libgo/go/os/file_posix.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build aix darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
   6
   7 package os
   8
   9 import (
  10         "syscall"
  11         "time"
  12 )
  13
  14 func sigpipe() // implemented in package runtime
  15
  16 // Readlink returns the destination of the named symbolic link.
  17 // If there is an error, it will be of type *PathError.
  18 func Readlink(name string) (string, error) {
  19         for len := 128; ; len *= 2 {
  20                 b := make([]byte, len)
  21                 n, e := fixCount(syscall.Readlink(fixLongPath(name), b))
  22                 // buffer too small
  23                 if e == syscall.ERANGE {
  24                         continue
  25                 }
  26                 if e != nil {
  27                         return "", &PathError{"readlink", name, e}
  28                 }
  29                 if n < len {
  30                         return string(b[0:n]), nil
  31                 }
  32         }
  33 }
  34
  35 // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
  36 func syscallMode(i FileMode) (o uint32) {
  37         o |= uint32(i.Perm())
  38         if i&ModeSetuid != 0 {
  39                 o |= syscall.S_ISUID
  40         }
  41         if i&ModeSetgid != 0 {
  42                 o |= syscall.S_ISGID
  43         }
  44         if i&ModeSticky != 0 {
  45                 o |= syscall.S_ISVTX
  46         }
  47         // No mapping for Go's ModeTemporary (plan9 only).
  48         return
  49 }
  50
  51 // Chmod changes the mode of the named file to mode.
  52 // If the file is a symbolic link, it changes the mode of the link's target.
  53 // If there is an error, it will be of type *PathError.
  54 func Chmod(name string, mode FileMode) error {
  55         if e := syscall.Chmod(name, syscallMode(mode)); e != nil {
  56                 return &PathError{"chmod", name, e}
  57         }
  58         return nil
  59 }
  60
  61 // Chmod changes the mode of the file to mode.
  62 // If there is an error, it will be of type *PathError.
  63 func (f *File) Chmod(mode FileMode) error {
  64         if err := f.checkValid("chmod"); err != nil {
  65                 return err
  66         }
  67         if e := syscall.Fchmod(f.fd, syscallMode(mode)); e != nil {
  68                 return &PathError{"chmod", f.name, e}
  69         }
  70         return nil
  71 }
  72
  73 // Chown changes the numeric uid and gid of the named file.
  74 // If the file is a symbolic link, it changes the uid and gid of the link's target.
  75 // If there is an error, it will be of type *PathError.
  76 func Chown(name string, uid, gid int) error {
  77         if e := syscall.Chown(name, uid, gid); e != nil {
  78                 return &PathError{"chown", name, e}
  79         }
  80         return nil
  81 }
  82
  83 // Lchown changes the numeric uid and gid of the named file.
  84 // If the file is a symbolic link, it changes the uid and gid of the link itself.
  85 // If there is an error, it will be of type *PathError.
  86 func Lchown(name string, uid, gid int) error {
  87         if e := syscall.Lchown(name, uid, gid); e != nil {
  88                 return &PathError{"lchown", name, e}
  89         }
  90         return nil
  91 }
  92
  93 // Chown changes the numeric uid and gid of the named file.
  94 // If there is an error, it will be of type *PathError.
  95 func (f *File) Chown(uid, gid int) error {
  96         if err := f.checkValid("chown"); err != nil {
  97                 return err
  98         }
  99         if e := syscall.Fchown(f.fd, uid, gid); e != nil {
 100                 return &PathError{"chown", f.name, e}
 101         }
 102         return nil
 103 }
 104
 105 // Truncate changes the size of the file.
 106 // It does not change the I/O offset.
 107 // If there is an error, it will be of type *PathError.
 108 func (f *File) Truncate(size int64) error {
 109         if err := f.checkValid("truncate"); err != nil {
 110                 return err
 111         }
 112         if e := syscall.Ftruncate(f.fd, size); e != nil {
 113                 return &PathError{"truncate", f.name, e}
 114         }
 115         return nil
 116 }
 117
 118 // Sync commits the current contents of the file to stable storage.
 119 // Typically, this means flushing the file system's in-memory copy
 120 // of recently written data to disk.
 121 func (f *File) Sync() error {
 122         if err := f.checkValid("sync"); err != nil {
 123                 return err
 124         }
 125         if e := syscall.Fsync(f.fd); e != nil {
 126                 return &PathError{"sync", f.name, e}
 127         }
 128         return nil
 129 }
 130
 131 // Chtimes changes the access and modification times of the named
 132 // file, similar to the Unix utime() or utimes() functions.
 133 //
 134 // The underlying filesystem may truncate or round the values to a
 135 // less precise time unit.
 136 // If there is an error, it will be of type *PathError.
 137 func Chtimes(name string, atime time.Time, mtime time.Time) error {
 138         var utimes [2]syscall.Timespec
 139         utimes[0] = syscall.NsecToTimespec(atime.UnixNano())
 140         utimes[1] = syscall.NsecToTimespec(mtime.UnixNano())
 141         if e := syscall.UtimesNano(fixLongPath(name), utimes[0:]); e != nil {
 142                 return &PathError{"chtimes", name, e}
 143         }
 144         return nil
 145 }