file_plan9.go

     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/bytealg"
     9  	"internal/poll"
    10  	"internal/stringslite"
    11  	"io"
    12  	"runtime"
    13  	"sync"
    14  	"sync/atomic"
    15  	"syscall"
    16  	"time"
    17  )
    18  
    19  // fixLongPath is a noop on non-Windows platforms.
    20  func fixLongPath(path string) string {
    21  	return path
    22  }
    23  
    24  // file is the real representation of *File.
    25  // The extra level of indirection ensures that no clients of os
    26  // can overwrite this data, which could cause the finalizer
    27  // to close the wrong file descriptor.
    28  type file struct {
    29  	fdmu       poll.FDMutex
    30  	sysfd      int
    31  	name       string
    32  	dirinfo    atomic.Pointer[dirInfo] // nil unless directory being read
    33  	appendMode bool                    // whether file is opened for appending
    34  }
    35  
    36  // fd is the Plan 9 implementation of Fd.
    37  func (f *File) fd() uintptr {
    38  	if f == nil {
    39  		return ^(uintptr(0))
    40  	}
    41  	return uintptr(f.sysfd)
    42  }
    43  
    44  // newFileFromNewFile is called by [NewFile].
    45  func newFileFromNewFile(fd uintptr, name string) *File {
    46  	fdi := int(fd)
    47  	if fdi < 0 {
    48  		return nil
    49  	}
    50  	f := &File{&file{sysfd: fdi, name: name}}
    51  	runtime.SetFinalizer(f.file, (*file).close)
    52  	return f
    53  }
    54  
    55  // Auxiliary information if the File describes a directory
    56  type dirInfo struct {
    57  	mu   sync.Mutex
    58  	buf  [syscall.STATMAX]byte // buffer for directory I/O
    59  	nbuf int                   // length of buf; return value from Read
    60  	bufp int                   // location of next record in buf.
    61  }
    62  
    63  func epipecheck(file *File, e error) {
    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  // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
    71  func syscallMode(i FileMode) (o uint32) {
    72  	o |= uint32(i.Perm())
    73  	if i&ModeAppend != 0 {
    74  		o |= syscall.DMAPPEND
    75  	}
    76  	if i&ModeExclusive != 0 {
    77  		o |= syscall.DMEXCL
    78  	}
    79  	if i&ModeTemporary != 0 {
    80  		o |= syscall.DMTMP
    81  	}
    82  	return
    83  }
    84  
    85  // openFileNolog is the Plan 9 implementation of OpenFile.
    86  func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
    87  	var (
    88  		fd     int
    89  		e      error
    90  		create bool
    91  		excl   bool
    92  		trunc  bool
    93  		append bool
    94  	)
    95  
    96  	if flag&O_CREATE == O_CREATE {
    97  		flag = flag & ^O_CREATE
    98  		create = true
    99  	}
   100  	if flag&O_EXCL == O_EXCL {
   101  		excl = true
   102  	}
   103  	if flag&O_TRUNC == O_TRUNC {
   104  		trunc = true
   105  	}
   106  	// O_APPEND is emulated on Plan 9
   107  	if flag&O_APPEND == O_APPEND {
   108  		flag = flag &^ O_APPEND
   109  		append = true
   110  	}
   111  
   112  	if (create && trunc) || excl {
   113  		fd, e = syscall.Create(name, flag, syscallMode(perm))
   114  	} else {
   115  		fd, e = syscall.Open(name, flag)
   116  		if IsNotExist(e) && create {
   117  			fd, e = syscall.Create(name, flag, syscallMode(perm))
   118  			if e != nil {
   119  				return nil, &PathError{Op: "create", Path: name, Err: e}
   120  			}
   121  		}
   122  	}
   123  
   124  	if e != nil {
   125  		return nil, &PathError{Op: "open", Path: name, Err: e}
   126  	}
   127  
   128  	if append {
   129  		if _, e = syscall.Seek(fd, 0, io.SeekEnd); e != nil {
   130  			return nil, &PathError{Op: "seek", Path: name, Err: e}
   131  		}
   132  	}
   133  
   134  	return NewFile(uintptr(fd), name), nil
   135  }
   136  
   137  func openDirNolog(name string) (*File, error) {
   138  	f, e := openFileNolog(name, O_RDONLY, 0)
   139  	if e != nil {
   140  		return nil, e
   141  	}
   142  	d, e := f.Stat()
   143  	if e != nil {
   144  		f.Close()
   145  		return nil, e
   146  	}
   147  	if !d.IsDir() {
   148  		f.Close()
   149  		return nil, &PathError{Op: "open", Path: name, Err: syscall.ENOTDIR}
   150  	}
   151  	return f, nil
   152  }
   153  
   154  // Close closes the File, rendering it unusable for I/O.
   155  // On files that support SetDeadline, any pending I/O operations will
   156  // be canceled and return immediately with an ErrClosed error.
   157  // Close will return an error if it has already been called.
   158  func (f *File) Close() error {
   159  	if f == nil {
   160  		return ErrInvalid
   161  	}
   162  	return f.file.close()
   163  }
   164  
   165  func (file *file) close() error {
   166  	if !file.fdmu.IncrefAndClose() {
   167  		return &PathError{Op: "close", Path: file.name, Err: ErrClosed}
   168  	}
   169  
   170  	// At this point we should cancel any pending I/O.
   171  	// How do we do that on Plan 9?
   172  
   173  	err := file.decref()
   174  
   175  	// no need for a finalizer anymore
   176  	runtime.SetFinalizer(file, nil)
   177  	return err
   178  }
   179  
   180  // destroy actually closes the descriptor. This is called when
   181  // there are no remaining references, by the decref, readUnlock,
   182  // and writeUnlock methods.
   183  func (file *file) destroy() error {
   184  	var err error
   185  	if e := syscall.Close(file.sysfd); e != nil {
   186  		err = &PathError{Op: "close", Path: file.name, Err: e}
   187  	}
   188  	return err
   189  }
   190  
   191  // Stat returns the FileInfo structure describing file.
   192  // If there is an error, it will be of type [*PathError].
   193  func (f *File) Stat() (FileInfo, error) {
   194  	if f == nil {
   195  		return nil, ErrInvalid
   196  	}
   197  	d, err := dirstat(f)
   198  	if err != nil {
   199  		return nil, err
   200  	}
   201  	return fileInfoFromStat(d), nil
   202  }
   203  
   204  // Truncate changes the size of the file.
   205  // It does not change the I/O offset.
   206  // If there is an error, it will be of type [*PathError].
   207  func (f *File) Truncate(size int64) error {
   208  	if f == nil {
   209  		return ErrInvalid
   210  	}
   211  
   212  	var d syscall.Dir
   213  	d.Null()
   214  	d.Length = size
   215  
   216  	var buf [syscall.STATFIXLEN]byte
   217  	n, err := d.Marshal(buf[:])
   218  	if err != nil {
   219  		return &PathError{Op: "truncate", Path: f.name, Err: err}
   220  	}
   221  
   222  	if err := f.incref("truncate"); err != nil {
   223  		return err
   224  	}
   225  	defer f.decref()
   226  
   227  	if err = syscall.Fwstat(f.sysfd, buf[:n]); err != nil {
   228  		return &PathError{Op: "truncate", Path: f.name, Err: err}
   229  	}
   230  	return nil
   231  }
   232  
   233  const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)
   234  
   235  func (f *File) chmod(mode FileMode) error {
   236  	if f == nil {
   237  		return ErrInvalid
   238  	}
   239  	var d syscall.Dir
   240  
   241  	odir, e := dirstat(f)
   242  	if e != nil {
   243  		return &PathError{Op: "chmod", Path: f.name, Err: e}
   244  	}
   245  	d.Null()
   246  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
   247  
   248  	var buf [syscall.STATFIXLEN]byte
   249  	n, err := d.Marshal(buf[:])
   250  	if err != nil {
   251  		return &PathError{Op: "chmod", Path: f.name, Err: err}
   252  	}
   253  
   254  	if err := f.incref("chmod"); err != nil {
   255  		return err
   256  	}
   257  	defer f.decref()
   258  
   259  	if err = syscall.Fwstat(f.sysfd, buf[:n]); err != nil {
   260  		return &PathError{Op: "chmod", Path: f.name, Err: err}
   261  	}
   262  	return nil
   263  }
   264  
   265  // Sync commits the current contents of the file to stable storage.
   266  // Typically, this means flushing the file system's in-memory copy
   267  // of recently written data to disk.
   268  func (f *File) Sync() error {
   269  	if f == nil {
   270  		return ErrInvalid
   271  	}
   272  	var d syscall.Dir
   273  	d.Null()
   274  
   275  	var buf [syscall.STATFIXLEN]byte
   276  	n, err := d.Marshal(buf[:])
   277  	if err != nil {
   278  		return &PathError{Op: "sync", Path: f.name, Err: err}
   279  	}
   280  
   281  	if err := f.incref("sync"); err != nil {
   282  		return err
   283  	}
   284  	defer f.decref()
   285  
   286  	if err = syscall.Fwstat(f.sysfd, buf[:n]); err != nil {
   287  		return &PathError{Op: "sync", Path: f.name, Err: err}
   288  	}
   289  	return nil
   290  }
   291  
   292  // read reads up to len(b) bytes from the File.
   293  // It returns the number of bytes read and an error, if any.
   294  func (f *File) read(b []byte) (n int, err error) {
   295  	if err := f.readLock(); err != nil {
   296  		return 0, err
   297  	}
   298  	defer f.readUnlock()
   299  	n, e := fixCount(syscall.Read(f.sysfd, b))
   300  	if n == 0 && len(b) > 0 && e == nil {
   301  		return 0, io.EOF
   302  	}
   303  	return n, e
   304  }
   305  
   306  // pread reads len(b) bytes from the File starting at byte offset off.
   307  // It returns the number of bytes read and the error, if any.
   308  // EOF is signaled by a zero count with err set to nil.
   309  func (f *File) pread(b []byte, off int64) (n int, err error) {
   310  	if err := f.readLock(); err != nil {
   311  		return 0, err
   312  	}
   313  	defer f.readUnlock()
   314  	n, e := fixCount(syscall.Pread(f.sysfd, b, off))
   315  	if n == 0 && len(b) > 0 && e == nil {
   316  		return 0, io.EOF
   317  	}
   318  	return n, e
   319  }
   320  
   321  // write writes len(b) bytes to the File.
   322  // It returns the number of bytes written and an error, if any.
   323  // Since Plan 9 preserves message boundaries, never allow
   324  // a zero-byte write.
   325  func (f *File) write(b []byte) (n int, err error) {
   326  	if err := f.writeLock(); err != nil {
   327  		return 0, err
   328  	}
   329  	defer f.writeUnlock()
   330  	if len(b) == 0 {
   331  		return 0, nil
   332  	}
   333  	return fixCount(syscall.Write(f.sysfd, b))
   334  }
   335  
   336  // pwrite writes len(b) bytes to the File starting at byte offset off.
   337  // It returns the number of bytes written and an error, if any.
   338  // Since Plan 9 preserves message boundaries, never allow
   339  // a zero-byte write.
   340  func (f *File) pwrite(b []byte, off int64) (n int, err error) {
   341  	if err := f.writeLock(); err != nil {
   342  		return 0, err
   343  	}
   344  	defer f.writeUnlock()
   345  	if len(b) == 0 {
   346  		return 0, nil
   347  	}
   348  	return fixCount(syscall.Pwrite(f.sysfd, b, off))
   349  }
   350  
   351  // seek sets the offset for the next Read or Write on file to offset, interpreted
   352  // according to whence: 0 means relative to the origin of the file, 1 means
   353  // relative to the current offset, and 2 means relative to the end.
   354  // It returns the new offset and an error, if any.
   355  func (f *File) seek(offset int64, whence int) (ret int64, err error) {
   356  	if err := f.incref(""); err != nil {
   357  		return 0, err
   358  	}
   359  	defer f.decref()
   360  	// Free cached dirinfo, so we allocate a new one if we
   361  	// access this file as a directory again. See #35767 and #37161.
   362  	f.dirinfo.Store(nil)
   363  	return syscall.Seek(f.sysfd, offset, whence)
   364  }
   365  
   366  // Truncate changes the size of the named file.
   367  // If the file is a symbolic link, it changes the size of the link's target.
   368  // If there is an error, it will be of type [*PathError].
   369  func Truncate(name string, size int64) error {
   370  	var d syscall.Dir
   371  
   372  	d.Null()
   373  	d.Length = size
   374  
   375  	var buf [syscall.STATFIXLEN]byte
   376  	n, err := d.Marshal(buf[:])
   377  	if err != nil {
   378  		return &PathError{Op: "truncate", Path: name, Err: err}
   379  	}
   380  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   381  		return &PathError{Op: "truncate", Path: name, Err: err}
   382  	}
   383  	return nil
   384  }
   385  
   386  // Remove removes the named file or directory.
   387  // If there is an error, it will be of type [*PathError].
   388  func Remove(name string) error {
   389  	if e := syscall.Remove(name); e != nil {
   390  		return &PathError{Op: "remove", Path: name, Err: e}
   391  	}
   392  	return nil
   393  }
   394  
   395  func rename(oldname, newname string) error {
   396  	dirname := oldname[:bytealg.LastIndexByteString(oldname, '/')+1]
   397  	if stringslite.HasPrefix(newname, dirname) {
   398  		newname = newname[len(dirname):]
   399  	} else {
   400  		return &LinkError{"rename", oldname, newname, ErrInvalid}
   401  	}
   402  
   403  	// If newname still contains slashes after removing the oldname
   404  	// prefix, the rename is cross-directory and must be rejected.
   405  	if bytealg.LastIndexByteString(newname, '/') >= 0 {
   406  		return &LinkError{"rename", oldname, newname, ErrInvalid}
   407  	}
   408  
   409  	var d syscall.Dir
   410  
   411  	d.Null()
   412  	d.Name = newname
   413  
   414  	buf := make([]byte, syscall.STATFIXLEN+len(d.Name))
   415  	n, err := d.Marshal(buf[:])
   416  	if err != nil {
   417  		return &LinkError{"rename", oldname, newname, err}
   418  	}
   419  
   420  	// If newname already exists and is not a directory, rename replaces it.
   421  	f, err := Stat(dirname + newname)
   422  	if err == nil && !f.IsDir() {
   423  		Remove(dirname + newname)
   424  	}
   425  
   426  	if err = syscall.Wstat(oldname, buf[:n]); err != nil {
   427  		return &LinkError{"rename", oldname, newname, err}
   428  	}
   429  	return nil
   430  }
   431  
   432  // See docs in file.go:Chmod.
   433  func chmod(name string, mode FileMode) error {
   434  	var d syscall.Dir
   435  
   436  	odir, e := dirstat(name)
   437  	if e != nil {
   438  		return &PathError{Op: "chmod", Path: name, Err: e}
   439  	}
   440  	d.Null()
   441  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
   442  
   443  	var buf [syscall.STATFIXLEN]byte
   444  	n, err := d.Marshal(buf[:])
   445  	if err != nil {
   446  		return &PathError{Op: "chmod", Path: name, Err: err}
   447  	}
   448  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   449  		return &PathError{Op: "chmod", Path: name, Err: err}
   450  	}
   451  	return nil
   452  }
   453  
   454  // Chtimes changes the access and modification times of the named
   455  // file, similar to the Unix utime() or utimes() functions.
   456  // A zero time.Time value will leave the corresponding file time unchanged.
   457  //
   458  // The underlying filesystem may truncate or round the values to a
   459  // less precise time unit.
   460  // If there is an error, it will be of type [*PathError].
   461  func Chtimes(name string, atime time.Time, mtime time.Time) error {
   462  	var d syscall.Dir
   463  
   464  	d.Null()
   465  	d.Atime = uint32(atime.Unix())
   466  	d.Mtime = uint32(mtime.Unix())
   467  	if atime.IsZero() {
   468  		d.Atime = 0xFFFFFFFF
   469  	}
   470  	if mtime.IsZero() {
   471  		d.Mtime = 0xFFFFFFFF
   472  	}
   473  
   474  	var buf [syscall.STATFIXLEN]byte
   475  	n, err := d.Marshal(buf[:])
   476  	if err != nil {
   477  		return &PathError{Op: "chtimes", Path: name, Err: err}
   478  	}
   479  	if err = syscall.Wstat(name, buf[:n]); err != nil {
   480  		return &PathError{Op: "chtimes", Path: name, Err: err}
   481  	}
   482  	return nil
   483  }
   484  
   485  // Pipe returns a connected pair of Files; reads from r return bytes
   486  // written to w. It returns the files and an error, if any.
   487  func Pipe() (r *File, w *File, err error) {
   488  	var p [2]int
   489  
   490  	if e := syscall.Pipe(p[0:]); e != nil {
   491  		return nil, nil, NewSyscallError("pipe", e)
   492  	}
   493  
   494  	return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil
   495  }
   496  
   497  // not supported on Plan 9
   498  
   499  // Link creates newname as a hard link to the oldname file.
   500  // If there is an error, it will be of type *LinkError.
   501  func Link(oldname, newname string) error {
   502  	return &LinkError{"link", oldname, newname, syscall.EPLAN9}
   503  }
   504  
   505  // Symlink creates newname as a symbolic link to oldname.
   506  // On Windows, a symlink to a non-existent oldname creates a file symlink;
   507  // if oldname is later created as a directory the symlink will not work.
   508  // If there is an error, it will be of type *LinkError.
   509  func Symlink(oldname, newname string) error {
   510  	return &LinkError{"symlink", oldname, newname, syscall.EPLAN9}
   511  }
   512  
   513  func readlink(name string) (string, error) {
   514  	return "", &PathError{Op: "readlink", Path: name, Err: syscall.EPLAN9}
   515  }
   516  
   517  // Chown changes the numeric uid and gid of the named file.
   518  // If the file is a symbolic link, it changes the uid and gid of the link's target.
   519  // A uid or gid of -1 means to not change that value.
   520  // If there is an error, it will be of type [*PathError].
   521  //
   522  // On Windows or Plan 9, Chown always returns the [syscall.EWINDOWS] or
   523  // [syscall.EPLAN9] error, wrapped in [*PathError].
   524  func Chown(name string, uid, gid int) error {
   525  	return &PathError{Op: "chown", Path: name, Err: syscall.EPLAN9}
   526  }
   527  
   528  // Lchown changes the numeric uid and gid of the named file.
   529  // If the file is a symbolic link, it changes the uid and gid of the link itself.
   530  // If there is an error, it will be of type [*PathError].
   531  func Lchown(name string, uid, gid int) error {
   532  	return &PathError{Op: "lchown", Path: name, Err: syscall.EPLAN9}
   533  }
   534  
   535  // Chown changes the numeric uid and gid of the named file.
   536  // If there is an error, it will be of type [*PathError].
   537  func (f *File) Chown(uid, gid int) error {
   538  	if f == nil {
   539  		return ErrInvalid
   540  	}
   541  	return &PathError{Op: "chown", Path: f.name, Err: syscall.EPLAN9}
   542  }
   543  
   544  func tempDir() string {
   545  	dir := Getenv("TMPDIR")
   546  	if dir == "" {
   547  		dir = "/tmp"
   548  	}
   549  	return dir
   550  }
   551  
   552  // Chdir changes the current working directory to the file,
   553  // which must be a directory.
   554  // If there is an error, it will be of type [*PathError].
   555  func (f *File) Chdir() error {
   556  	if err := f.incref("chdir"); err != nil {
   557  		return err
   558  	}
   559  	defer f.decref()
   560  	if e := syscall.Fchdir(f.sysfd); e != nil {
   561  		return &PathError{Op: "chdir", Path: f.name, Err: e}
   562  	}
   563  	return nil
   564  }
   565  
   566  // setDeadline sets the read and write deadline.
   567  func (f *File) setDeadline(time.Time) error {
   568  	if err := f.checkValid("SetDeadline"); err != nil {
   569  		return err
   570  	}
   571  	return poll.ErrNoDeadline
   572  }
   573  
   574  // setReadDeadline sets the read deadline.
   575  func (f *File) setReadDeadline(time.Time) error {
   576  	if err := f.checkValid("SetReadDeadline"); err != nil {
   577  		return err
   578  	}
   579  	return poll.ErrNoDeadline
   580  }
   581  
   582  // setWriteDeadline sets the write deadline.
   583  func (f *File) setWriteDeadline(time.Time) error {
   584  	if err := f.checkValid("SetWriteDeadline"); err != nil {
   585  		return err
   586  	}
   587  	return poll.ErrNoDeadline
   588  }
   589  
   590  // checkValid checks whether f is valid for use, but does not prepare
   591  // to actually use it. If f is not ready checkValid returns an appropriate
   592  // error, perhaps incorporating the operation name op.
   593  func (f *File) checkValid(op string) error {
   594  	if f == nil {
   595  		return ErrInvalid
   596  	}
   597  	if err := f.incref(op); err != nil {
   598  		return err
   599  	}
   600  	return f.decref()
   601  }
   602  
   603  type rawConn struct{}
   604  
   605  func (c *rawConn) Control(f func(uintptr)) error {
   606  	return syscall.EPLAN9
   607  }
   608  
   609  func (c *rawConn) Read(f func(uintptr) bool) error {
   610  	return syscall.EPLAN9
   611  }
   612  
   613  func (c *rawConn) Write(f func(uintptr) bool) error {
   614  	return syscall.EPLAN9
   615  }
   616  
   617  func newRawConn(file *File) (*rawConn, error) {
   618  	return nil, syscall.EPLAN9
   619  }
   620  
   621  func ignoringEINTR(fn func() error) error {
   622  	return fn()
   623  }
   624  
   625  func ignoringEINTR2[T any](fn func() (T, error)) (T, error) {
   626  	return fn()
   627  }
   628
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