// 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 (
"errors"
"internal/poll"
"internal/syscall/windows"
"runtime"
"syscall"
"unicode/utf16"
"unsafe"
)
// 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
appendMode bool // whether file is opened for appending
}
// Fd returns the Windows handle referencing the open file.
// The handle 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 (file *File) Fd() uintptr {
if file == nil {
return uintptr(syscall.InvalidHandle)
}
return uintptr(file.pfd.Sysfd)
}
// 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, kind string) *File {
if kind == "file" {
var m uint32
if syscall.GetConsoleMode(h, &m) == nil {
kind = "console"
}
if t, err := syscall.GetFileType(h); err == nil && t == syscall.FILE_TYPE_PIPE {
kind = "pipe"
}
}
f := &File{&file{
pfd: poll.FD{
Sysfd: h,
IsStream: true,
ZeroReadIsEOF: true,
},
name: name,
}}
runtime.SetFinalizer(f.file, (*file).close)
// Ignore initialization errors.
// Assume any problems will show up in later I/O.
f.pfd.Init(kind, false)
return f
}
// newConsoleFile creates new File that will be used as console.
func newConsoleFile(h syscall.Handle, name string) *File {
return newFile(h, name, "console")
}
// 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 {
h := syscall.Handle(fd)
if h == syscall.InvalidHandle {
return nil
}
return newFile(h, name, "file")
}
// 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) {
}
// DevNull is the name of the operating system's ``null device.''
// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
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(fixLongPath(name), flag|syscall.O_CLOEXEC, syscallMode(perm))
if e != nil {
return nil, e
}
return newFile(r, name, "file"), nil
}
func openDir(name string) (file *File, err error) {
var mask string
path := fixLongPath(name)
if len(path) == 2 && path[1] == ':' || (len(path) > 0 && path[len(path)-1] == '\\') { // it is a drive letter, like C:
mask = path + `*`
} else {
mask = path + `\*`
}
maskp, e := syscall.UTF16PtrFromString(mask)
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
pathp, e := syscall.UTF16PtrFromString(path)
if e != nil {
return nil, e
}
e = syscall.GetFileAttributesEx(pathp, 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 = path
if !isAbs(d.path) {
d.path, e = syscall.FullPath(d.path)
if e != nil {
return nil, e
}
}
f := newFile(r, name, "dir")
f.dirinfo = d
return f, nil
}
// openFileNolog is the Windows implementation of OpenFile.
func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
if name == "" {
return nil, &PathError{"open", name, syscall.ENOENT}
}
r, errf := openFile(name, flag, perm)
if errf == nil {
return r, nil
}
r, errd := openDir(name)
if errd == nil {
if flag&O_WRONLY != 0 || flag&O_RDWR != 0 {
r.Close()
return nil, &PathError{"open", name, syscall.EISDIR}
}
return r, nil
}
return nil, &PathError{"open", name, errf}
}
// 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.
// Close will return an error if it has already been called.
func (file *File) Close() error {
if file == nil {
return ErrInvalid
}
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
}
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 0.
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.
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(fixLongPath(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
} else if a&syscall.FILE_ATTRIBUTE_READONLY != 0 {
if e1 = syscall.SetFileAttributes(p, a&^syscall.FILE_ATTRIBUTE_READONLY); e1 == nil {
if e = syscall.DeleteFile(p); e == nil {
return nil
}
}
}
}
}
return &PathError{"remove", name, e}
}
func rename(oldname, newname string) error {
e := windows.Rename(fixLongPath(oldname), fixLongPath(newname))
if e != nil {
return &LinkError{"rename", oldname, newname, e}
}
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]syscall.Handle
e := syscall.CreatePipe(&p[0], &p[1], nil, 0)
if e != nil {
return nil, nil, NewSyscallError("pipe", e)
}
return newFile(p[0], "|0", "pipe"), newFile(p[1], "|1", "pipe"), nil
}
func tempDir() string {
n := uint32(syscall.MAX_PATH)
for {
b := make([]uint16, n)
n, _ = syscall.GetTempPath(uint32(len(b)), &b[0])
if n > uint32(len(b)) {
continue
}
if n == 3 && b[1] == ':' && b[2] == '\\' {
// Do nothing for path, like C:\.
} else if n > 0 && b[n-1] == '\\' {
// Otherwise remove terminating \.
n--
}
return string(utf16.Decode(b[:n]))
}
}
// 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 {
n, err := syscall.UTF16PtrFromString(fixLongPath(newname))
if err != nil {
return &LinkError{"link", oldname, newname, err}
}
o, err := syscall.UTF16PtrFromString(fixLongPath(oldname))
if err != nil {
return &LinkError{"link", oldname, newname, err}
}
err = syscall.CreateHardLink(n, o, 0)
if err != nil {
return &LinkError{"link", oldname, newname, err}
}
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 {
// '/' does not work in link's content
oldname = fromSlash(oldname)
// need the exact location of the oldname when it's relative to determine if it's a directory
destpath := oldname
if !isAbs(oldname) {
destpath = dirname(newname) + `\` + oldname
}
fi, err := Stat(destpath)
isdir := err == nil && fi.IsDir()
n, err := syscall.UTF16PtrFromString(fixLongPath(newname))
if err != nil {
return &LinkError{"symlink", oldname, newname, err}
}
o, err := syscall.UTF16PtrFromString(fixLongPath(oldname))
if err != nil {
return &LinkError{"symlink", oldname, newname, err}
}
var flags uint32 = windows.SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
if isdir {
flags |= syscall.SYMBOLIC_LINK_FLAG_DIRECTORY
}
err = syscall.CreateSymbolicLink(n, o, flags)
if err != nil {
// the unprivileged create flag is unsupported
// below Windows 10 (1703, v10.0.14972). retry without it.
flags &^= windows.SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
err = syscall.CreateSymbolicLink(n, o, flags)
}
if err != nil {
return &LinkError{"symlink", oldname, newname, err}
}
return nil
}
// openSymlink calls CreateFile Windows API with FILE_FLAG_OPEN_REPARSE_POINT
// parameter, so that Windows does not follow symlink, if path is a symlink.
// openSymlink returns opened file handle.
func openSymlink(path string) (syscall.Handle, error) {
p, err := syscall.UTF16PtrFromString(path)
if err != nil {
return 0, err
}
attrs := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS)
// Use FILE_FLAG_OPEN_REPARSE_POINT, otherwise CreateFile will follow symlink.
// See https://docs.microsoft.com/en-us/windows/desktop/FileIO/symbolic-link-effects-on-file-systems-functions#createfile-and-createfiletransacted
attrs |= syscall.FILE_FLAG_OPEN_REPARSE_POINT
h, err := syscall.CreateFile(p, 0, 0, nil, syscall.OPEN_EXISTING, attrs, 0)
if err != nil {
return 0, err
}
return h, nil
}
// normaliseLinkPath converts absolute paths returned by
// DeviceIoControl(h, FSCTL_GET_REPARSE_POINT, ...)
// into paths acceptable by all Windows APIs.
// For example, it coverts
// \??\C:\foo\bar into C:\foo\bar
// \??\UNC\foo\bar into \\foo\bar
// \??\Volume{abc}\ into C:\
func normaliseLinkPath(path string) (string, error) {
if len(path) < 4 || path[:4] != `\??\` {
// unexpected path, return it as is
return path, nil
}
// we have path that start with \??\
s := path[4:]
switch {
case len(s) >= 2 && s[1] == ':': // \??\C:\foo\bar
return s, nil
case len(s) >= 4 && s[:4] == `UNC\`: // \??\UNC\foo\bar
return `\\` + s[4:], nil
}
// handle paths, like \??\Volume{abc}\...
err := windows.LoadGetFinalPathNameByHandle()
if err != nil {
// we must be using old version of Windows
return "", err
}
h, err := openSymlink(path)
if err != nil {
return "", err
}
defer syscall.CloseHandle(h)
buf := make([]uint16, 100)
for {
n, err := windows.GetFinalPathNameByHandle(h, &buf[0], uint32(len(buf)), windows.VOLUME_NAME_DOS)
if err != nil {
return "", err
}
if n < uint32(len(buf)) {
break
}
buf = make([]uint16, n)
}
s = syscall.UTF16ToString(buf)
if len(s) > 4 && s[:4] == `\\?\` {
s = s[4:]
if len(s) > 3 && s[:3] == `UNC` {
// return path like \\server\share\...
return `\` + s[3:], nil
}
return s, nil
}
return "", errors.New("GetFinalPathNameByHandle returned unexpected path: " + s)
}
func readlink(path string) (string, error) {
h, err := openSymlink(path)
if err != nil {
return "", err
}
defer syscall.CloseHandle(h)
rdbbuf := make([]byte, syscall.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
var bytesReturned uint32
err = syscall.DeviceIoControl(h, syscall.FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
if err != nil {
return "", err
}
rdb := (*windows.REPARSE_DATA_BUFFER)(unsafe.Pointer(&rdbbuf[0]))
switch rdb.ReparseTag {
case syscall.IO_REPARSE_TAG_SYMLINK:
rb := (*windows.SymbolicLinkReparseBuffer)(unsafe.Pointer(&rdb.DUMMYUNIONNAME))
s := rb.Path()
if rb.Flags&windows.SYMLINK_FLAG_RELATIVE != 0 {
return s, nil
}
return normaliseLinkPath(s)
case windows.IO_REPARSE_TAG_MOUNT_POINT:
return normaliseLinkPath((*windows.MountPointReparseBuffer)(unsafe.Pointer(&rdb.DUMMYUNIONNAME)).Path())
default:
// the path is not a symlink or junction but another type of reparse
// point
return "", syscall.ENOENT
}
}
// 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) {
s, err := readlink(fixLongPath(name))
if err != nil {
return "", &PathError{"readlink", name, err}
}
return s, nil
}
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