1// Copyright 2011 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 5package os 6 7import ( 8 "runtime" 9 "syscall" 10 "time" 11) 12 13// File represents an open file descriptor. 14type File struct { 15 *file 16} 17 18// file is the real representation of *File. 19// The extra level of indirection ensures that no clients of os 20// can overwrite this data, which could cause the finalizer 21// to close the wrong file descriptor. 22type file struct { 23 fd int 24 name string 25 dirinfo *dirInfo // nil unless directory being read 26} 27 28// Fd returns the integer Plan 9 file descriptor referencing the open file. 29// The file descriptor is valid only until f.Close is called or f is garbage collected. 30func (f *File) Fd() uintptr { 31 if f == nil { 32 return ^(uintptr(0)) 33 } 34 return uintptr(f.fd) 35} 36 37// NewFile returns a new File with the given file descriptor and name. 38func NewFile(fd uintptr, name string) *File { 39 fdi := int(fd) 40 if fdi < 0 { 41 return nil 42 } 43 f := &File{&file{fd: fdi, name: name}} 44 runtime.SetFinalizer(f.file, (*file).close) 45 return f 46} 47 48// Auxiliary information if the File describes a directory 49type dirInfo struct { 50 buf [syscall.STATMAX]byte // buffer for directory I/O 51 nbuf int // length of buf; return value from Read 52 bufp int // location of next record in buf. 53} 54 55func epipecheck(file *File, e error) { 56} 57 58// DevNull is the name of the operating system's ``null device.'' 59// On Unix-like systems, it is "/dev/null"; on Windows, "NUL". 60const DevNull = "/dev/null" 61 62// syscallMode returns the syscall-specific mode bits from Go's portable mode bits. 63func syscallMode(i FileMode) (o uint32) { 64 o |= uint32(i.Perm()) 65 if i&ModeAppend != 0 { 66 o |= syscall.DMAPPEND 67 } 68 if i&ModeExclusive != 0 { 69 o |= syscall.DMEXCL 70 } 71 if i&ModeTemporary != 0 { 72 o |= syscall.DMTMP 73 } 74 return 75} 76 77// OpenFile is the generalized open call; most users will use Open 78// or Create instead. It opens the named file with specified flag 79// (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful, 80// methods on the returned File can be used for I/O. 81// If there is an error, it will be of type *PathError. 82func OpenFile(name string, flag int, perm FileMode) (*File, error) { 83 var ( 84 fd int 85 e error 86 create bool 87 excl bool 88 trunc bool 89 append bool 90 ) 91 92 if flag&O_CREATE == O_CREATE { 93 flag = flag & ^O_CREATE 94 create = true 95 } 96 if flag&O_EXCL == O_EXCL { 97 excl = true 98 } 99 if flag&O_TRUNC == O_TRUNC { 100 trunc = true 101 } 102 // O_APPEND is emulated on Plan 9 103 if flag&O_APPEND == O_APPEND { 104 flag = flag &^ O_APPEND 105 append = true 106 } 107 108 if (create && trunc) || excl { 109 fd, e = syscall.Create(name, flag, syscallMode(perm)) 110 } else { 111 fd, e = syscall.Open(name, flag) 112 if e != nil && create { 113 var e1 error 114 fd, e1 = syscall.Create(name, flag, syscallMode(perm)) 115 if e1 == nil { 116 e = nil 117 } 118 } 119 } 120 121 if e != nil { 122 return nil, &PathError{"open", name, e} 123 } 124 125 if append { 126 if _, e = syscall.Seek(fd, 0, SEEK_END); e != nil { 127 return nil, &PathError{"seek", name, e} 128 } 129 } 130 131 return NewFile(uintptr(fd), name), nil 132} 133 134// Close closes the File, rendering it unusable for I/O. 135// It returns an error, if any. 136func (f *File) Close() error { 137 if f == nil { 138 return ErrInvalid 139 } 140 return f.file.close() 141} 142 143func (file *file) close() error { 144 if file == nil || file.fd < 0 { 145 return ErrInvalid 146 } 147 var err error 148 syscall.ForkLock.RLock() 149 if e := syscall.Close(file.fd); e != nil { 150 err = &PathError{"close", file.name, e} 151 } 152 syscall.ForkLock.RUnlock() 153 file.fd = -1 // so it can't be closed again 154 155 // no need for a finalizer anymore 156 runtime.SetFinalizer(file, nil) 157 return err 158} 159 160// Stat returns the FileInfo structure describing file. 161// If there is an error, it will be of type *PathError. 162func (f *File) Stat() (FileInfo, error) { 163 if f == nil { 164 return nil, ErrInvalid 165 } 166 d, err := dirstat(f) 167 if err != nil { 168 return nil, err 169 } 170 return fileInfoFromStat(d), nil 171} 172 173// Truncate changes the size of the file. 174// It does not change the I/O offset. 175// If there is an error, it will be of type *PathError. 176func (f *File) Truncate(size int64) error { 177 if f == nil { 178 return ErrInvalid 179 } 180 181 var d syscall.Dir 182 d.Null() 183 d.Length = size 184 185 var buf [syscall.STATFIXLEN]byte 186 n, err := d.Marshal(buf[:]) 187 if err != nil { 188 return &PathError{"truncate", f.name, err} 189 } 190 if err = syscall.Fwstat(f.fd, buf[:n]); err != nil { 191 return &PathError{"truncate", f.name, err} 192 } 193 return nil 194} 195 196const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm) 197 198// Chmod changes the mode of the file to mode. 199// If there is an error, it will be of type *PathError. 200func (f *File) Chmod(mode FileMode) error { 201 if f == nil { 202 return ErrInvalid 203 } 204 var d syscall.Dir 205 206 odir, e := dirstat(f) 207 if e != nil { 208 return &PathError{"chmod", f.name, e} 209 } 210 d.Null() 211 d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask 212 213 var buf [syscall.STATFIXLEN]byte 214 n, err := d.Marshal(buf[:]) 215 if err != nil { 216 return &PathError{"chmod", f.name, err} 217 } 218 if err = syscall.Fwstat(f.fd, buf[:n]); err != nil { 219 return &PathError{"chmod", f.name, err} 220 } 221 return nil 222} 223 224// Sync commits the current contents of the file to stable storage. 225// Typically, this means flushing the file system's in-memory copy 226// of recently written data to disk. 227func (f *File) Sync() error { 228 if f == nil { 229 return ErrInvalid 230 } 231 var d syscall.Dir 232 d.Null() 233 234 var buf [syscall.STATFIXLEN]byte 235 n, err := d.Marshal(buf[:]) 236 if err != nil { 237 return NewSyscallError("fsync", err) 238 } 239 if err = syscall.Fwstat(f.fd, buf[:n]); err != nil { 240 return NewSyscallError("fsync", err) 241 } 242 return nil 243} 244 245// read reads up to len(b) bytes from the File. 246// It returns the number of bytes read and an error, if any. 247func (f *File) read(b []byte) (n int, err error) { 248 return fixCount(syscall.Read(f.fd, b)) 249} 250 251// pread reads len(b) bytes from the File starting at byte offset off. 252// It returns the number of bytes read and the error, if any. 253// EOF is signaled by a zero count with err set to nil. 254func (f *File) pread(b []byte, off int64) (n int, err error) { 255 return fixCount(syscall.Pread(f.fd, b, off)) 256} 257 258// write writes len(b) bytes to the File. 259// It returns the number of bytes written and an error, if any. 260// Since Plan 9 preserves message boundaries, never allow 261// a zero-byte write. 262func (f *File) write(b []byte) (n int, err error) { 263 if len(b) == 0 { 264 return 0, nil 265 } 266 return fixCount(syscall.Write(f.fd, b)) 267} 268 269// pwrite writes len(b) bytes to the File starting at byte offset off. 270// It returns the number of bytes written and an error, if any. 271// Since Plan 9 preserves message boundaries, never allow 272// a zero-byte write. 273func (f *File) pwrite(b []byte, off int64) (n int, err error) { 274 if len(b) == 0 { 275 return 0, nil 276 } 277 return fixCount(syscall.Pwrite(f.fd, b, off)) 278} 279 280// seek sets the offset for the next Read or Write on file to offset, interpreted 281// according to whence: 0 means relative to the origin of the file, 1 means 282// relative to the current offset, and 2 means relative to the end. 283// It returns the new offset and an error, if any. 284func (f *File) seek(offset int64, whence int) (ret int64, err error) { 285 return syscall.Seek(f.fd, offset, whence) 286} 287 288// Truncate changes the size of the named file. 289// If the file is a symbolic link, it changes the size of the link's target. 290// If there is an error, it will be of type *PathError. 291func Truncate(name string, size int64) error { 292 var d syscall.Dir 293 294 d.Null() 295 d.Length = size 296 297 var buf [syscall.STATFIXLEN]byte 298 n, err := d.Marshal(buf[:]) 299 if err != nil { 300 return &PathError{"truncate", name, err} 301 } 302 if err = syscall.Wstat(name, buf[:n]); err != nil { 303 return &PathError{"truncate", name, err} 304 } 305 return nil 306} 307 308// Remove removes the named file or directory. 309// If there is an error, it will be of type *PathError. 310func Remove(name string) error { 311 if e := syscall.Remove(name); e != nil { 312 return &PathError{"remove", name, e} 313 } 314 return nil 315} 316 317// HasPrefix from the strings package. 318func hasPrefix(s, prefix string) bool { 319 return len(s) >= len(prefix) && s[0:len(prefix)] == prefix 320} 321 322// LastIndexByte from the strings package. 323func lastIndex(s string, sep byte) int { 324 for i := len(s) - 1; i >= 0; i-- { 325 if s[i] == sep { 326 return i 327 } 328 } 329 return -1 330} 331 332func rename(oldname, newname string) error { 333 dirname := oldname[:lastIndex(oldname, '/')+1] 334 if hasPrefix(newname, dirname) { 335 newname = newname[len(dirname):] 336 } else { 337 return &LinkError{"rename", oldname, newname, ErrInvalid} 338 } 339 340 // If newname still contains slashes after removing the oldname 341 // prefix, the rename is cross-directory and must be rejected. 342 if lastIndex(newname, '/') >= 0 { 343 return &LinkError{"rename", oldname, newname, ErrInvalid} 344 } 345 346 var d syscall.Dir 347 348 d.Null() 349 d.Name = newname 350 351 buf := make([]byte, syscall.STATFIXLEN+len(d.Name)) 352 n, err := d.Marshal(buf[:]) 353 if err != nil { 354 return &LinkError{"rename", oldname, newname, err} 355 } 356 357 // If newname already exists and is not a directory, rename replaces it. 358 f, err := Stat(dirname + newname) 359 if err == nil && !f.IsDir() { 360 Remove(dirname + newname) 361 } 362 363 if err = syscall.Wstat(oldname, buf[:n]); err != nil { 364 return &LinkError{"rename", oldname, newname, err} 365 } 366 return nil 367} 368 369// Chmod changes the mode of the named file to mode. 370// If the file is a symbolic link, it changes the mode of the link's target. 371// If there is an error, it will be of type *PathError. 372func Chmod(name string, mode FileMode) error { 373 var d syscall.Dir 374 375 odir, e := dirstat(name) 376 if e != nil { 377 return &PathError{"chmod", name, e} 378 } 379 d.Null() 380 d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask 381 382 var buf [syscall.STATFIXLEN]byte 383 n, err := d.Marshal(buf[:]) 384 if err != nil { 385 return &PathError{"chmod", name, err} 386 } 387 if err = syscall.Wstat(name, buf[:n]); err != nil { 388 return &PathError{"chmod", name, err} 389 } 390 return nil 391} 392 393// Chtimes changes the access and modification times of the named 394// file, similar to the Unix utime() or utimes() functions. 395// 396// The underlying filesystem may truncate or round the values to a 397// less precise time unit. 398// If there is an error, it will be of type *PathError. 399func Chtimes(name string, atime time.Time, mtime time.Time) error { 400 var d syscall.Dir 401 402 d.Null() 403 d.Atime = uint32(atime.Unix()) 404 d.Mtime = uint32(mtime.Unix()) 405 406 var buf [syscall.STATFIXLEN]byte 407 n, err := d.Marshal(buf[:]) 408 if err != nil { 409 return &PathError{"chtimes", name, err} 410 } 411 if err = syscall.Wstat(name, buf[:n]); err != nil { 412 return &PathError{"chtimes", name, err} 413 } 414 return nil 415} 416 417// Pipe returns a connected pair of Files; reads from r return bytes 418// written to w. It returns the files and an error, if any. 419func Pipe() (r *File, w *File, err error) { 420 var p [2]int 421 422 syscall.ForkLock.RLock() 423 if e := syscall.Pipe(p[0:]); e != nil { 424 syscall.ForkLock.RUnlock() 425 return nil, nil, NewSyscallError("pipe", e) 426 } 427 syscall.ForkLock.RUnlock() 428 429 return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil 430} 431 432// not supported on Plan 9 433 434// Link creates newname as a hard link to the oldname file. 435// If there is an error, it will be of type *LinkError. 436func Link(oldname, newname string) error { 437 return &LinkError{"link", oldname, newname, syscall.EPLAN9} 438} 439 440// Symlink creates newname as a symbolic link to oldname. 441// If there is an error, it will be of type *LinkError. 442func Symlink(oldname, newname string) error { 443 return &LinkError{"symlink", oldname, newname, syscall.EPLAN9} 444} 445 446// Readlink returns the destination of the named symbolic link. 447// If there is an error, it will be of type *PathError. 448func Readlink(name string) (string, error) { 449 return "", &PathError{"readlink", name, syscall.EPLAN9} 450} 451 452// Chown changes the numeric uid and gid of the named file. 453// If the file is a symbolic link, it changes the uid and gid of the link's target. 454// If there is an error, it will be of type *PathError. 455func Chown(name string, uid, gid int) error { 456 return &PathError{"chown", name, syscall.EPLAN9} 457} 458 459// Lchown changes the numeric uid and gid of the named file. 460// If the file is a symbolic link, it changes the uid and gid of the link itself. 461// If there is an error, it will be of type *PathError. 462func Lchown(name string, uid, gid int) error { 463 return &PathError{"lchown", name, syscall.EPLAN9} 464} 465 466// Chown changes the numeric uid and gid of the named file. 467// If there is an error, it will be of type *PathError. 468func (f *File) Chown(uid, gid int) error { 469 if f == nil { 470 return ErrInvalid 471 } 472 return &PathError{"chown", f.name, syscall.EPLAN9} 473} 474 475// TempDir returns the default directory to use for temporary files. 476func TempDir() string { 477 return "/tmp" 478} 479