libgo/go/os/file_unix.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 darwin dragonfly freebsd linux netbsd openbsd
   6
   7 package os
   8
   9 import (
  10         "runtime"
  11         "sync/atomic"
  12         "syscall"
  13 )
  14
  15 // File represents an open file descriptor.
  16 type File struct {
  17         *file
  18 }
  19
  20 // file is the real representation of *File.
  21 // The extra level of indirection ensures that no clients of os
  22 // can overwrite this data, which could cause the finalizer
  23 // to close the wrong file descriptor.
  24 type file struct {
  25         fd      int
  26         name    string
  27         dirinfo *dirInfo // nil unless directory being read
  28         nepipe  int32    // number of consecutive EPIPE in Write
  29 }
  30
  31 // Fd returns the integer Unix file descriptor referencing the open file.
  32 func (f *File) Fd() uintptr {
  33         if f == nil {
  34                 return ^(uintptr(0))
  35         }
  36         return uintptr(f.fd)
  37 }
  38
  39 // NewFile returns a new File with the given file descriptor and name.
  40 func NewFile(fd uintptr, name string) *File {
  41         fdi := int(fd)
  42         if fdi < 0 {
  43                 return nil
  44         }
  45         f := &File{&file{fd: fdi, name: name}}
  46         runtime.SetFinalizer(f.file, (*file).close)
  47         return f
  48 }
  49
  50 // Auxiliary information if the File describes a directory
  51 type dirInfo struct {
  52         buf []byte       // buffer for directory I/O
  53         dir *syscall.DIR // from opendir
  54 }
  55
  56 func epipecheck(file *File, e error) {
  57         if e == syscall.EPIPE {
  58                 if atomic.AddInt32(&file.nepipe, 1) >= 10 {
  59                         sigpipe()
  60                 }
  61         } else {
  62                 atomic.StoreInt32(&file.nepipe, 0)
  63         }
  64 }
  65
  66 // DevNull is the name of the operating system's ``null device.''
  67 // On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
  68 const DevNull = "/dev/null"
  69
  70 // OpenFile is the generalized open call; most users will use Open
  71 // or Create instead.  It opens the named file with specified flag
  72 // (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful,
  73 // methods on the returned File can be used for I/O.
  74 // If there is an error, it will be of type *PathError.
  75 func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {
  76         r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
  77         if e != nil {
  78                 return nil, &PathError{"open", name, e}
  79         }
  80
  81         // There's a race here with fork/exec, which we are
  82         // content to live with.  See ../syscall/exec_unix.go.
  83         // On OS X 10.6, the O_CLOEXEC flag is not respected.
  84         // On OS X 10.7, the O_CLOEXEC flag works.
  85         // Without a cheap & reliable way to detect 10.6 vs 10.7 at
  86         // runtime, we just always call syscall.CloseOnExec on Darwin.
  87         // Once >=10.7 is prevalent, this extra call can removed.
  88         if syscall.O_CLOEXEC == 0 || runtime.GOOS == "darwin" { // O_CLOEXEC not supported
  89                 syscall.CloseOnExec(r)
  90         }
  91
  92         return NewFile(uintptr(r), name), nil
  93 }
  94
  95 // Close closes the File, rendering it unusable for I/O.
  96 // It returns an error, if any.
  97 func (f *File) Close() error {
  98         if f == nil {
  99                 return ErrInvalid
 100         }
 101         return f.file.close()
 102 }
 103
 104 func (file *file) close() error {
 105         if file == nil || file.fd < 0 {
 106                 return syscall.EINVAL
 107         }
 108         var err error
 109         if e := syscall.Close(file.fd); e != nil {
 110                 err = &PathError{"close", file.name, e}
 111         }
 112
 113         if file.dirinfo != nil {
 114                 syscall.Entersyscall()
 115                 i := libc_closedir(file.dirinfo.dir)
 116                 errno := syscall.GetErrno()
 117                 syscall.Exitsyscall()
 118                 file.dirinfo = nil
 119                 if i < 0 && err == nil {
 120                         err = &PathError{"closedir", file.name, errno}
 121                 }
 122         }
 123
 124         file.fd = -1 // so it can't be closed again
 125
 126         // no need for a finalizer anymore
 127         runtime.SetFinalizer(file, nil)
 128         return err
 129 }
 130
 131 // Stat returns the FileInfo structure describing file.
 132 // If there is an error, it will be of type *PathError.
 133 func (f *File) Stat() (fi FileInfo, err error) {
 134         if f == nil {
 135                 return nil, ErrInvalid
 136         }
 137         var stat syscall.Stat_t
 138         err = syscall.Fstat(f.fd, &stat)
 139         if err != nil {
 140                 return nil, &PathError{"stat", f.name, err}
 141         }
 142         return fileInfoFromStat(&stat, f.name), nil
 143 }
 144
 145 // Stat returns a FileInfo describing the named file.
 146 // If there is an error, it will be of type *PathError.
 147 func Stat(name string) (fi FileInfo, err error) {
 148         var stat syscall.Stat_t
 149         err = syscall.Stat(name, &stat)
 150         if err != nil {
 151                 return nil, &PathError{"stat", name, err}
 152         }
 153         return fileInfoFromStat(&stat, name), nil
 154 }
 155
 156 // Lstat returns a FileInfo describing the named file.
 157 // If the file is a symbolic link, the returned FileInfo
 158 // describes the symbolic link.  Lstat makes no attempt to follow the link.
 159 // If there is an error, it will be of type *PathError.
 160 func Lstat(name string) (fi FileInfo, err error) {
 161         var stat syscall.Stat_t
 162         err = syscall.Lstat(name, &stat)
 163         if err != nil {
 164                 return nil, &PathError{"lstat", name, err}
 165         }
 166         return fileInfoFromStat(&stat, name), nil
 167 }
 168
 169 func (f *File) readdir(n int) (fi []FileInfo, err error) {
 170         dirname := f.name
 171         if dirname == "" {
 172                 dirname = "."
 173         }
 174         dirname += "/"
 175         names, err := f.Readdirnames(n)
 176         fi = make([]FileInfo, len(names))
 177         for i, filename := range names {
 178                 fip, lerr := lstat(dirname + filename)
 179                 if lerr != nil {
 180                         fi[i] = &fileStat{name: filename}
 181                         continue
 182                 }
 183                 fi[i] = fip
 184         }
 185         return fi, err
 186 }
 187
 188 // read reads up to len(b) bytes from the File.
 189 // It returns the number of bytes read and an error, if any.
 190 func (f *File) read(b []byte) (n int, err error) {
 191         return syscall.Read(f.fd, b)
 192 }
 193
 194 // pread reads len(b) bytes from the File starting at byte offset off.
 195 // It returns the number of bytes read and the error, if any.
 196 // EOF is signaled by a zero count with err set to 0.
 197 func (f *File) pread(b []byte, off int64) (n int, err error) {
 198         return syscall.Pread(f.fd, b, off)
 199 }
 200
 201 // write writes len(b) bytes to the File.
 202 // It returns the number of bytes written and an error, if any.
 203 func (f *File) write(b []byte) (n int, err error) {
 204         for {
 205                 m, err := syscall.Write(f.fd, b)
 206                 n += m
 207
 208                 // If the syscall wrote some data but not all (short write)
 209                 // or it returned EINTR, then assume it stopped early for
 210                 // reasons that are uninteresting to the caller, and try again.
 211                 if 0 < m && m < len(b) || err == syscall.EINTR {
 212                         b = b[m:]
 213                         continue
 214                 }
 215
 216                 return n, err
 217         }
 218 }
 219
 220 // pwrite writes len(b) bytes to the File starting at byte offset off.
 221 // It returns the number of bytes written and an error, if any.
 222 func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 223         return syscall.Pwrite(f.fd, b, off)
 224 }
 225
 226 // seek sets the offset for the next Read or Write on file to offset, interpreted
 227 // according to whence: 0 means relative to the origin of the file, 1 means
 228 // relative to the current offset, and 2 means relative to the end.
 229 // It returns the new offset and an error, if any.
 230 func (f *File) seek(offset int64, whence int) (ret int64, err error) {
 231         return syscall.Seek(f.fd, offset, whence)
 232 }
 233
 234 // Truncate changes the size of the named file.
 235 // If the file is a symbolic link, it changes the size of the link's target.
 236 // If there is an error, it will be of type *PathError.
 237 func Truncate(name string, size int64) error {
 238         if e := syscall.Truncate(name, size); e != nil {
 239                 return &PathError{"truncate", name, e}
 240         }
 241         return nil
 242 }
 243
 244 // Remove removes the named file or directory.
 245 // If there is an error, it will be of type *PathError.
 246 func Remove(name string) error {
 247         // System call interface forces us to know
 248         // whether name is a file or directory.
 249         // Try both: it is cheaper on average than
 250         // doing a Stat plus the right one.
 251         e := syscall.Unlink(name)
 252         if e == nil {
 253                 return nil
 254         }
 255         e1 := syscall.Rmdir(name)
 256         if e1 == nil {
 257                 return nil
 258         }
 259
 260         // Both failed: figure out which error to return.
 261         // OS X and Linux differ on whether unlink(dir)
 262         // returns EISDIR, so can't use that.  However,
 263         // both agree that rmdir(file) returns ENOTDIR,
 264         // so we can use that to decide which error is real.
 265         // Rmdir might also return ENOTDIR if given a bad
 266         // file path, like /etc/passwd/foo, but in that case,
 267         // both errors will be ENOTDIR, so it's okay to
 268         // use the error from unlink.
 269         if e1 != syscall.ENOTDIR {
 270                 e = e1
 271         }
 272         return &PathError{"remove", name, e}
 273 }
 274
 275 // basename removes trailing slashes and the leading directory name from path name
 276 func basename(name string) string {
 277         i := len(name) - 1
 278         // Remove trailing slashes
 279         for ; i > 0 && name[i] == '/'; i-- {
 280                 name = name[:i]
 281         }
 282         // Remove leading directory name
 283         for i--; i >= 0; i-- {
 284                 if name[i] == '/' {
 285                         name = name[i+1:]
 286                         break
 287                 }
 288         }
 289
 290         return name
 291 }
 292
 293 // TempDir returns the default directory to use for temporary files.
 294 func TempDir() string {
 295         dir := Getenv("TMPDIR")
 296         if dir == "" {
 297                 dir = "/tmp"
 298         }
 299         return dir
 300 }