will be of type *PathError.
 func Remove(name string) error {
 	if e := syscall.Remove(name); e != nil {
 		return &PathError{Op: "remove", Path: name, Err: e}
 	}
 	return nil
 }

 // hasPrefix from the strings package.
 func hasPrefix(s, prefix string) bool {
 	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
 }

 func rename(oldname, newname string) error {
 	dirname := oldname[:bytealg.LastIndexByteString(oldname, '/')+1]
 	if hasPrefix(newname, dirname) {
 		newname = newname[len(dirname):]
 	} else {
 		return &LinkError{"rename", oldname, newname, ErrInvalid}
 	}

 	// If newname still contains slashes after removing the oldname
 	// prefix, the rename is cross-directory and must be rejected.
 	if bytealg.LastIndexByteString(newname, '/') >= 0 {
 		return &LinkError{"rename", oldname, newname, ErrInvalid}
 	}

 	var d syscall.Dir

 	d.Null()
 	d.Name = newname

 	buf := make([]byte, syscall.STATFIXLEN+len(d.Name))
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &LinkError{"rename", oldname, newname, err}
 	}

 	// If newname already exists and is not a directory, rename replaces it.
 	f, err := Stat(dirname + newname)
 	if err == nil && !f.IsDir() {
 		Remove(dirname + newname)
 	}

 	if err = syscall.Wstat(oldname, buf[:n]); err != nil {
 		return &LinkError{"rename", oldname, newname, err}
 	}
 	return nil
 }

 // See docs in file.go:Chmod.
 func chmod(name string, mode FileMode) error {
 	var d syscall.Dir

 	odir, e := dirstat(name)
 	if e != nil {
 		return &PathError{Op: "chmod", Path: name, Err: e}
 	}
 	d.Null()
 	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask

 	var buf [syscall.STATFIXLEN]byte
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &PathError{Op: "chmod", Path: name, Err: err}
 	}
 	if err = syscall.Wstat(name, buf[:n]); err != nil {
 		return &PathError{Op: "chmod", Path: name, Err: err}
 	}
 	return nil
 }

 // Chtimes changes the access and modification times of the named
 // file, similar to the Unix utime() or utimes() functions.
 // A zero time.Time value will leave the corresponding file time unchanged.
 //
 // The underlying filesystem may truncate or round the values to a
 // less precise time unit.
 // If there is an error, it will be of type *PathError.
 func Chtimes(name string, atime time.Time, mtime time.Time) error {
 	var d syscall.Dir

 	d.Null()
 	d.Atime = uint32(atime.Unix())
 	d.Mtime = uint32(mtime.Unix())
 	if atime.IsZero() {
 		d.Atime = 0xFFFFFFFF
 	}
 	if mtime.IsZero() {
 		d.Mtime = 0xFFFFFFFF
 	}

 	var buf [syscall.STATFIXLEN]byte
 	n, err := d.Marshal(buf[:])
 	if err != nil {
 		return &PathError{Op: "chtimes", Path: name, Err: err}
 	}
 	if err = syscall.Wstat(name, buf[:n]); err != nil {
 		return &PathError{Op: "chtimes", Path: name, Err: err}
 	}
 	return nil
 }

 // Pipe returns a connected pair of Files; reads from r return bytes
 // written to w. It returns the files and an error, if any.
 func Pipe() (r *File, w *File, err error) {
 	var p [2]int

 	if e := syscall.Pipe(p[0:]); e != nil {
 		return nil, nil, NewSyscallError("pipe", e)
 	}

 	return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil
 }

 // not supported on Plan 9

 // 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 {
 	return &LinkError{"link", oldname, newname, syscall.EPLAN9}
 }

 // Symlink creates newname as a symbolic link to oldname.
 // On Windows, a symlink to a non-existent oldname creates a file symlink;
 // if oldname is later created as a directory the symlink will not work.
 // If there is an error, it will be of type *LinkError.
 func Symlink(oldname, newname string) error {
 	return &LinkError{"symlink", oldname, newname, syscall.EPLAN9}
 }

 func readlink(name string) (string, error) {
 	return "", &PathError{Op: "readlink", Path: name, Err: syscall.EPLAN9}
 }

 // Chown changes the numeric uid and gid of the named file.
 // If the file is a symbolic link, it changes the uid and gid of the link's target.
 // A uid or gid of -1 means to not change that value.
 // If there is an error, it will be of type *PathError.
 //
 // On Windows or Plan 9, Chown always returns the syscall.EWINDOWS or
 // EPLAN9 error, wrapped in *PathError.
 func Chown(name string, uid, gid int) error {
 	return &PathError{Op: "chown", Path: name, Err: syscall.EPLAN9}
 }

 // Lchown changes the numeric uid and gid of the named file.
 // If the file is a symbolic link, it changes the uid and gid of the link itself.
 // If there is an error, it will be of type *PathError.
 func Lchown(name string, uid, gid int) error {
 	return &PathError{Op: "lchown", Path: name, Err: syscall.EPLAN9}
 }

 // Chown changes the numeric uid and gid of the named file.
 // If there is an error, it will be of type *PathError.
 func (f *File) Chown(uid, gid int) error {
 	if f == nil {
 		return ErrInvalid
 	}
 	return &PathError{Op: "chown", Path: f.name, Err: syscall.EPLAN9}
 }

 func tempDir() string {
 	dir := Getenv("TMPDIR")
 	if dir == "" {
 		dir = "/tmp"
 	}
 	return dir
 }

 // Chdir changes the current working directory to the file,
 // which must be a directory.
 // If there is an error, it will be of type *PathError.
 func (f *File) Chdir() error {
 	if err := f.incref("chdir"); err != nil {
 		return err
 	}
 	defer f.decref()
 	if e := syscall.Fchdir(f.fd); e != nil {
 		return &PathError{Op: "chdir", Path: f.name, Err: e}
 	}
 	return nil
 }

 // setDeadline sets the read and write deadline.
 func (f *File) setDeadline(time.Time) error {
 	if err := f.checkValid("SetDeadline"); err != nil {
 		return err
 	}
 	return poll.ErrNoDeadline
 }

 // setReadDeadline sets the read deadline.
 func (f *File) setReadDeadline(time.Time) error {
 	if err := f.checkValid("SetReadDeadline"); err != nil {
 		return err
 	}
 	return poll.ErrNoDeadline
 }

 // setWriteDeadline sets the write deadline.
 func (f *File) setWriteDeadline(time.Time) error {
 	if err := f.checkValid("SetWriteDeadline"); err != nil {
 		return err
 	}
 	return poll.ErrNoDeadline
 }

 // checkValid checks whether f is valid for use, but does not prepare
 // to actually use it. If f is not ready checkValid returns an appropriate
 // error, perhaps incorporating the operation name op.
 func (f *File) checkValid(op string) error {
 	if f == nil {
 		return ErrInvalid
 	}
 	if err := f.incref(op); err != nil {
 		return err
 	}
 	return f.decref()
 }

 type rawConn struct{}

 func (c *rawConn) Control(f func(uintptr)) error {
 	return syscall.EPLAN9
 }

 func (c *rawConn) Read(f func(uintptr) bool) error {
 	return syscall.EPLAN9
 }

 func (c *rawConn) Write(f func(uintptr) bool) error {
 	return syscall.EPLAN9
 }

 func newRawConn(file *File) (*rawConn, error) {
 	return nil, syscall.EPLAN9
 }

 func ignoringEINTR(fn func() error) error {
 	return fn()
 }
	// 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

	import (
	"internal/bytealg"
	"internal/poll"
	"io"
	"runtime"
	"sync"
	"sync/atomic"
	"syscall"
	"time"
	)

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

	// 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 {
	fdmu poll.FDMutex
	fd int
	name string
	dirinfo atomic.Pointer[dirInfo] // nil unless directory being read
	appendMode bool // whether file is opened for appending
	}

	// Fd returns the integer Plan 9 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 [File.SetDeadline]
	// methods to stop working.
	//
	// As an alternative, see the f.SyscallConn method.
	func (f *File) Fd() uintptr {
	if f == nil {
	return ^(uintptr(0))
	}
	return uintptr(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.
	func NewFile(fd uintptr, name string) *File {
	fdi := int(fd)
	if fdi < 0 {
	return nil
	}
	f := &File{&file{fd: fdi, name: name}}
	runtime.SetFinalizer(f.file, (*file).close)
	return f
	}

	// Auxiliary information if the File describes a directory
	type dirInfo struct {
	mu sync.Mutex
	buf [syscall.STATMAX]byte // buffer for directory I/O
	nbuf int // length of buf; return value from Read
	bufp int // location of next record in buf.
	}

	func epipecheck(file *File, e error) {
	}

	// 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"

	// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
	func syscallMode(i FileMode) (o uint32) {
	o \|= uint32(i.Perm())
	if i&ModeAppend != 0 {
	o \|= syscall.DMAPPEND
	}
	if i&ModeExclusive != 0 {
	o \|= syscall.DMEXCL
	}
	if i&ModeTemporary != 0 {
	o \|= syscall.DMTMP
	}
	return
	}

	// openFileNolog is the Plan 9 implementation of OpenFile.
	func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
	var (
	fd int
	e error
	create bool
	excl bool
	trunc bool
	append bool
	)

	if flag&O_CREATE == O_CREATE {
	flag = flag & ^O_CREATE
	create = true
	}
	if flag&O_EXCL == O_EXCL {
	excl = true
	}
	if flag&O_TRUNC == O_TRUNC {
	trunc = true
	}
	// O_APPEND is emulated on Plan 9
	if flag&O_APPEND == O_APPEND {
	flag = flag &^ O_APPEND
	append = true
	}

	if (create && trunc) \|\| excl {
	fd, e = syscall.Create(name, flag, syscallMode(perm))
	} else {
	fd, e = syscall.Open(name, flag)
	if IsNotExist(e) && create {
	fd, e = syscall.Create(name, flag, syscallMode(perm))
	if e != nil {
	return nil, &PathError{Op: "create", Path: name, Err: e}
	}
	}
	}

	if e != nil {
	return nil, &PathError{Op: "open", Path: name, Err: e}
	}

	if append {
	if _, e = syscall.Seek(fd, 0, io.SeekEnd); e != nil {
	return nil, &PathError{Op: "seek", Path: name, Err: e}
	}
	}

	return NewFile(uintptr(fd), name), nil
	}

	func openDirNolog(name string) (*File, error) {
	return openFileNolog(name, O_RDONLY, 0)
	}

	// 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 ErrClosed error.
	// Close will return an error if it has already been called.
	func (f *File) Close() error {
	if f == nil {
	return ErrInvalid
	}
	return f.file.close()
	}

	func (file *file) close() error {
	if !file.fdmu.IncrefAndClose() {
	return &PathError{Op: "close", Path: file.name, Err: ErrClosed}
	}

	// At this point we should cancel any pending I/O.
	// How do we do that on Plan 9?

	err := file.decref()

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

	// destroy actually closes the descriptor. This is called when
	// there are no remaining references, by the decref, readUnlock,
	// and writeUnlock methods.
	func (file *file) destroy() error {
	var err error
	if e := syscall.Close(file.fd); e != nil {
	err = &PathError{Op: "close", Path: file.name, Err: e}
	}
	return err
	}

	// Stat returns the FileInfo structure describing file.
	// If there is an error, it will be of type *PathError.
	func (f *File) Stat() (FileInfo, error) {
	if f == nil {
	return nil, ErrInvalid
	}
	d, err := dirstat(f)
	if err != nil {
	return nil, err
	}
	return fileInfoFromStat(d), nil
	}

	// Truncate changes the size of the file.
	// It does not change the I/O offset.
	// If there is an error, it will be of type *PathError.
	func (f *File) Truncate(size int64) error {
	if f == nil {
	return ErrInvalid
	}

	var d syscall.Dir
	d.Null()
	d.Length = size

	var buf [syscall.STATFIXLEN]byte
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &PathError{Op: "truncate", Path: f.name, Err: err}
	}

	if err := f.incref("truncate"); err != nil {
	return err
	}
	defer f.decref()

	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
	return &PathError{Op: "truncate", Path: f.name, Err: err}
	}
	return nil
	}

	const chmodMask = uint32(syscall.DMAPPEND \| syscall.DMEXCL \| syscall.DMTMP \| ModePerm)

	func (f *File) chmod(mode FileMode) error {
	if f == nil {
	return ErrInvalid
	}
	var d syscall.Dir

	odir, e := dirstat(f)
	if e != nil {
	return &PathError{Op: "chmod", Path: f.name, Err: e}
	}
	d.Null()
	d.Mode = odir.Mode&^chmodMask \| syscallMode(mode)&chmodMask

	var buf [syscall.STATFIXLEN]byte
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &PathError{Op: "chmod", Path: f.name, Err: err}
	}

	if err := f.incref("chmod"); err != nil {
	return err
	}
	defer f.decref()

	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
	return &PathError{Op: "chmod", Path: f.name, Err: err}
	}
	return nil
	}

	// Sync commits the current contents of the file to stable storage.
	// Typically, this means flushing the file system's in-memory copy
	// of recently written data to disk.
	func (f *File) Sync() error {
	if f == nil {
	return ErrInvalid
	}
	var d syscall.Dir
	d.Null()

	var buf [syscall.STATFIXLEN]byte
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &PathError{Op: "sync", Path: f.name, Err: err}
	}

	if err := f.incref("sync"); err != nil {
	return err
	}
	defer f.decref()

	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
	return &PathError{Op: "sync", Path: f.name, Err: err}
	}
	return nil
	}

	// 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) {
	if err := f.readLock(); err != nil {
	return 0, err
	}
	defer f.readUnlock()
	n, e := fixCount(syscall.Read(f.fd, b))
	if n == 0 && len(b) > 0 && e == nil {
	return 0, io.EOF
	}
	return n, e
	}

	// 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) {
	if err := f.readLock(); err != nil {
	return 0, err
	}
	defer f.readUnlock()
	n, e := fixCount(syscall.Pread(f.fd, b, off))
	if n == 0 && len(b) > 0 && e == nil {
	return 0, io.EOF
	}
	return n, e
	}

	// write writes len(b) bytes to the File.
	// It returns the number of bytes written and an error, if any.
	// Since Plan 9 preserves message boundaries, never allow
	// a zero-byte write.
	func (f *File) write(b []byte) (n int, err error) {
	if err := f.writeLock(); err != nil {
	return 0, err
	}
	defer f.writeUnlock()
	if len(b) == 0 {
	return 0, nil
	}
	return fixCount(syscall.Write(f.fd, b))
	}

	// 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.
	// Since Plan 9 preserves message boundaries, never allow
	// a zero-byte write.
	func (f *File) pwrite(b []byte, off int64) (n int, err error) {
	if err := f.writeLock(); err != nil {
	return 0, err
	}
	defer f.writeUnlock()
	if len(b) == 0 {
	return 0, nil
	}
	return fixCount(syscall.Pwrite(f.fd, b, off))
	}

	// 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) {
	if err := f.incref(""); err != nil {
	return 0, err
	}
	defer f.decref()
	// Free cached dirinfo, so we allocate a new one if we
	// access this file as a directory again. See #35767 and #37161.
	f.dirinfo.Store(nil)
	return syscall.Seek(f.fd, offset, whence)
	}

	// 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 {
	var d syscall.Dir

	d.Null()
	d.Length = size

	var buf [syscall.STATFIXLEN]byte
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &PathError{Op: "truncate", Path: name, Err: err}
	}
	if err = syscall.Wstat(name, buf[:n]); err != nil {
	return &PathError{Op: "truncate", Path: name, Err: err}
	}
	return nil
	}

	// Remove removes the named file or directory.
	// If there is an error, it will be of type *PathError.
	func Remove(name string) error {
	if e := syscall.Remove(name); e != nil {
	return &PathError{Op: "remove", Path: name, Err: e}
	}
	return nil
	}

	// hasPrefix from the strings package.
	func hasPrefix(s, prefix string) bool {
	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
	}

	func rename(oldname, newname string) error {
	dirname := oldname[:bytealg.LastIndexByteString(oldname, '/')+1]
	if hasPrefix(newname, dirname) {
	newname = newname[len(dirname):]
	} else {
	return &LinkError{"rename", oldname, newname, ErrInvalid}
	}

	// If newname still contains slashes after removing the oldname
	// prefix, the rename is cross-directory and must be rejected.
	if bytealg.LastIndexByteString(newname, '/') >= 0 {
	return &LinkError{"rename", oldname, newname, ErrInvalid}
	}

	var d syscall.Dir

	d.Null()
	d.Name = newname

	buf := make([]byte, syscall.STATFIXLEN+len(d.Name))
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &LinkError{"rename", oldname, newname, err}
	}

	// If newname already exists and is not a directory, rename replaces it.
	f, err := Stat(dirname + newname)
	if err == nil && !f.IsDir() {
	Remove(dirname + newname)
	}

	if err = syscall.Wstat(oldname, buf[:n]); err != nil {
	return &LinkError{"rename", oldname, newname, err}
	}
	return nil
	}

	// See docs in file.go:Chmod.
	func chmod(name string, mode FileMode) error {
	var d syscall.Dir

	odir, e := dirstat(name)
	if e != nil {
	return &PathError{Op: "chmod", Path: name, Err: e}
	}
	d.Null()
	d.Mode = odir.Mode&^chmodMask \| syscallMode(mode)&chmodMask

	var buf [syscall.STATFIXLEN]byte
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &PathError{Op: "chmod", Path: name, Err: err}
	}
	if err = syscall.Wstat(name, buf[:n]); err != nil {
	return &PathError{Op: "chmod", Path: name, Err: err}
	}
	return nil
	}

	// Chtimes changes the access and modification times of the named
	// file, similar to the Unix utime() or utimes() functions.
	// A zero time.Time value will leave the corresponding file time unchanged.
	//
	// The underlying filesystem may truncate or round the values to a
	// less precise time unit.
	// If there is an error, it will be of type *PathError.
	func Chtimes(name string, atime time.Time, mtime time.Time) error {
	var d syscall.Dir

	d.Null()
	d.Atime = uint32(atime.Unix())
	d.Mtime = uint32(mtime.Unix())
	if atime.IsZero() {
	d.Atime = 0xFFFFFFFF
	}
	if mtime.IsZero() {
	d.Mtime = 0xFFFFFFFF
	}

	var buf [syscall.STATFIXLEN]byte
	n, err := d.Marshal(buf[:])
	if err != nil {
	return &PathError{Op: "chtimes", Path: name, Err: err}
	}
	if err = syscall.Wstat(name, buf[:n]); err != nil {
	return &PathError{Op: "chtimes", Path: name, Err: err}
	}
	return nil
	}

	// Pipe returns a connected pair of Files; reads from r return bytes
	// written to w. It returns the files and an error, if any.
	func Pipe() (r File, w File, err error) {
	var p [2]int

	if e := syscall.Pipe(p[0:]); e != nil {
	return nil, nil, NewSyscallError("pipe", e)
	}

	return NewFile(uintptr(p[0]), "\|0"), NewFile(uintptr(p[1]), "\|1"), nil
	}

	// not supported on Plan 9

	// 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 {
	return &LinkError{"link", oldname, newname, syscall.EPLAN9}
	}

	// Symlink creates newname as a symbolic link to oldname.
	// On Windows, a symlink to a non-existent oldname creates a file symlink;
	// if oldname is later created as a directory the symlink will not work.
	// If there is an error, it will be of type *LinkError.
	func Symlink(oldname, newname string) error {
	return &LinkError{"symlink", oldname, newname, syscall.EPLAN9}
	}

	func readlink(name string) (string, error) {
	return "", &PathError{Op: "readlink", Path: name, Err: syscall.EPLAN9}
	}

	// Chown changes the numeric uid and gid of the named file.
	// If the file is a symbolic link, it changes the uid and gid of the link's target.
	// A uid or gid of -1 means to not change that value.
	// If there is an error, it will be of type *PathError.
	//
	// On Windows or Plan 9, Chown always returns the syscall.EWINDOWS or
	// EPLAN9 error, wrapped in *PathError.
	func Chown(name string, uid, gid int) error {
	return &PathError{Op: "chown", Path: name, Err: syscall.EPLAN9}
	}

	// Lchown changes the numeric uid and gid of the named file.
	// If the file is a symbolic link, it changes the uid and gid of the link itself.
	// If there is an error, it will be of type *PathError.
	func Lchown(name string, uid, gid int) error {
	return &PathError{Op: "lchown", Path: name, Err: syscall.EPLAN9}
	}

	// Chown changes the numeric uid and gid of the named file.
	// If there is an error, it will be of type *PathError.
	func (f *File) Chown(uid, gid int) error {
	if f == nil {
	return ErrInvalid
	}
	return &PathError{Op: "chown", Path: f.name, Err: syscall.EPLAN9}
	}

	func tempDir() string {
	dir := Getenv("TMPDIR")
	if dir == "" {
	dir = "/tmp"
	}
	return dir
	}

	// Chdir changes the current working directory to the file,
	// which must be a directory.
	// If there is an error, it will be of type *PathError.
	func (f *File) Chdir() error {
	if err := f.incref("chdir"); err != nil {
	return err
	}
	defer f.decref()
	if e := syscall.Fchdir(f.fd); e != nil {
	return &PathError{Op: "chdir", Path: f.name, Err: e}
	}
	return nil
	}

	// setDeadline sets the read and write deadline.
	func (f *File) setDeadline(time.Time) error {
	if err := f.checkValid("SetDeadline"); err != nil {
	return err
	}
	return poll.ErrNoDeadline
	}

	// setReadDeadline sets the read deadline.
	func (f *File) setReadDeadline(time.Time) error {
	if err := f.checkValid("SetReadDeadline"); err != nil {
	return err
	}
	return poll.ErrNoDeadline
	}

	// setWriteDeadline sets the write deadline.
	func (f *File) setWriteDeadline(time.Time) error {
	if err := f.checkValid("SetWriteDeadline"); err != nil {
	return err
	}
	return poll.ErrNoDeadline
	}

	// checkValid checks whether f is valid for use, but does not prepare
	// to actually use it. If f is not ready checkValid returns an appropriate
	// error, perhaps incorporating the operation name op.
	func (f *File) checkValid(op string) error {
	if f == nil {
	return ErrInvalid
	}
	if err := f.incref(op); err != nil {
	return err
	}
	return f.decref()
	}

	type rawConn struct{}

	func (c *rawConn) Control(f func(uintptr)) error {
	return syscall.EPLAN9
	}

	func (c *rawConn) Read(f func(uintptr) bool) error {
	return syscall.EPLAN9
	}

	func (c *rawConn) Write(f func(uintptr) bool) error {
	return syscall.EPLAN9
	}

	func newRawConn(file File) (rawConn, error) {
	return nil, syscall.EPLAN9
	}

	func ignoringEINTR(fn func() error) error {
	return fn()
	}