Source file src/os/file_plan9.go

Documentation: os

     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  
     5  package os
     6  
     7  import (
     8  	"internal/poll"
     9  	"io"
    10  	"runtime"
    11  	"syscall"
    12  	"time"
    13  )
    14  
    15  // fixLongPath is a noop on non-Windows platforms.
    16  func fixLongPath(path string) string {
    17  	return path
    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  }
    29  
    30  // Fd returns the integer Plan 9 file descriptor referencing the open file.
    31  // The file descriptor is valid only until f.Close is called or f is garbage collected.
    32  // On Unix systems this will cause the SetDeadline methods to stop working.
    33  func (f *File) Fd() uintptr {
    34  	if f == nil {
    35  		return ^(uintptr(0))
    36  	}
    37  	return uintptr(f.fd)
    38  }
    39  
    40  // NewFile returns a new File with the given file descriptor and
    41  // name. The returned value will be nil if fd is not a valid file
    42  // descriptor.
    43  func NewFile(fd uintptr, name string) *File {
    44  	fdi := int(fd)
    45  	if fdi < 0 {
    46  		return nil
    47  	}
    48  	f := &File{&file{fd: fdi, name: name}}
    49  	runtime.SetFinalizer(f.file, (*file).close)
    50  	return f
    51  }
    52  
    53  // Auxiliary information if the File describes a directory
    54  type dirInfo struct {
    55  	buf  [syscall.STATMAX]byte // buffer for directory I/O
    56  	nbuf int                   // length of buf; return value from Read
    57  	bufp int                   // location of next record in buf.
    58  }
    59  
    60  func epipecheck(file *File, e error) {
    61  }
    62  
    63  // DevNull is the name of the operating system's ``null device.''
    64  // On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
    65  const DevNull = "/dev/null"
    66  
    67  // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
    68  func syscallMode(i FileMode) (o uint32) {
    69  	o |= uint32(i.Perm())
    70  	if i&ModeAppend != 0 {
    71  		o |= syscall.DMAPPEND
    72  	}
    73  	if i&ModeExclusive != 0 {
    74  		o |= syscall.DMEXCL
    75  	}
    76  	if i&ModeTemporary != 0 {
    77  		o |= syscall.DMTMP
    78  	}
    79  	return
    80  }
    81  
    82  // openFileNolog is the Plan 9 implementation of OpenFile.
    83  func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
    84  	var (
    85  		fd     int
    86  		e      error
    87  		create bool
    88  		excl   bool
    89  		trunc  bool
    90  		append bool
    91  	)
    92  
    93  	if flag&O_CREATE == O_CREATE {
    94  		flag = flag & ^O_CREATE
    95  		create = true
    96  	}
    97  	if flag&O_EXCL == O_EXCL {
    98  		excl = true
    99  	}
   100  	if flag&O_TRUNC == O_TRUNC {
   101  		trunc = true
   102  	}
   103  	// O_APPEND is emulated on Plan 9
   104  	if flag&O_APPEND == O_APPEND {
   105  		flag = flag &^ O_APPEND
   106  		append = true
   107  	}
   108  
   109  	if (create && trunc) || excl {
   110  		fd, e = syscall.Create(name, flag, syscallMode(perm))
   111  	} else {
   112  		fd, e = syscall.Open(name, flag)
   113  		if e != nil && create {
   114  			var e1 error
   115  			fd, e1 = syscall.Create(name, flag, syscallMode(perm))
   116  			if e1 == nil {
   117  				e = nil
   118  			}
   119  		}
   120  	}
   121  
   122  	if e != nil {
   123  		return nil, &PathError{"open", name, e}
   124  	}
   125  
   126  	if append {
   127  		if _, e = syscall.Seek(fd, 0, io.SeekEnd); e != nil {
   128  			return nil, &PathError{"seek", name, e}
   129  		}
   130  	}
   131  
   132  	return NewFile(uintptr(fd), name), nil
   133  }
   134  
   135  // Close closes the File, rendering it unusable for I/O.
   136  // On files that support SetDeadline, any pending I/O operations will
   137  // be canceled and return immediately with an error.
   138  func (f *File) Close() error {
   139  	if err := f.checkValid("close"); err != nil {
   140  		return err
   141  	}
   142  	return f.file.close()
   143  }
   144  
   145  func (file *file) close() error {
   146  	if file == nil || file.fd == badFd {
   147  		return ErrInvalid
   148  	}
   149  	var err error
   150  	if e := syscall.Close(file.fd); e != nil {
   151  		err = &PathError{"close", file.name, e}
   152  	}
   153  	file.fd = badFd // 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.
   162  func (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.
   176  func (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  
   196  const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)
   197  
   198  func (f *File) chmod(mode FileMode) error {
   199  	if f == nil {
   200  		return ErrInvalid
   201  	}
   202  	var d syscall.Dir
   203  
   204  	odir, e := dirstat(f)
   205  	if e != nil {
   206  		return &PathError{"chmod", f.name, e}
   207  	}
   208  	d.Null()
   209  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
   210  
   211  	var buf [syscall.STATFIXLEN]byte
   212  	n, err := d.Marshal(buf[:])
   213  	if err != nil {
   214  		return &PathError{"chmod", f.name, err}
   215  	}
   216  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
   217  		return &PathError{"chmod", f.name, err}
   218  	}
   219  	return nil
   220  }
   221  
   222  // Sync commits the current contents of the file to stable storage.
   223  // Typically, this means flushing the file system's in-memory copy
   224  // of recently written data to disk.
   225  func (f *File) Sync() error {
   226  	if f == nil {
   227  		return ErrInvalid
   228  	}
   229  	var d syscall.Dir
   230  	d.Null()
   231  
   232  	var buf [syscall.STATFIXLEN]byte
   233  	n, err := d.Marshal(buf[:])
   234  	if err != nil {
   235  		return NewSyscallError("fsync", err)
   236  	}
   237  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
   238  		return NewSyscallError("fsync", err)
   239  	}
   240  	return nil
   241  }
   242  
   243  // read reads up to len(b) bytes from the File.
   244  // It returns the number of bytes read and an error, if any.
   245  func (f *File) read(b []byte) (n int, err error) {
   246  	n, e := fixCount(syscall.Read(f.fd, b))
   247  	if n == 0 && len(b) > 0 && e == nil {
   248  		return 0, io.EOF
   249  	}
   250  	return n, e
   251  }
   252  
   253  // pread reads len(b) bytes from the File starting at byte offset off.
   254  // It returns the number of bytes read and the error, if any.
   255  // EOF is signaled by a zero count with err set to nil.
   256  func (f *File) pread(b []byte, off int64) (n int, err error) {
   257  	n, e := fixCount(syscall.Pread(f.fd, b, off))
   258  	if n == 0 && len(b) > 0 && e == nil {
   259  		return 0, io.EOF
   260  	}
   261  	return n, e
   262  }
   263  
   264  // write writes len(b) bytes to the File.
   265  // It returns the number of bytes written and an error, if any.
   266  // Since Plan 9 preserves message boundaries, never allow
   267  // a zero-byte write.
   268  func (f *File) write(b []byte) (n int, err error) {
   269  	if len(b) == 0 {
   270  		return 0, nil
   271  	}
   272  	return fixCount(syscall.Write(f.fd, b))
   273  }
   274  
   275  // pwrite writes len(b) bytes to the File starting at byte offset off.
   276  // It returns the number of bytes written and an error, if any.
   277  // Since Plan 9 preserves message boundaries, never allow
   278  // a zero-byte write.
   279  func (f *File) pwrite(b []byte, off int64) (n int, err error) {
   280  	if len(b) == 0 {
   281  		return 0, nil
   282  	}
   283  	return fixCount(syscall.Pwrite(f.fd, b, off))
   284  }
   285  
   286  // seek sets the offset for the next Read or Write on file to offset, interpreted
   287  // according to whence: 0 means relative to the origin of the file, 1 means
   288  // relative to the current offset, and 2 means relative to the end.
   289  // It returns the new offset and an error, if any.
   290  func (f *File) seek(offset int64, whence int) (ret int64, err error) {
   291  	return syscall.Seek(f.fd, offset, whence)
   292  }
   293  
   294  // Truncate changes the size of the named file.
   295  // If the file is a symbolic link, it changes the size of the link's target.
   296  // If there is an error, it will be of type *PathError.
   297  func Truncate(name string, size int64) error {
   298  	var d syscall.Dir
   299  
   300  	d.Null()
   301  	d.Length = size
   302  
   303  	var buf [syscall.STATFIXLEN]byte
   304  	n, err := d.Marshal(buf[:])
   305  	if err != nil {
   306  		return &PathError{"truncate", name, err}
   307  	}
   308  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   309  		return &PathError{"truncate", name, err}
   310  	}
   311  	return nil
   312  }
   313  
   314  // Remove removes the named file or directory.
   315  // If there is an error, it will be of type *PathError.
   316  func Remove(name string) error {
   317  	if e := syscall.Remove(name); e != nil {
   318  		return &PathError{"remove", name, e}
   319  	}
   320  	return nil
   321  }
   322  
   323  // HasPrefix from the strings package.
   324  func hasPrefix(s, prefix string) bool {
   325  	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
   326  }
   327  
   328  // LastIndexByte from the strings package.
   329  func lastIndex(s string, sep byte) int {
   330  	for i := len(s) - 1; i >= 0; i-- {
   331  		if s[i] == sep {
   332  			return i
   333  		}
   334  	}
   335  	return -1
   336  }
   337  
   338  func rename(oldname, newname string) error {
   339  	dirname := oldname[:lastIndex(oldname, '/')+1]
   340  	if hasPrefix(newname, dirname) {
   341  		newname = newname[len(dirname):]
   342  	} else {
   343  		return &LinkError{"rename", oldname, newname, ErrInvalid}
   344  	}
   345  
   346  	// If newname still contains slashes after removing the oldname
   347  	// prefix, the rename is cross-directory and must be rejected.
   348  	if lastIndex(newname, '/') >= 0 {
   349  		return &LinkError{"rename", oldname, newname, ErrInvalid}
   350  	}
   351  
   352  	var d syscall.Dir
   353  
   354  	d.Null()
   355  	d.Name = newname
   356  
   357  	buf := make([]byte, syscall.STATFIXLEN+len(d.Name))
   358  	n, err := d.Marshal(buf[:])
   359  	if err != nil {
   360  		return &LinkError{"rename", oldname, newname, err}
   361  	}
   362  
   363  	// If newname already exists and is not a directory, rename replaces it.
   364  	f, err := Stat(dirname + newname)
   365  	if err == nil && !f.IsDir() {
   366  		Remove(dirname + newname)
   367  	}
   368  
   369  	if err = syscall.Wstat(oldname, buf[:n]); err != nil {
   370  		return &LinkError{"rename", oldname, newname, err}
   371  	}
   372  	return nil
   373  }
   374  
   375  // See docs in file.go:Chmod.
   376  func chmod(name string, mode FileMode) error {
   377  	var d syscall.Dir
   378  
   379  	odir, e := dirstat(name)
   380  	if e != nil {
   381  		return &PathError{"chmod", name, e}
   382  	}
   383  	d.Null()
   384  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
   385  
   386  	var buf [syscall.STATFIXLEN]byte
   387  	n, err := d.Marshal(buf[:])
   388  	if err != nil {
   389  		return &PathError{"chmod", name, err}
   390  	}
   391  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   392  		return &PathError{"chmod", name, err}
   393  	}
   394  	return nil
   395  }
   396  
   397  // Chtimes changes the access and modification times of the named
   398  // file, similar to the Unix utime() or utimes() functions.
   399  //
   400  // The underlying filesystem may truncate or round the values to a
   401  // less precise time unit.
   402  // If there is an error, it will be of type *PathError.
   403  func Chtimes(name string, atime time.Time, mtime time.Time) error {
   404  	var d syscall.Dir
   405  
   406  	d.Null()
   407  	d.Atime = uint32(atime.Unix())
   408  	d.Mtime = uint32(mtime.Unix())
   409  
   410  	var buf [syscall.STATFIXLEN]byte
   411  	n, err := d.Marshal(buf[:])
   412  	if err != nil {
   413  		return &PathError{"chtimes", name, err}
   414  	}
   415  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   416  		return &PathError{"chtimes", name, err}
   417  	}
   418  	return nil
   419  }
   420  
   421  // Pipe returns a connected pair of Files; reads from r return bytes
   422  // written to w. It returns the files and an error, if any.
   423  func Pipe() (r *File, w *File, err error) {
   424  	var p [2]int
   425  
   426  	if e := syscall.Pipe(p[0:]); e != nil {
   427  		return nil, nil, NewSyscallError("pipe", e)
   428  	}
   429  
   430  	return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil
   431  }
   432  
   433  // not supported on Plan 9
   434  
   435  // Link creates newname as a hard link to the oldname file.
   436  // If there is an error, it will be of type *LinkError.
   437  func Link(oldname, newname string) error {
   438  	return &LinkError{"link", oldname, newname, syscall.EPLAN9}
   439  }
   440  
   441  // Symlink creates newname as a symbolic link to oldname.
   442  // If there is an error, it will be of type *LinkError.
   443  func Symlink(oldname, newname string) error {
   444  	return &LinkError{"symlink", oldname, newname, syscall.EPLAN9}
   445  }
   446  
   447  // Readlink returns the destination of the named symbolic link.
   448  // If there is an error, it will be of type *PathError.
   449  func Readlink(name string) (string, error) {
   450  	return "", &PathError{"readlink", name, syscall.EPLAN9}
   451  }
   452  
   453  // Chown changes the numeric uid and gid of the named file.
   454  // If the file is a symbolic link, it changes the uid and gid of the link's target.
   455  // A uid or gid of -1 means to not change that value.
   456  // If there is an error, it will be of type *PathError.
   457  //
   458  // On Windows or Plan 9, Chown always returns the syscall.EWINDOWS or
   459  // EPLAN9 error, wrapped in *PathError.
   460  func Chown(name string, uid, gid int) error {
   461  	return &PathError{"chown", name, syscall.EPLAN9}
   462  }
   463  
   464  // Lchown changes the numeric uid and gid of the named file.
   465  // If the file is a symbolic link, it changes the uid and gid of the link itself.
   466  // If there is an error, it will be of type *PathError.
   467  func Lchown(name string, uid, gid int) error {
   468  	return &PathError{"lchown", name, syscall.EPLAN9}
   469  }
   470  
   471  // Chown changes the numeric uid and gid of the named file.
   472  // If there is an error, it will be of type *PathError.
   473  func (f *File) Chown(uid, gid int) error {
   474  	if f == nil {
   475  		return ErrInvalid
   476  	}
   477  	return &PathError{"chown", f.name, syscall.EPLAN9}
   478  }
   479  
   480  func tempDir() string {
   481  	dir := Getenv("TMPDIR")
   482  	if dir == "" {
   483  		dir = "/tmp"
   484  	}
   485  	return dir
   486  
   487  }
   488  
   489  // Chdir changes the current working directory to the file,
   490  // which must be a directory.
   491  // If there is an error, it will be of type *PathError.
   492  func (f *File) Chdir() error {
   493  	if err := f.checkValid("chdir"); err != nil {
   494  		return err
   495  	}
   496  	if e := syscall.Fchdir(f.fd); e != nil {
   497  		return &PathError{"chdir", f.name, e}
   498  	}
   499  	return nil
   500  }
   501  
   502  // setDeadline sets the read and write deadline.
   503  func (f *File) setDeadline(time.Time) error {
   504  	if err := f.checkValid("SetDeadline"); err != nil {
   505  		return err
   506  	}
   507  	return poll.ErrNoDeadline
   508  }
   509  
   510  // setReadDeadline sets the read deadline.
   511  func (f *File) setReadDeadline(time.Time) error {
   512  	if err := f.checkValid("SetReadDeadline"); err != nil {
   513  		return err
   514  	}
   515  	return poll.ErrNoDeadline
   516  }
   517  
   518  // setWriteDeadline sets the write deadline.
   519  func (f *File) setWriteDeadline(time.Time) error {
   520  	if err := f.checkValid("SetWriteDeadline"); err != nil {
   521  		return err
   522  	}
   523  	return poll.ErrNoDeadline
   524  }
   525  
   526  // checkValid checks whether f is valid for use.
   527  // If not, it returns an appropriate error, perhaps incorporating the operation name op.
   528  func (f *File) checkValid(op string) error {
   529  	if f == nil {
   530  		return ErrInvalid
   531  	}
   532  	if f.fd == badFd {
   533  		return &PathError{op, f.name, ErrClosed}
   534  	}
   535  	return nil
   536  }
   537  

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