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Source file src/os/file_plan9.go

Documentation: os

  // Copyright 2011 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package os
  
  import (
  	"io"
  	"runtime"
  	"syscall"
  	"time"
  )
  
  // fixLongPath is a noop on non-Windows platforms.
  func fixLongPath(path string) string {
  	return path
  }
  
  // file is the real representation of *File.
  // The extra level of indirection ensures that no clients of os
  // can overwrite this data, which could cause the finalizer
  // to close the wrong file descriptor.
  type file struct {
  	fd      int
  	name    string
  	dirinfo *dirInfo // nil unless directory being read
  }
  
  // Fd returns the integer Plan 9 file descriptor referencing the open file.
  // The file descriptor is valid only until f.Close is called or f is garbage collected.
  func (f *File) Fd() uintptr {
  	if f == nil {
  		return ^(uintptr(0))
  	}
  	return uintptr(f.fd)
  }
  
  // NewFile returns a new File with the given file descriptor and
  // name. The returned value will be nil if fd is not a valid file
  // descriptor.
  func NewFile(fd uintptr, name string) *File {
  	fdi := int(fd)
  	if fdi < 0 {
  		return nil
  	}
  	f := &File{&file{fd: fdi, name: name}}
  	runtime.SetFinalizer(f.file, (*file).close)
  	return f
  }
  
  // Auxiliary information if the File describes a directory
  type dirInfo struct {
  	buf  [syscall.STATMAX]byte // buffer for directory I/O
  	nbuf int                   // length of buf; return value from Read
  	bufp int                   // location of next record in buf.
  }
  
  func epipecheck(file *File, e error) {
  }
  
  // DevNull is the name of the operating system's ``null device.''
  // On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
  const DevNull = "/dev/null"
  
  // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
  func syscallMode(i FileMode) (o uint32) {
  	o |= uint32(i.Perm())
  	if i&ModeAppend != 0 {
  		o |= syscall.DMAPPEND
  	}
  	if i&ModeExclusive != 0 {
  		o |= syscall.DMEXCL
  	}
  	if i&ModeTemporary != 0 {
  		o |= syscall.DMTMP
  	}
  	return
  }
  
  // OpenFile is the generalized open call; most users will use Open
  // or Create instead. It opens the named file with specified flag
  // (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful,
  // methods on the returned File can be used for I/O.
  // If there is an error, it will be of type *PathError.
  func OpenFile(name string, flag int, perm FileMode) (*File, error) {
  	var (
  		fd     int
  		e      error
  		create bool
  		excl   bool
  		trunc  bool
  		append bool
  	)
  
  	if flag&O_CREATE == O_CREATE {
  		flag = flag & ^O_CREATE
  		create = true
  	}
  	if flag&O_EXCL == O_EXCL {
  		excl = true
  	}
  	if flag&O_TRUNC == O_TRUNC {
  		trunc = true
  	}
  	// O_APPEND is emulated on Plan 9
  	if flag&O_APPEND == O_APPEND {
  		flag = flag &^ O_APPEND
  		append = true
  	}
  
  	if (create && trunc) || excl {
  		fd, e = syscall.Create(name, flag, syscallMode(perm))
  	} else {
  		fd, e = syscall.Open(name, flag)
  		if e != nil && create {
  			var e1 error
  			fd, e1 = syscall.Create(name, flag, syscallMode(perm))
  			if e1 == nil {
  				e = nil
  			}
  		}
  	}
  
  	if e != nil {
  		return nil, &PathError{"open", name, e}
  	}
  
  	if append {
  		if _, e = syscall.Seek(fd, 0, io.SeekEnd); e != nil {
  			return nil, &PathError{"seek", name, e}
  		}
  	}
  
  	return NewFile(uintptr(fd), name), nil
  }
  
  // Close closes the File, rendering it unusable for I/O.
  // It returns an error, if any.
  func (f *File) Close() error {
  	if err := f.checkValid("close"); err != nil {
  		return err
  	}
  	return f.file.close()
  }
  
  func (file *file) close() error {
  	if file == nil || file.fd == badFd {
  		return ErrInvalid
  	}
  	var err error
  	if e := syscall.Close(file.fd); e != nil {
  		err = &PathError{"close", file.name, e}
  	}
  	file.fd = badFd // so it can't be closed again
  
  	// no need for a finalizer anymore
  	runtime.SetFinalizer(file, nil)
  	return err
  }
  
  // Stat returns the FileInfo structure describing file.
  // If there is an error, it will be of type *PathError.
  func (f *File) Stat() (FileInfo, error) {
  	if f == nil {
  		return nil, ErrInvalid
  	}
  	d, err := dirstat(f)
  	if err != nil {
  		return nil, err
  	}
  	return fileInfoFromStat(d), nil
  }
  
  // Truncate changes the size of the file.
  // It does not change the I/O offset.
  // If there is an error, it will be of type *PathError.
  func (f *File) Truncate(size int64) error {
  	if f == nil {
  		return ErrInvalid
  	}
  
  	var d syscall.Dir
  	d.Null()
  	d.Length = size
  
  	var buf [syscall.STATFIXLEN]byte
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return &PathError{"truncate", f.name, err}
  	}
  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
  		return &PathError{"truncate", f.name, err}
  	}
  	return nil
  }
  
  const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)
  
  func (f *File) chmod(mode FileMode) error {
  	if f == nil {
  		return ErrInvalid
  	}
  	var d syscall.Dir
  
  	odir, e := dirstat(f)
  	if e != nil {
  		return &PathError{"chmod", f.name, e}
  	}
  	d.Null()
  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
  
  	var buf [syscall.STATFIXLEN]byte
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return &PathError{"chmod", f.name, err}
  	}
  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
  		return &PathError{"chmod", f.name, err}
  	}
  	return nil
  }
  
  // Sync commits the current contents of the file to stable storage.
  // Typically, this means flushing the file system's in-memory copy
  // of recently written data to disk.
  func (f *File) Sync() error {
  	if f == nil {
  		return ErrInvalid
  	}
  	var d syscall.Dir
  	d.Null()
  
  	var buf [syscall.STATFIXLEN]byte
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return NewSyscallError("fsync", err)
  	}
  	if err = syscall.Fwstat(f.fd, buf[:n]); err != nil {
  		return NewSyscallError("fsync", err)
  	}
  	return nil
  }
  
  // read reads up to len(b) bytes from the File.
  // It returns the number of bytes read and an error, if any.
  func (f *File) read(b []byte) (n int, err error) {
  	n, e := fixCount(syscall.Read(f.fd, b))
  	if n == 0 && len(b) > 0 && e == nil {
  		return 0, io.EOF
  	}
  	return n, e
  }
  
  // pread reads len(b) bytes from the File starting at byte offset off.
  // It returns the number of bytes read and the error, if any.
  // EOF is signaled by a zero count with err set to nil.
  func (f *File) pread(b []byte, off int64) (n int, err error) {
  	n, e := fixCount(syscall.Pread(f.fd, b, off))
  	if n == 0 && len(b) > 0 && e == nil {
  		return 0, io.EOF
  	}
  	return n, e
  }
  
  // write writes len(b) bytes to the File.
  // It returns the number of bytes written and an error, if any.
  // Since Plan 9 preserves message boundaries, never allow
  // a zero-byte write.
  func (f *File) write(b []byte) (n int, err error) {
  	if len(b) == 0 {
  		return 0, nil
  	}
  	return fixCount(syscall.Write(f.fd, b))
  }
  
  // pwrite writes len(b) bytes to the File starting at byte offset off.
  // It returns the number of bytes written and an error, if any.
  // Since Plan 9 preserves message boundaries, never allow
  // a zero-byte write.
  func (f *File) pwrite(b []byte, off int64) (n int, err error) {
  	if len(b) == 0 {
  		return 0, nil
  	}
  	return fixCount(syscall.Pwrite(f.fd, b, off))
  }
  
  // seek sets the offset for the next Read or Write on file to offset, interpreted
  // according to whence: 0 means relative to the origin of the file, 1 means
  // relative to the current offset, and 2 means relative to the end.
  // It returns the new offset and an error, if any.
  func (f *File) seek(offset int64, whence int) (ret int64, err error) {
  	return syscall.Seek(f.fd, offset, whence)
  }
  
  // Truncate changes the size of the named file.
  // If the file is a symbolic link, it changes the size of the link's target.
  // If there is an error, it will be of type *PathError.
  func Truncate(name string, size int64) error {
  	var d syscall.Dir
  
  	d.Null()
  	d.Length = size
  
  	var buf [syscall.STATFIXLEN]byte
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return &PathError{"truncate", name, err}
  	}
  	if err = syscall.Wstat(name, buf[:n]); err != nil {
  		return &PathError{"truncate", name, err}
  	}
  	return nil
  }
  
  // Remove removes the named file or directory.
  // If there is an error, it will be of type *PathError.
  func Remove(name string) error {
  	if e := syscall.Remove(name); e != nil {
  		return &PathError{"remove", name, e}
  	}
  	return nil
  }
  
  // HasPrefix from the strings package.
  func hasPrefix(s, prefix string) bool {
  	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
  }
  
  // LastIndexByte from the strings package.
  func lastIndex(s string, sep byte) int {
  	for i := len(s) - 1; i >= 0; i-- {
  		if s[i] == sep {
  			return i
  		}
  	}
  	return -1
  }
  
  func rename(oldname, newname string) error {
  	dirname := oldname[:lastIndex(oldname, '/')+1]
  	if hasPrefix(newname, dirname) {
  		newname = newname[len(dirname):]
  	} else {
  		return &LinkError{"rename", oldname, newname, ErrInvalid}
  	}
  
  	// If newname still contains slashes after removing the oldname
  	// prefix, the rename is cross-directory and must be rejected.
  	if lastIndex(newname, '/') >= 0 {
  		return &LinkError{"rename", oldname, newname, ErrInvalid}
  	}
  
  	var d syscall.Dir
  
  	d.Null()
  	d.Name = newname
  
  	buf := make([]byte, syscall.STATFIXLEN+len(d.Name))
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return &LinkError{"rename", oldname, newname, err}
  	}
  
  	// If newname already exists and is not a directory, rename replaces it.
  	f, err := Stat(dirname + newname)
  	if err == nil && !f.IsDir() {
  		Remove(dirname + newname)
  	}
  
  	if err = syscall.Wstat(oldname, buf[:n]); err != nil {
  		return &LinkError{"rename", oldname, newname, err}
  	}
  	return nil
  }
  
  // See docs in file.go:Chmod.
  func chmod(name string, mode FileMode) error {
  	var d syscall.Dir
  
  	odir, e := dirstat(name)
  	if e != nil {
  		return &PathError{"chmod", name, e}
  	}
  	d.Null()
  	d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask
  
  	var buf [syscall.STATFIXLEN]byte
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return &PathError{"chmod", name, err}
  	}
  	if err = syscall.Wstat(name, buf[:n]); err != nil {
  		return &PathError{"chmod", name, err}
  	}
  	return nil
  }
  
  // Chtimes changes the access and modification times of the named
  // file, similar to the Unix utime() or utimes() functions.
  //
  // The underlying filesystem may truncate or round the values to a
  // less precise time unit.
  // If there is an error, it will be of type *PathError.
  func Chtimes(name string, atime time.Time, mtime time.Time) error {
  	var d syscall.Dir
  
  	d.Null()
  	d.Atime = uint32(atime.Unix())
  	d.Mtime = uint32(mtime.Unix())
  
  	var buf [syscall.STATFIXLEN]byte
  	n, err := d.Marshal(buf[:])
  	if err != nil {
  		return &PathError{"chtimes", name, err}
  	}
  	if err = syscall.Wstat(name, buf[:n]); err != nil {
  		return &PathError{"chtimes", name, err}
  	}
  	return nil
  }
  
  // Pipe returns a connected pair of Files; reads from r return bytes
  // written to w. It returns the files and an error, if any.
  func Pipe() (r *File, w *File, err error) {
  	var p [2]int
  
  	if e := syscall.Pipe(p[0:]); e != nil {
  		return nil, nil, NewSyscallError("pipe", e)
  	}
  
  	return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil
  }
  
  // not supported on Plan 9
  
  // Link creates newname as a hard link to the oldname file.
  // If there is an error, it will be of type *LinkError.
  func Link(oldname, newname string) error {
  	return &LinkError{"link", oldname, newname, syscall.EPLAN9}
  }
  
  // Symlink creates newname as a symbolic link to oldname.
  // If there is an error, it will be of type *LinkError.
  func Symlink(oldname, newname string) error {
  	return &LinkError{"symlink", oldname, newname, syscall.EPLAN9}
  }
  
  // Readlink returns the destination of the named symbolic link.
  // If there is an error, it will be of type *PathError.
  func Readlink(name string) (string, error) {
  	return "", &PathError{"readlink", name, syscall.EPLAN9}
  }
  
  // Chown changes the numeric uid and gid of the named file.
  // If the file is a symbolic link, it changes the uid and gid of the link's target.
  // If there is an error, it will be of type *PathError.
  func Chown(name string, uid, gid int) error {
  	return &PathError{"chown", name, syscall.EPLAN9}
  }
  
  // Lchown changes the numeric uid and gid of the named file.
  // If the file is a symbolic link, it changes the uid and gid of the link itself.
  // If there is an error, it will be of type *PathError.
  func Lchown(name string, uid, gid int) error {
  	return &PathError{"lchown", name, syscall.EPLAN9}
  }
  
  // Chown changes the numeric uid and gid of the named file.
  // If there is an error, it will be of type *PathError.
  func (f *File) Chown(uid, gid int) error {
  	if f == nil {
  		return ErrInvalid
  	}
  	return &PathError{"chown", f.name, syscall.EPLAN9}
  }
  
  func tempDir() string {
  	return "/tmp"
  }
  
  // Chdir changes the current working directory to the file,
  // which must be a directory.
  // If there is an error, it will be of type *PathError.
  func (f *File) Chdir() error {
  	if err := f.checkValid("chdir"); err != nil {
  		return err
  	}
  	if e := syscall.Fchdir(f.fd); e != nil {
  		return &PathError{"chdir", f.name, e}
  	}
  	return nil
  }
  
  // checkValid checks whether f is valid for use.
  // If not, it returns an appropriate error, perhaps incorporating the operation name op.
  func (f *File) checkValid(op string) error {
  	if f == nil {
  		return ErrInvalid
  	}
  	if f.fd == badFd {
  		return &PathError{op, f.name, ErrClosed}
  	}
  	return nil
  }
  

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