362 lines
8.5 KiB
Go
362 lines
8.5 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package os
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import (
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"runtime"
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"syscall"
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"time"
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)
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// File represents an open file descriptor.
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type File struct {
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*file
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}
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// file is the real representation of *File.
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// The extra level of indirection ensures that no clients of os
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// can overwrite this data, which could cause the finalizer
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// to close the wrong file descriptor.
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type file struct {
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fd int
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name string
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dirinfo *dirInfo // nil unless directory being read
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}
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// Fd returns the integer Unix file descriptor referencing the open file.
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func (file *File) Fd() int {
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if file == nil {
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return -1
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}
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return file.fd
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}
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// NewFile returns a new File with the given file descriptor and name.
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func NewFile(fd int, name string) *File {
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if fd < 0 {
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return nil
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}
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f := &File{&file{fd: fd, name: name}}
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runtime.SetFinalizer(f.file, (*file).close)
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return f
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}
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// Auxiliary information if the File describes a directory
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type dirInfo struct {
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buf [syscall.STATMAX]byte // buffer for directory I/O
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nbuf int // length of buf; return value from Read
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bufp int // location of next record in buf.
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}
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func epipecheck(file *File, e error) {
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}
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// DevNull is the name of the operating system's ``null device.''
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// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
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const DevNull = "/dev/null"
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// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
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func syscallMode(i FileMode) (o uint32) {
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o |= uint32(i.Perm())
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if i&ModeAppend != 0 {
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o |= syscall.DMAPPEND
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}
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if i&ModeExclusive != 0 {
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o |= syscall.DMEXCL
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}
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if i&ModeTemporary != 0 {
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o |= syscall.DMTMP
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}
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return
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}
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// OpenFile is the generalized open call; most users will use Open
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// or Create instead. It opens the named file with specified flag
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// (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful,
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// methods on the returned File can be used for I/O.
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// It returns the File and an error, if any.
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func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {
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var (
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fd int
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e error
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create bool
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excl bool
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trunc bool
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append bool
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)
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if flag&O_CREATE == O_CREATE {
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flag = flag & ^O_CREATE
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create = true
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}
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if flag&O_EXCL == O_EXCL {
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excl = true
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}
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if flag&O_TRUNC == O_TRUNC {
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trunc = true
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}
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// O_APPEND is emulated on Plan 9
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if flag&O_APPEND == O_APPEND {
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flag = flag &^ O_APPEND
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append = true
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}
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syscall.ForkLock.RLock()
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if (create && trunc) || excl {
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fd, e = syscall.Create(name, flag, syscallMode(perm))
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} else {
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fd, e = syscall.Open(name, flag)
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if e != nil && create {
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var e1 error
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fd, e1 = syscall.Create(name, flag, syscallMode(perm))
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if e1 == nil {
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e = nil
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}
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}
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}
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syscall.ForkLock.RUnlock()
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if e != nil {
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return nil, &PathError{"open", name, e}
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}
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if append {
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if _, e = syscall.Seek(fd, 0, SEEK_END); e != nil {
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return nil, &PathError{"seek", name, e}
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}
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}
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return NewFile(fd, name), nil
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}
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// Close closes the File, rendering it unusable for I/O.
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// It returns an error, if any.
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func (file *File) Close() error {
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return file.file.close()
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}
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func (file *file) close() error {
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if file == nil || file.fd < 0 {
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return Ebadfd
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}
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var err error
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syscall.ForkLock.RLock()
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if e := syscall.Close(file.fd); e != nil {
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err = &PathError{"close", file.name, e}
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}
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syscall.ForkLock.RUnlock()
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file.fd = -1 // so it can't be closed again
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// no need for a finalizer anymore
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runtime.SetFinalizer(file, nil)
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return err
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}
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// Stat returns the FileInfo structure describing file.
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// It returns the FileInfo and an error, if any.
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func (f *File) Stat() (FileInfo, error) {
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d, err := dirstat(f)
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if err != nil {
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return nil, err
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}
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return fileInfoFromStat(d), nil
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}
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// Truncate changes the size of the file.
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// It does not change the I/O offset.
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func (f *File) Truncate(size int64) error {
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var d Dir
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d.Null()
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d.Length = uint64(size)
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if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {
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return &PathError{"truncate", f.name, e}
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}
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return nil
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}
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const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)
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// Chmod changes the mode of the file to mode.
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func (f *File) Chmod(mode FileMode) error {
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var d Dir
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odir, e := dirstat(f)
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if e != nil {
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return &PathError{"chmod", f.name, e}
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}
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d.Null()
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d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
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if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {
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return &PathError{"chmod", f.name, e}
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}
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return nil
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}
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// Sync commits the current contents of the file to stable storage.
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// Typically, this means flushing the file system's in-memory copy
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// of recently written data to disk.
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func (f *File) Sync() (err error) {
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if f == nil {
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return EINVAL
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}
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var d Dir
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d.Null()
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if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {
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return NewSyscallError("fsync", e)
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}
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return nil
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}
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// read reads up to len(b) bytes from the File.
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// It returns the number of bytes read and an error, if any.
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func (f *File) read(b []byte) (n int, err error) {
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return syscall.Read(f.fd, b)
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}
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// pread reads len(b) bytes from the File starting at byte offset off.
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// It returns the number of bytes read and the error, if any.
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// EOF is signaled by a zero count with err set to nil.
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func (f *File) pread(b []byte, off int64) (n int, err error) {
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return syscall.Pread(f.fd, b, off)
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}
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// write writes len(b) bytes to the File.
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// It returns the number of bytes written and an error, if any.
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func (f *File) write(b []byte) (n int, err error) {
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return syscall.Write(f.fd, b)
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}
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// pwrite writes len(b) bytes to the File starting at byte offset off.
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// It returns the number of bytes written and an error, if any.
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func (f *File) pwrite(b []byte, off int64) (n int, err error) {
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return syscall.Pwrite(f.fd, b, off)
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}
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// seek sets the offset for the next Read or Write on file to offset, interpreted
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// according to whence: 0 means relative to the origin of the file, 1 means
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// relative to the current offset, and 2 means relative to the end.
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// It returns the new offset and an error, if any.
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func (f *File) seek(offset int64, whence int) (ret int64, err error) {
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return syscall.Seek(f.fd, offset, whence)
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}
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// Truncate changes the size of the named file.
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// If the file is a symbolic link, it changes the size of the link's target.
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func Truncate(name string, size int64) error {
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var d Dir
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d.Null()
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d.Length = uint64(size)
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if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {
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return &PathError{"truncate", name, e}
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}
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return nil
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}
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// Remove removes the named file or directory.
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func Remove(name string) error {
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if e := syscall.Remove(name); e != nil {
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return &PathError{"remove", name, e}
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}
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return nil
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}
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// Rename renames a file.
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func Rename(oldname, newname string) error {
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var d Dir
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d.Null()
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d.Name = newname
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if e := syscall.Wstat(oldname, pdir(nil, &d)); e != nil {
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return &PathError{"rename", oldname, e}
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}
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return nil
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}
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// Chmod changes the mode of the named file to mode.
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func Chmod(name string, mode FileMode) error {
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var d Dir
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odir, e := dirstat(name)
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if e != nil {
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return &PathError{"chmod", name, e}
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}
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d.Null()
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d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
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if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {
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return &PathError{"chmod", name, e}
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}
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return nil
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}
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// Chtimes changes the access and modification times of the named
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// file, similar to the Unix utime() or utimes() functions.
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//
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// The underlying filesystem may truncate or round the values to a
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// less precise time unit.
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func Chtimes(name string, atime time.Time, mtime time.Time) error {
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var d Dir
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d.Null()
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d.Atime = uint32(atime.Unix())
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d.Mtime = uint32(mtime.Unix())
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if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {
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return &PathError{"chtimes", name, e}
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}
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return nil
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}
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func Pipe() (r *File, w *File, err error) {
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var p [2]int
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syscall.ForkLock.RLock()
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if e := syscall.Pipe(p[0:]); e != nil {
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syscall.ForkLock.RUnlock()
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return nil, nil, NewSyscallError("pipe", e)
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}
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syscall.ForkLock.RUnlock()
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return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
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}
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// not supported on Plan 9
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// Link creates a hard link.
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func Link(oldname, newname string) error {
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return EPLAN9
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}
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func Symlink(oldname, newname string) error {
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return EPLAN9
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}
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func Readlink(name string) (string, error) {
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return "", EPLAN9
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}
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func Chown(name string, uid, gid int) error {
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return EPLAN9
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}
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func Lchown(name string, uid, gid int) error {
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return EPLAN9
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}
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func (f *File) Chown(uid, gid int) error {
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return EPLAN9
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}
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// TempDir returns the default directory to use for temporary files.
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func TempDir() string {
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return "/tmp"
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}
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