src/pkg/os/file_windows.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.

 package os

 import (
 	"io"
 	"runtime"
 	"sync"
 	"syscall"
 	"unicode/utf16"
 	"unicode/utf8"
 	"unsafe"
 )

 // File represents an open file descriptor.
 type File struct {
 	*file
 }

 // 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 {
 	fd      syscall.Handle
 	name    string
 	dirinfo *dirInfo   // nil unless directory being read
 	l       sync.Mutex // used to implement windows pread/pwrite

 	// only for console io
 	isConsole bool
 	lastbits  []byte // first few bytes of the last incomplete rune in last write
 	readbuf   []rune // input console buffer
 }

 // Fd returns the Windows handle referencing the open file.
 func (file *File) Fd() uintptr {
 	if file == nil {
 		return uintptr(syscall.InvalidHandle)
 	}
 	return uintptr(file.fd)
 }

 // newFile returns a new File with the given file handle and name.
 // Unlike NewFile, it does not check that h is syscall.InvalidHandle.
 func newFile(h syscall.Handle, name string) *File {
 	f := &File{&file{fd: h, name: name}}
 	var m uint32
 	if syscall.GetConsoleMode(f.fd, &m) == nil {
 		f.isConsole = true
 	}
 	runtime.SetFinalizer(f.file, (*file).close)
 	return f
 }

 // NewFile returns a new File with the given file descriptor and name.
 func NewFile(fd uintptr, name string) *File {
 	h := syscall.Handle(fd)
 	if h == syscall.InvalidHandle {
 		return nil
 	}
 	return newFile(h, name)
 }

 // Auxiliary information if the File describes a directory
 type dirInfo struct {
 	data     syscall.Win32finddata
 	needdata bool
 	path     string
 	isempty  bool // set if FindFirstFile returns ERROR_FILE_NOT_FOUND
 }

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

 const DevNull = "NUL"

 func (f *file) isdir() bool { return f != nil && f.dirinfo != nil }

 func openFile(name string, flag int, perm FileMode) (file *File, err error) {
 	r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
 	if e != nil {
 		return nil, e
 	}
 	return NewFile(uintptr(r), name), nil
 }

 func openDir(name string) (file *File, err error) {
 	maskp, e := syscall.UTF16PtrFromString(name + `\*`)
 	if e != nil {
 		return nil, e
 	}
 	d := new(dirInfo)
 	r, e := syscall.FindFirstFile(maskp, &d.data)
 	if e != nil {
 		// FindFirstFile returns ERROR_FILE_NOT_FOUND when
 		// no matching files can be found. Then, if directory
 		// exists, we should proceed.
 		if e != syscall.ERROR_FILE_NOT_FOUND {
 			return nil, e
 		}
 		var fa syscall.Win32FileAttributeData
 		namep, e := syscall.UTF16PtrFromString(name)
 		if e != nil {
 			return nil, e
 		}
 		e = syscall.GetFileAttributesEx(namep, syscall.GetFileExInfoStandard, (*byte)(unsafe.Pointer(&fa)))
 		if e != nil {
 			return nil, e
 		}
 		if fa.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY == 0 {
 			return nil, e
 		}
 		d.isempty = true
 	}
 	d.path = name
 	if !isAbs(d.path) {
 		cwd, _ := Getwd()
 		d.path = cwd + `\` + d.path
 	}
 	f := newFile(r, name)
 	f.dirinfo = d
 	return f, nil
 }

 // OpenFile is the generalized open call; most users will use Open
 // or Create instead.  It opens the named file with specified flag
 // (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful,
 // methods on the returned File can be used for I/O.
 // If there is an error, it will be of type *PathError.
 func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {
 	if name == "" {
 		return nil, &PathError{"open", name, syscall.ENOENT}
 	}
 	// TODO(brainman): not sure about my logic of assuming it is dir first, then fall back to file
 	r, e := openDir(name)
 	if e == nil {
 		if flag&O_WRONLY != 0 || flag&O_RDWR != 0 {
 			r.Close()
 			return nil, &PathError{"open", name, syscall.EISDIR}
 		}
 		return r, nil
 	}
 	r, e = openFile(name, flag, perm)
 	if e == nil {
 		return r, nil
 	}
 	return nil, &PathError{"open", name, e}
 }

 // Close closes the File, rendering it unusable for I/O.
 // It returns an error, if any.
 func (file *File) Close() error {
 	return file.file.close()
 }

 func (file *file) close() error {
 	if file == nil {
 		return syscall.EINVAL
 	}
 	if file.isdir() && file.dirinfo.isempty {
 		// "special" empty directories
 		return nil
 	}
 	if file.fd == syscall.InvalidHandle {
 		return syscall.EINVAL
 	}
 	var e error
 	if file.isdir() {
 		e = syscall.FindClose(syscall.Handle(file.fd))
 	} else {
 		e = syscall.CloseHandle(syscall.Handle(file.fd))
 	}
 	var err error
 	if e != nil {
 		err = &PathError{"close", file.name, e}
 	}
 	file.fd = syscall.InvalidHandle // so it can't be closed again

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

 func (file *File) readdir(n int) (fi []FileInfo, err error) {
 	if file == nil {
 		return nil, syscall.EINVAL
 	}
 	if !file.isdir() {
 		return nil, &PathError{"Readdir", file.name, syscall.ENOTDIR}
 	}
 	if !file.dirinfo.isempty && file.fd == syscall.InvalidHandle {
 		return nil, syscall.EINVAL
 	}
 	wantAll := n <= 0
 	size := n
 	if wantAll {
 		n = -1
 		size = 100
 	}
 	fi = make([]FileInfo, 0, size) // Empty with room to grow.
 	d := &file.dirinfo.data
 	for n != 0 && !file.dirinfo.isempty {
 		if file.dirinfo.needdata {
 			e := syscall.FindNextFile(syscall.Handle(file.fd), d)
 			if e != nil {
 				if e == syscall.ERROR_NO_MORE_FILES {
 					break
 				} else {
 					err = &PathError{"FindNextFile", file.name, e}
 					if !wantAll {
 						fi = nil
 					}
 					return
 				}
 			}
 		}
 		file.dirinfo.needdata = true
 		name := string(syscall.UTF16ToString(d.FileName[0:]))
 		if name == "." || name == ".." { // Useless names
 			continue
 		}
 		f := &fileStat{
 			name: name,
 			sys: syscall.Win32FileAttributeData{
 				FileAttributes: d.FileAttributes,
 				CreationTime:   d.CreationTime,
 				LastAccessTime: d.LastAccessTime,
 				LastWriteTime:  d.LastWriteTime,
 				FileSizeHigh:   d.FileSizeHigh,
 				FileSizeLow:    d.FileSizeLow,
 			},
 			path: file.dirinfo.path + `\` + name,
 		}
 		n--
 		fi = append(fi, f)
 	}
 	if !wantAll && len(fi) == 0 {
 		return fi, io.EOF
 	}
 	return fi, nil
 }

 // readConsole reads utf16 characters from console File,
 // encodes them into utf8 and stores them in buffer b.
 // It returns the number of utf8 bytes read and an error, if any.
 func (f *File) readConsole(b []byte) (n int, err error) {
 	if len(b) == 0 {
 		return 0, nil
 	}
 	if len(f.readbuf) == 0 {
 		// get more input data from os
 		wchars := make([]uint16, len(b))
 		var p *uint16
 		if len(b) > 0 {
 			p = &wchars[0]
 		}
 		var nw uint32
 		err := syscall.ReadConsole(f.fd, p, uint32(len(wchars)), &nw, nil)
 		if err != nil {
 			return 0, err
 		}
 		f.readbuf = utf16.Decode(wchars[:nw])
 	}
 	for i, r := range f.readbuf {
 		if utf8.RuneLen(r) > len(b) {
 			f.readbuf = f.readbuf[i:]
 			return n, nil
 		}
 		nr := utf8.EncodeRune(b, r)
 		b = b[nr:]
 		n += nr
 	}
 	f.readbuf = nil
 	return n, 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) {
 	f.l.Lock()
 	defer f.l.Unlock()
 	if f.isConsole {
 		return f.readConsole(b)
 	}
 	return syscall.Read(f.fd, b)
 }

 // 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 0.
 func (f *File) pread(b []byte, off int64) (n int, err error) {
 	f.l.Lock()
 	defer f.l.Unlock()
 	curoffset, e := syscall.Seek(f.fd, 0, 1)
 	if e != nil {
 		return 0, e
 	}
 	defer syscall.Seek(f.fd, curoffset, 0)
 	o := syscall.Overlapped{
 		OffsetHigh: uint32(off >> 32),
 		Offset:     uint32(off),
 	}
 	var done uint32
 	e = syscall.ReadFile(syscall.Handle(f.fd), b, &done, &o)
 	if e != nil {
 		return 0, e
 	}
 	return int(done), nil
 }

 // writeConsole writes len(b) bytes to the console File.
 // It returns the number of bytes written and an error, if any.
 func (f *File) writeConsole(b []byte) (n int, err error) {
 	n = len(b)
 	runes := make([]rune, 0, 256)
 	if len(f.lastbits) > 0 {
 		b = append(f.lastbits, b...)
 		f.lastbits = nil

 	}
 	for len(b) >= utf8.UTFMax || utf8.FullRune(b) {
 		r, l := utf8.DecodeRune(b)
 		runes = append(runes, r)
 		b = b[l:]
 	}
 	if len(b) > 0 {
 		f.lastbits = make([]byte, len(b))
 		copy(f.lastbits, b)
 	}
 	// syscall.WriteConsole seems to fail, if given large buffer.
 	// So limit the buffer to 16000 characters. This number was
 	// discovered by experimenting with syscall.WriteConsole.
 	const maxWrite = 16000
 	for len(runes) > 0 {
 		m := len(runes)
 		if m > maxWrite {
 			m = maxWrite
 		}
 		chunk := runes[:m]
 		runes = runes[m:]
 		uint16s := utf16.Encode(chunk)
 		for len(uint16s) > 0 {
 			var written uint32
 			err = syscall.WriteConsole(f.fd, &uint16s[0], uint32(len(uint16s)), &written, nil)
 			if err != nil {
 				return 0, nil
 			}
 			uint16s = uint16s[written:]
 		}
 	}
 	return n, nil
 }

 // 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) {
 	f.l.Lock()
 	defer f.l.Unlock()
 	if f.isConsole {
 		return f.writeConsole(b)
 	}
 	return 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.
 func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 	f.l.Lock()
 	defer f.l.Unlock()
 	curoffset, e := syscall.Seek(f.fd, 0, 1)
 	if e != nil {
 		return 0, e
 	}
 	defer syscall.Seek(f.fd, curoffset, 0)
 	o := syscall.Overlapped{
 		OffsetHigh: uint32(off >> 32),
 		Offset:     uint32(off),
 	}
 	var done uint32
 	e = syscall.WriteFile(syscall.Handle(f.fd), b, &done, &o)
 	if e != nil {
 		return 0, e
 	}
 	return int(done), nil
 }

 // 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) {
 	f.l.Lock()
 	defer f.l.Unlock()
 	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.
 func Truncate(name string, size int64) error {
 	f, e := OpenFile(name, O_WRONLY|O_CREATE, 0666)
 	if e != nil {
 		return e
 	}
 	defer f.Close()
 	e1 := f.Truncate(size)
 	if e1 != nil {
 		return e1
 	}
 	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 {
 	p, e := syscall.UTF16PtrFromString(name)
 	if e != nil {
 		return &PathError{"remove", name, e}
 	}

 	// Go file interface forces us to know whether
 	// name is a file or directory. Try both.
 	e = syscall.DeleteFile(p)
 	if e == nil {
 		return nil
 	}
 	e1 := syscall.RemoveDirectory(p)
 	if e1 == nil {
 		return nil
 	}

 	// Both failed: figure out which error to return.
 	if e1 != e {
 		a, e2 := syscall.GetFileAttributes(p)
 		if e2 != nil {
 			e = e2
 		} else {
 			if a&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
 				e = e1
 			}
 		}
 	}
 	return &PathError{"remove", name, e}
 }

 // 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]syscall.Handle

 	// See ../syscall/exec.go for description of lock.
 	syscall.ForkLock.RLock()
 	e := syscall.Pipe(p[0:])
 	if e != nil {
 		syscall.ForkLock.RUnlock()
 		return nil, nil, NewSyscallError("pipe", e)
 	}
 	syscall.CloseOnExec(p[0])
 	syscall.CloseOnExec(p[1])
 	syscall.ForkLock.RUnlock()

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

 // TempDir returns the default directory to use for temporary files.
 func TempDir() string {
 	const pathSep = '\\'
 	dirw := make([]uint16, syscall.MAX_PATH)
 	n, _ := syscall.GetTempPath(uint32(len(dirw)), &dirw[0])
 	if n > uint32(len(dirw)) {
 		dirw = make([]uint16, n)
 		n, _ = syscall.GetTempPath(uint32(len(dirw)), &dirw[0])
 		if n > uint32(len(dirw)) {
 			n = 0
 		}
 	}
 	if n > 0 && dirw[n-1] == pathSep {
 		n--
 	}
 	return string(utf16.Decode(dirw[0:n]))
 }
	// 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"
	"sync"
	"syscall"
	"unicode/utf16"
	"unicode/utf8"
	"unsafe"
	)

	// File represents an open file descriptor.
	type File struct {
	*file
	}

	// 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 {
	fd syscall.Handle
	name string
	dirinfo *dirInfo // nil unless directory being read
	l sync.Mutex // used to implement windows pread/pwrite

	// only for console io
	isConsole bool
	lastbits []byte // first few bytes of the last incomplete rune in last write
	readbuf []rune // input console buffer
	}

	// Fd returns the Windows handle referencing the open file.
	func (file *File) Fd() uintptr {
	if file == nil {
	return uintptr(syscall.InvalidHandle)
	}
	return uintptr(file.fd)
	}

	// newFile returns a new File with the given file handle and name.
	// Unlike NewFile, it does not check that h is syscall.InvalidHandle.
	func newFile(h syscall.Handle, name string) *File {
	f := &File{&file{fd: h, name: name}}
	var m uint32
	if syscall.GetConsoleMode(f.fd, &m) == nil {
	f.isConsole = true
	}
	runtime.SetFinalizer(f.file, (*file).close)
	return f
	}

	// NewFile returns a new File with the given file descriptor and name.
	func NewFile(fd uintptr, name string) *File {
	h := syscall.Handle(fd)
	if h == syscall.InvalidHandle {
	return nil
	}
	return newFile(h, name)
	}

	// Auxiliary information if the File describes a directory
	type dirInfo struct {
	data syscall.Win32finddata
	needdata bool
	path string
	isempty bool // set if FindFirstFile returns ERROR_FILE_NOT_FOUND
	}

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

	const DevNull = "NUL"

	func (f *file) isdir() bool { return f != nil && f.dirinfo != nil }

	func openFile(name string, flag int, perm FileMode) (file *File, err error) {
	r, e := syscall.Open(name, flag\|syscall.O_CLOEXEC, syscallMode(perm))
	if e != nil {
	return nil, e
	}
	return NewFile(uintptr(r), name), nil
	}

	func openDir(name string) (file *File, err error) {
	maskp, e := syscall.UTF16PtrFromString(name + `\*`)
	if e != nil {
	return nil, e
	}
	d := new(dirInfo)
	r, e := syscall.FindFirstFile(maskp, &d.data)
	if e != nil {
	// FindFirstFile returns ERROR_FILE_NOT_FOUND when
	// no matching files can be found. Then, if directory
	// exists, we should proceed.
	if e != syscall.ERROR_FILE_NOT_FOUND {
	return nil, e
	}
	var fa syscall.Win32FileAttributeData
	namep, e := syscall.UTF16PtrFromString(name)
	if e != nil {
	return nil, e
	}
	e = syscall.GetFileAttributesEx(namep, syscall.GetFileExInfoStandard, (*byte)(unsafe.Pointer(&fa)))
	if e != nil {
	return nil, e
	}
	if fa.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY == 0 {
	return nil, e
	}
	d.isempty = true
	}
	d.path = name
	if !isAbs(d.path) {
	cwd, _ := Getwd()
	d.path = cwd + `\` + d.path
	}
	f := newFile(r, name)
	f.dirinfo = d
	return f, nil
	}

	// OpenFile is the generalized open call; most users will use Open
	// or Create instead. It opens the named file with specified flag
	// (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful,
	// methods on the returned File can be used for I/O.
	// If there is an error, it will be of type *PathError.
	func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {
	if name == "" {
	return nil, &PathError{"open", name, syscall.ENOENT}
	}
	// TODO(brainman): not sure about my logic of assuming it is dir first, then fall back to file
	r, e := openDir(name)
	if e == nil {
	if flag&O_WRONLY != 0 \|\| flag&O_RDWR != 0 {
	r.Close()
	return nil, &PathError{"open", name, syscall.EISDIR}
	}
	return r, nil
	}
	r, e = openFile(name, flag, perm)
	if e == nil {
	return r, nil
	}
	return nil, &PathError{"open", name, e}
	}

	// Close closes the File, rendering it unusable for I/O.
	// It returns an error, if any.
	func (file *File) Close() error {
	return file.file.close()
	}

	func (file *file) close() error {
	if file == nil {
	return syscall.EINVAL
	}
	if file.isdir() && file.dirinfo.isempty {
	// "special" empty directories
	return nil
	}
	if file.fd == syscall.InvalidHandle {
	return syscall.EINVAL
	}
	var e error
	if file.isdir() {
	e = syscall.FindClose(syscall.Handle(file.fd))
	} else {
	e = syscall.CloseHandle(syscall.Handle(file.fd))
	}
	var err error
	if e != nil {
	err = &PathError{"close", file.name, e}
	}
	file.fd = syscall.InvalidHandle // so it can't be closed again

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

	func (file *File) readdir(n int) (fi []FileInfo, err error) {
	if file == nil {
	return nil, syscall.EINVAL
	}
	if !file.isdir() {
	return nil, &PathError{"Readdir", file.name, syscall.ENOTDIR}
	}
	if !file.dirinfo.isempty && file.fd == syscall.InvalidHandle {
	return nil, syscall.EINVAL
	}
	wantAll := n <= 0
	size := n
	if wantAll {
	n = -1
	size = 100
	}
	fi = make([]FileInfo, 0, size) // Empty with room to grow.
	d := &file.dirinfo.data
	for n != 0 && !file.dirinfo.isempty {
	if file.dirinfo.needdata {
	e := syscall.FindNextFile(syscall.Handle(file.fd), d)
	if e != nil {
	if e == syscall.ERROR_NO_MORE_FILES {
	break
	} else {
	err = &PathError{"FindNextFile", file.name, e}
	if !wantAll {
	fi = nil
	}
	return
	}
	}
	}
	file.dirinfo.needdata = true
	name := string(syscall.UTF16ToString(d.FileName[0:]))
	if name == "." \|\| name == ".." { // Useless names
	continue
	}
	f := &fileStat{
	name: name,
	sys: syscall.Win32FileAttributeData{
	FileAttributes: d.FileAttributes,
	CreationTime: d.CreationTime,
	LastAccessTime: d.LastAccessTime,
	LastWriteTime: d.LastWriteTime,
	FileSizeHigh: d.FileSizeHigh,
	FileSizeLow: d.FileSizeLow,
	},
	path: file.dirinfo.path + `\` + name,
	}
	n--
	fi = append(fi, f)
	}
	if !wantAll && len(fi) == 0 {
	return fi, io.EOF
	}
	return fi, nil
	}

	// readConsole reads utf16 characters from console File,
	// encodes them into utf8 and stores them in buffer b.
	// It returns the number of utf8 bytes read and an error, if any.
	func (f *File) readConsole(b []byte) (n int, err error) {
	if len(b) == 0 {
	return 0, nil
	}
	if len(f.readbuf) == 0 {
	// get more input data from os
	wchars := make([]uint16, len(b))
	var p *uint16
	if len(b) > 0 {
	p = &wchars[0]
	}
	var nw uint32
	err := syscall.ReadConsole(f.fd, p, uint32(len(wchars)), &nw, nil)
	if err != nil {
	return 0, err
	}
	f.readbuf = utf16.Decode(wchars[:nw])
	}
	for i, r := range f.readbuf {
	if utf8.RuneLen(r) > len(b) {
	f.readbuf = f.readbuf[i:]
	return n, nil
	}
	nr := utf8.EncodeRune(b, r)
	b = b[nr:]
	n += nr
	}
	f.readbuf = nil
	return n, 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) {
	f.l.Lock()
	defer f.l.Unlock()
	if f.isConsole {
	return f.readConsole(b)
	}
	return syscall.Read(f.fd, b)
	}

	// 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 0.
	func (f *File) pread(b []byte, off int64) (n int, err error) {
	f.l.Lock()
	defer f.l.Unlock()
	curoffset, e := syscall.Seek(f.fd, 0, 1)
	if e != nil {
	return 0, e
	}
	defer syscall.Seek(f.fd, curoffset, 0)
	o := syscall.Overlapped{
	OffsetHigh: uint32(off >> 32),
	Offset: uint32(off),
	}
	var done uint32
	e = syscall.ReadFile(syscall.Handle(f.fd), b, &done, &o)
	if e != nil {
	return 0, e
	}
	return int(done), nil
	}

	// writeConsole writes len(b) bytes to the console File.
	// It returns the number of bytes written and an error, if any.
	func (f *File) writeConsole(b []byte) (n int, err error) {
	n = len(b)
	runes := make([]rune, 0, 256)
	if len(f.lastbits) > 0 {
	b = append(f.lastbits, b...)
	f.lastbits = nil

	}
	for len(b) >= utf8.UTFMax \|\| utf8.FullRune(b) {
	r, l := utf8.DecodeRune(b)
	runes = append(runes, r)
	b = b[l:]
	}
	if len(b) > 0 {
	f.lastbits = make([]byte, len(b))
	copy(f.lastbits, b)
	}
	// syscall.WriteConsole seems to fail, if given large buffer.
	// So limit the buffer to 16000 characters. This number was
	// discovered by experimenting with syscall.WriteConsole.
	const maxWrite = 16000
	for len(runes) > 0 {
	m := len(runes)
	if m > maxWrite {
	m = maxWrite
	}
	chunk := runes[:m]
	runes = runes[m:]
	uint16s := utf16.Encode(chunk)
	for len(uint16s) > 0 {
	var written uint32
	err = syscall.WriteConsole(f.fd, &uint16s[0], uint32(len(uint16s)), &written, nil)
	if err != nil {
	return 0, nil
	}
	uint16s = uint16s[written:]
	}
	}
	return n, nil
	}

	// 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) {
	f.l.Lock()
	defer f.l.Unlock()
	if f.isConsole {
	return f.writeConsole(b)
	}
	return 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.
	func (f *File) pwrite(b []byte, off int64) (n int, err error) {
	f.l.Lock()
	defer f.l.Unlock()
	curoffset, e := syscall.Seek(f.fd, 0, 1)
	if e != nil {
	return 0, e
	}
	defer syscall.Seek(f.fd, curoffset, 0)
	o := syscall.Overlapped{
	OffsetHigh: uint32(off >> 32),
	Offset: uint32(off),
	}
	var done uint32
	e = syscall.WriteFile(syscall.Handle(f.fd), b, &done, &o)
	if e != nil {
	return 0, e
	}
	return int(done), nil
	}

	// 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) {
	f.l.Lock()
	defer f.l.Unlock()
	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.
	func Truncate(name string, size int64) error {
	f, e := OpenFile(name, O_WRONLY\|O_CREATE, 0666)
	if e != nil {
	return e
	}
	defer f.Close()
	e1 := f.Truncate(size)
	if e1 != nil {
	return e1
	}
	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 {
	p, e := syscall.UTF16PtrFromString(name)
	if e != nil {
	return &PathError{"remove", name, e}
	}

	// Go file interface forces us to know whether
	// name is a file or directory. Try both.
	e = syscall.DeleteFile(p)
	if e == nil {
	return nil
	}
	e1 := syscall.RemoveDirectory(p)
	if e1 == nil {
	return nil
	}

	// Both failed: figure out which error to return.
	if e1 != e {
	a, e2 := syscall.GetFileAttributes(p)
	if e2 != nil {
	e = e2
	} else {
	if a&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
	e = e1
	}
	}
	}
	return &PathError{"remove", name, e}
	}

	// 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]syscall.Handle

	// See ../syscall/exec.go for description of lock.
	syscall.ForkLock.RLock()
	e := syscall.Pipe(p[0:])
	if e != nil {
	syscall.ForkLock.RUnlock()
	return nil, nil, NewSyscallError("pipe", e)
	}
	syscall.CloseOnExec(p[0])
	syscall.CloseOnExec(p[1])
	syscall.ForkLock.RUnlock()

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

	// TempDir returns the default directory to use for temporary files.
	func TempDir() string {
	const pathSep = '\\'
	dirw := make([]uint16, syscall.MAX_PATH)
	n, _ := syscall.GetTempPath(uint32(len(dirw)), &dirw[0])
	if n > uint32(len(dirw)) {
	dirw = make([]uint16, n)
	n, _ = syscall.GetTempPath(uint32(len(dirw)), &dirw[0])
	if n > uint32(len(dirw)) {
	n = 0
	}
	}
	if n > 0 && dirw[n-1] == pathSep {
	n--
	}
	return string(utf16.Decode(dirw[0:n]))
	}