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  	appendMode bool     // whether file is opened for appending
    29  }
    30  
    31  // Fd returns the integer Plan 9 file descriptor referencing the open file.
    32  // The file descriptor is valid only until f.Close is called or f is garbage collected.
    33  // On Unix systems this will cause the SetDeadline methods to stop working.
    34  func (f *File) Fd() uintptr {
    35  	if f == nil {
    36  		return ^(uintptr(0))
    37  	}
    38  	return uintptr(f.fd)
    39  }
    40  
    41  // NewFile returns a new File with the given file descriptor and
    42  // name. The returned value will be nil if fd is not a valid file
    43  // descriptor.
    44  func NewFile(fd uintptr, name string) *File {
    45  	fdi := int(fd)
    46  	if fdi < 0 {
    47  		return nil
    48  	}
    49  	f := &File{&file{fd: fdi, name: name}}
    50  	runtime.SetFinalizer(f.file, (*file).close)
    51  	return f
    52  }
    53  
    54  // Auxiliary information if the File describes a directory
    55  type dirInfo struct {
    56  	buf  [syscall.STATMAX]byte // buffer for directory I/O
    57  	nbuf int                   // length of buf; return value from Read
    58  	bufp int                   // location of next record in buf.
    59  }
    60  
    61  func epipecheck(file *File, e error) {
    62  }
    63  
    64  // DevNull is the name of the operating system's ``null device.''
    65  // On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
    66  const DevNull = "/dev/null"
    67  
    68  // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
    69  func syscallMode(i FileMode) (o uint32) {
    70  	o |= uint32(i.Perm())
    71  	if i&ModeAppend != 0 {
    72  		o |= syscall.DMAPPEND
    73  	}
    74  	if i&ModeExclusive != 0 {
    75  		o |= syscall.DMEXCL
    76  	}
    77  	if i&ModeTemporary != 0 {
    78  		o |= syscall.DMTMP
    79  	}
    80  	return
    81  }
    82  
    83  // openFileNolog is the Plan 9 implementation of OpenFile.
    84  func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
    85  	var (
    86  		fd     int
    87  		e      error
    88  		create bool
    89  		excl   bool
    90  		trunc  bool
    91  		append bool
    92  	)
    93  
    94  	if flag&O_CREATE == O_CREATE {
    95  		flag = flag & ^O_CREATE
    96  		create = true
    97  	}
    98  	if flag&O_EXCL == O_EXCL {
    99  		excl = true
   100  	}
   101  	if flag&O_TRUNC == O_TRUNC {
   102  		trunc = true
   103  	}
   104  	// O_APPEND is emulated on Plan 9
   105  	if flag&O_APPEND == O_APPEND {
   106  		flag = flag &^ O_APPEND
   107  		append = true
   108  	}
   109  
   110  	if (create && trunc) || excl {
   111  		fd, e = syscall.Create(name, flag, syscallMode(perm))
   112  	} else {
   113  		fd, e = syscall.Open(name, flag)
   114  		if IsNotExist(e) && create {
   115  			fd, e = syscall.Create(name, flag, syscallMode(perm))
   116  			if e != nil {
   117  				return nil, &PathError{"create", name, e}
   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  // Close will return an error if it has already been called.
   139  func (f *File) Close() error {
   140  	if err := f.checkValid("close"); err != nil {
   141  		return err
   142  	}
   143  	return f.file.close()
   144  }
   145  
   146  func (file *file) close() error {
   147  	if file == nil || file.fd == badFd {
   148  		return ErrInvalid
   149  	}
   150  	var err error
   151  	if e := syscall.Close(file.fd); e != nil {
   152  		err = &PathError{"close", file.name, e}
   153  	}
   154  	file.fd = badFd // so it can't be closed again
   155  
   156  	// no need for a finalizer anymore
   157  	runtime.SetFinalizer(file, nil)
   158  	return err
   159  }
   160  
   161  // Stat returns the FileInfo structure describing file.
   162  // If there is an error, it will be of type *PathError.
   163  func (f *File) Stat() (FileInfo, error) {
   164  	if f == nil {
   165  		return nil, ErrInvalid
   166  	}
   167  	d, err := dirstat(f)
   168  	if err != nil {
   169  		return nil, err
   170  	}
   171  	return fileInfoFromStat(d), nil
   172  }
   173  
   174  // Truncate changes the size of the file.
   175  // It does not change the I/O offset.
   176  // If there is an error, it will be of type *PathError.
   177  func (f *File) Truncate(size int64) error {
   178  	if f == nil {
   179  		return ErrInvalid
   180  	}
   181  
   182  	var d syscall.Dir
   183  	d.Null()
   184  	d.Length = size
   185  
   186  	var buf [syscall.STATFIXLEN]byte
   187  	n, err := d.Marshal(buf[:])
   188  	if err != nil {
   189  		return &PathError{"truncate", f.name, err}
   190  	}
   191  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
   192  		return &PathError{"truncate", f.name, err}
   193  	}
   194  	return nil
   195  }
   196  
   197  const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)
   198  
   199  func (f *File) chmod(mode FileMode) error {
   200  	if f == nil {
   201  		return ErrInvalid
   202  	}
   203  	var d syscall.Dir
   204  
   205  	odir, e := dirstat(f)
   206  	if e != nil {
   207  		return &PathError{"chmod", f.name, e}
   208  	}
   209  	d.Null()
   210  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
   211  
   212  	var buf [syscall.STATFIXLEN]byte
   213  	n, err := d.Marshal(buf[:])
   214  	if err != nil {
   215  		return &PathError{"chmod", f.name, err}
   216  	}
   217  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
   218  		return &PathError{"chmod", f.name, err}
   219  	}
   220  	return nil
   221  }
   222  
   223  // Sync commits the current contents of the file to stable storage.
   224  // Typically, this means flushing the file system's in-memory copy
   225  // of recently written data to disk.
   226  func (f *File) Sync() error {
   227  	if f == nil {
   228  		return ErrInvalid
   229  	}
   230  	var d syscall.Dir
   231  	d.Null()
   232  
   233  	var buf [syscall.STATFIXLEN]byte
   234  	n, err := d.Marshal(buf[:])
   235  	if err != nil {
   236  		return &PathError{"sync", f.name, err}
   237  	}
   238  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
   239  		return &PathError{"sync", f.name, err}
   240  	}
   241  	return nil
   242  }
   243  
   244  // read reads up to len(b) bytes from the File.
   245  // It returns the number of bytes read and an error, if any.
   246  func (f *File) read(b []byte) (n int, err error) {
   247  	n, e := fixCount(syscall.Read(f.fd, b))
   248  	if n == 0 && len(b) > 0 && e == nil {
   249  		return 0, io.EOF
   250  	}
   251  	return n, e
   252  }
   253  
   254  // pread reads len(b) bytes from the File starting at byte offset off.
   255  // It returns the number of bytes read and the error, if any.
   256  // EOF is signaled by a zero count with err set to nil.
   257  func (f *File) pread(b []byte, off int64) (n int, err error) {
   258  	n, e := fixCount(syscall.Pread(f.fd, b, off))
   259  	if n == 0 && len(b) > 0 && e == nil {
   260  		return 0, io.EOF
   261  	}
   262  	return n, e
   263  }
   264  
   265  // write writes len(b) bytes to the File.
   266  // It returns the number of bytes written and an error, if any.
   267  // Since Plan 9 preserves message boundaries, never allow
   268  // a zero-byte write.
   269  func (f *File) write(b []byte) (n int, err error) {
   270  	if len(b) == 0 {
   271  		return 0, nil
   272  	}
   273  	return fixCount(syscall.Write(f.fd, b))
   274  }
   275  
   276  // pwrite writes len(b) bytes to the File starting at byte offset off.
   277  // It returns the number of bytes written and an error, if any.
   278  // Since Plan 9 preserves message boundaries, never allow
   279  // a zero-byte write.
   280  func (f *File) pwrite(b []byte, off int64) (n int, err error) {
   281  	if len(b) == 0 {
   282  		return 0, nil
   283  	}
   284  	return fixCount(syscall.Pwrite(f.fd, b, off))
   285  }
   286  
   287  // seek sets the offset for the next Read or Write on file to offset, interpreted
   288  // according to whence: 0 means relative to the origin of the file, 1 means
   289  // relative to the current offset, and 2 means relative to the end.
   290  // It returns the new offset and an error, if any.
   291  func (f *File) seek(offset int64, whence int) (ret int64, err error) {
   292  	if f.dirinfo != nil {
   293  		// Free cached dirinfo, so we allocate a new one if we
   294  		// access this file as a directory again. See #35767 and #37161.
   295  		f.dirinfo = nil
   296  	}
   297  	return syscall.Seek(f.fd, offset, whence)
   298  }
   299  
   300  // Truncate changes the size of the named file.
   301  // If the file is a symbolic link, it changes the size of the link's target.
   302  // If there is an error, it will be of type *PathError.
   303  func Truncate(name string, size int64) error {
   304  	var d syscall.Dir
   305  
   306  	d.Null()
   307  	d.Length = size
   308  
   309  	var buf [syscall.STATFIXLEN]byte
   310  	n, err := d.Marshal(buf[:])
   311  	if err != nil {
   312  		return &PathError{"truncate", name, err}
   313  	}
   314  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   315  		return &PathError{"truncate", name, err}
   316  	}
   317  	return nil
   318  }
   319  
   320  // Remove removes the named file or directory.
   321  // If there is an error, it will be of type *PathError.
   322  func Remove(name string) error {
   323  	if e := syscall.Remove(name); e != nil {
   324  		return &PathError{"remove", name, e}
   325  	}
   326  	return nil
   327  }
   328  
   329  // HasPrefix from the strings package.
   330  func hasPrefix(s, prefix string) bool {
   331  	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
   332  }
   333  
   334  // LastIndexByte from the strings package.
   335  func lastIndex(s string, sep byte) int {
   336  	for i := len(s) - 1; i >= 0; i-- {
   337  		if s[i] == sep {
   338  			return i
   339  		}
   340  	}
   341  	return -1
   342  }
   343  
   344  func rename(oldname, newname string) error {
   345  	dirname := oldname[:lastIndex(oldname, '/')+1]
   346  	if hasPrefix(newname, dirname) {
   347  		newname = newname[len(dirname):]
   348  	} else {
   349  		return &LinkError{"rename", oldname, newname, ErrInvalid}
   350  	}
   351  
   352  	// If newname still contains slashes after removing the oldname
   353  	// prefix, the rename is cross-directory and must be rejected.
   354  	if lastIndex(newname, '/') >= 0 {
   355  		return &LinkError{"rename", oldname, newname, ErrInvalid}
   356  	}
   357  
   358  	var d syscall.Dir
   359  
   360  	d.Null()
   361  	d.Name = newname
   362  
   363  	buf := make([]byte, syscall.STATFIXLEN+len(d.Name))
   364  	n, err := d.Marshal(buf[:])
   365  	if err != nil {
   366  		return &LinkError{"rename", oldname, newname, err}
   367  	}
   368  
   369  	// If newname already exists and is not a directory, rename replaces it.
   370  	f, err := Stat(dirname + newname)
   371  	if err == nil && !f.IsDir() {
   372  		Remove(dirname + newname)
   373  	}
   374  
   375  	if err = syscall.Wstat(oldname, buf[:n]); err != nil {
   376  		return &LinkError{"rename", oldname, newname, err}
   377  	}
   378  	return nil
   379  }
   380  
   381  // See docs in file.go:Chmod.
   382  func chmod(name string, mode FileMode) error {
   383  	var d syscall.Dir
   384  
   385  	odir, e := dirstat(name)
   386  	if e != nil {
   387  		return &PathError{"chmod", name, e}
   388  	}
   389  	d.Null()
   390  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
   391  
   392  	var buf [syscall.STATFIXLEN]byte
   393  	n, err := d.Marshal(buf[:])
   394  	if err != nil {
   395  		return &PathError{"chmod", name, err}
   396  	}
   397  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   398  		return &PathError{"chmod", name, err}
   399  	}
   400  	return nil
   401  }
   402  
   403  // Chtimes changes the access and modification times of the named
   404  // file, similar to the Unix utime() or utimes() functions.
   405  //
   406  // The underlying filesystem may truncate or round the values to a
   407  // less precise time unit.
   408  // If there is an error, it will be of type *PathError.
   409  func Chtimes(name string, atime time.Time, mtime time.Time) error {
   410  	var d syscall.Dir
   411  
   412  	d.Null()
   413  	d.Atime = uint32(atime.Unix())
   414  	d.Mtime = uint32(mtime.Unix())
   415  
   416  	var buf [syscall.STATFIXLEN]byte
   417  	n, err := d.Marshal(buf[:])
   418  	if err != nil {
   419  		return &PathError{"chtimes", name, err}
   420  	}
   421  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   422  		return &PathError{"chtimes", name, err}
   423  	}
   424  	return nil
   425  }
   426  
   427  // Pipe returns a connected pair of Files; reads from r return bytes
   428  // written to w. It returns the files and an error, if any.
   429  func Pipe() (r *File, w *File, err error) {
   430  	var p [2]int
   431  
   432  	if e := syscall.Pipe(p[0:]); e != nil {
   433  		return nil, nil, NewSyscallError("pipe", e)
   434  	}
   435  
   436  	return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil
   437  }
   438  
   439  // not supported on Plan 9
   440  
   441  // Link creates newname as a hard link to the oldname file.
   442  // If there is an error, it will be of type *LinkError.
   443  func Link(oldname, newname string) error {
   444  	return &LinkError{"link", oldname, newname, syscall.EPLAN9}
   445  }
   446  
   447  // Symlink creates newname as a symbolic link to oldname.
   448  // If there is an error, it will be of type *LinkError.
   449  func Symlink(oldname, newname string) error {
   450  	return &LinkError{"symlink", oldname, newname, syscall.EPLAN9}
   451  }
   452  
   453  // Readlink returns the destination of the named symbolic link.
   454  // If there is an error, it will be of type *PathError.
   455  func Readlink(name string) (string, error) {
   456  	return "", &PathError{"readlink", name, syscall.EPLAN9}
   457  }
   458  
   459  // Chown 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's target.
   461  // A uid or gid of -1 means to not change that value.
   462  // If there is an error, it will be of type *PathError.
   463  //
   464  // On Windows or Plan 9, Chown always returns the syscall.EWINDOWS or
   465  // EPLAN9 error, wrapped in *PathError.
   466  func Chown(name string, uid, gid int) error {
   467  	return &PathError{"chown", name, syscall.EPLAN9}
   468  }
   469  
   470  // Lchown changes the numeric uid and gid of the named file.
   471  // If the file is a symbolic link, it changes the uid and gid of the link itself.
   472  // If there is an error, it will be of type *PathError.
   473  func Lchown(name string, uid, gid int) error {
   474  	return &PathError{"lchown", name, syscall.EPLAN9}
   475  }
   476  
   477  // Chown changes the numeric uid and gid of the named file.
   478  // If there is an error, it will be of type *PathError.
   479  func (f *File) Chown(uid, gid int) error {
   480  	if f == nil {
   481  		return ErrInvalid
   482  	}
   483  	return &PathError{"chown", f.name, syscall.EPLAN9}
   484  }
   485  
   486  func tempDir() string {
   487  	dir := Getenv("TMPDIR")
   488  	if dir == "" {
   489  		dir = "/tmp"
   490  	}
   491  	return dir
   492  
   493  }
   494  
   495  // Chdir changes the current working directory to the file,
   496  // which must be a directory.
   497  // If there is an error, it will be of type *PathError.
   498  func (f *File) Chdir() error {
   499  	if err := f.checkValid("chdir"); err != nil {
   500  		return err
   501  	}
   502  	if e := syscall.Fchdir(f.fd); e != nil {
   503  		return &PathError{"chdir", f.name, e}
   504  	}
   505  	return nil
   506  }
   507  
   508  // setDeadline sets the read and write deadline.
   509  func (f *File) setDeadline(time.Time) error {
   510  	if err := f.checkValid("SetDeadline"); err != nil {
   511  		return err
   512  	}
   513  	return poll.ErrNoDeadline
   514  }
   515  
   516  // setReadDeadline sets the read deadline.
   517  func (f *File) setReadDeadline(time.Time) error {
   518  	if err := f.checkValid("SetReadDeadline"); err != nil {
   519  		return err
   520  	}
   521  	return poll.ErrNoDeadline
   522  }
   523  
   524  // setWriteDeadline sets the write deadline.
   525  func (f *File) setWriteDeadline(time.Time) error {
   526  	if err := f.checkValid("SetWriteDeadline"); err != nil {
   527  		return err
   528  	}
   529  	return poll.ErrNoDeadline
   530  }
   531  
   532  // checkValid checks whether f is valid for use.
   533  // If not, it returns an appropriate error, perhaps incorporating the operation name op.
   534  func (f *File) checkValid(op string) error {
   535  	if f == nil {
   536  		return ErrInvalid
   537  	}
   538  	if f.fd == badFd {
   539  		return &PathError{op, f.name, ErrClosed}
   540  	}
   541  	return nil
   542  }
   543  
   544  type rawConn struct{}
   545  
   546  func (c *rawConn) Control(f func(uintptr)) error {
   547  	return syscall.EPLAN9
   548  }
   549  
   550  func (c *rawConn) Read(f func(uintptr) bool) error {
   551  	return syscall.EPLAN9
   552  }
   553  
   554  func (c *rawConn) Write(f func(uintptr) bool) error {
   555  	return syscall.EPLAN9
   556  }
   557  
   558  func newRawConn(file *File) (*rawConn, error) {
   559  	return nil, syscall.EPLAN9
   560  }
   561  

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