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// 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 (
"runtime"
"syscall"
"time"
)
// 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 int
name string
dirinfo *dirInfo // nil unless directory being read
}
// Fd returns the integer Unix file descriptor referencing the open file.
func (file *File) Fd() int {
if file == nil {
return -1
}
return file.fd
}
// NewFile returns a new File with the given file descriptor and name.
func NewFile(fd int, name string) *File {
if fd < 0 {
return nil
}
f := &File{&file{fd: fd, name: name}}
runtime.SetFinalizer(f.file, (*file).close)
return f
}
// Auxiliary information if the File describes a directory
type dirInfo struct {
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
}
// 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) {
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
}
syscall.ForkLock.RLock()
if (create && trunc) || excl {
fd, e = syscall.Create(name, flag, syscallMode(perm))
} else {
fd, e = syscall.Open(name, flag)
if e != nil && create {
var e1 error
fd, e1 = syscall.Create(name, flag, syscallMode(perm))
if e1 == nil {
e = nil
}
}
}
syscall.ForkLock.RUnlock()
if e != nil {
return nil, &PathError{"open", name, e}
}
if append {
if _, e = syscall.Seek(fd, 0, SEEK_END); e != nil {
return nil, &PathError{"seek", name, e}
}
}
return NewFile(fd, name), nil
}
// 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 || file.fd < 0 {
return Ebadfd
}
var err error
syscall.ForkLock.RLock()
if e := syscall.Close(file.fd); e != nil {
err = &PathError{"close", file.name, e}
}
syscall.ForkLock.RUnlock()
file.fd = -1 // so it can't be closed again
// no need for a finalizer anymore
runtime.SetFinalizer(file, nil)
return err
}
// Stat returns the FileInfo structure describing file.
// It returns the FileInfo and an error, if any.
func (f *File) Stat() (FileInfo, error) {
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.
func (f *File) Truncate(size int64) error {
var d Dir
d.Null()
d.Length = uint64(size)
if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {
return &PathError{"truncate", f.name, e}
}
return nil
}
const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)
// Chmod changes the mode of the file to mode.
// If there is an error, it will be of type *PathError.
func (f *File) Chmod(mode FileMode) error {
var d Dir
odir, e := dirstat(f)
if e != nil {
return &PathError{"chmod", f.name, e}
}
d.Null()
d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {
return &PathError{"chmod", f.name, e}
}
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() (err error) {
if f == nil {
return EINVAL
}
var d Dir
d.Null()
if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {
return NewSyscallError("fsync", e)
}
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) {
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 nil.
func (f *File) pread(b []byte, off int64) (n int, err error) {
return syscall.Pread(f.fd, b, off)
}
// 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) {
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) {
return 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) {
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 Dir
d.Null()
d.Length = uint64(size)
if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {
return &PathError{"truncate", name, e}
}
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{"remove", name, e}
}
return nil
}
// Rename renames a file.
// If there is an error, it will be of type *PathError.
func Rename(oldname, newname string) error {
var d Dir
d.Null()
d.Name = newname
if e := syscall.Wstat(oldname, pdir(nil, &d)); e != nil {
return &PathError{"rename", oldname, e}
}
return nil
}
// Chmod changes the mode of the named file to mode.
// If there is an error, it will be of type *PathError.
func Chmod(name string, mode FileMode) error {
var d Dir
odir, e := dirstat(name)
if e != nil {
return &PathError{"chmod", name, e}
}
d.Null()
d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {
return &PathError{"chmod", name, e}
}
return nil
}
// Chtimes changes the access and modification times of the named
// file, similar to the Unix utime() or utimes() functions.
//
// The underlying filesystem may truncate or round the values to a
// less precise time unit.
func Chtimes(name string, atime time.Time, mtime time.Time) error {
var d Dir
d.Null()
d.Atime = uint32(atime.Unix())
d.Mtime = uint32(mtime.Unix())
if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {
return &PathError{"chtimes", name, e}
}
return nil
}
func Pipe() (r *File, w *File, err error) {
var p [2]int
syscall.ForkLock.RLock()
if e := syscall.Pipe(p[0:]); e != nil {
syscall.ForkLock.RUnlock()
return nil, nil, NewSyscallError("pipe", e)
}
syscall.ForkLock.RUnlock()
return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
}
// not supported on Plan 9
// Link creates a hard link.
func Link(oldname, newname string) error {
return EPLAN9
}
func Symlink(oldname, newname string) error {
return EPLAN9
}
func Readlink(name string) (string, error) {
return "", EPLAN9
}
func Chown(name string, uid, gid int) error {
return EPLAN9
}
func Lchown(name string, uid, gid int) error {
return EPLAN9
}
func (f *File) Chown(uid, gid int) error {
return EPLAN9
}
// TempDir returns the default directory to use for temporary files.
func TempDir() string {
return "/tmp"
}