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// Copyright 2009 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.
// The os package provides a platform-independent interface to operating
// system functionality. The design is Unix-like.
package os
import (
"syscall";
)
// Auxiliary information if the File describes a directory
type dirInfo struct {
buf []byte; // buffer for directory I/O
nbuf int; // length of buf; return value from Getdirentries
bufp int; // location of next record in buf.
}
// File represents an open file descriptor.
type File struct {
fd int;
name string;
dirinfo *dirInfo; // nil unless directory being read
nepipe int; // number of consecutive EPIPE in Write
}
// Fd returns the integer Unix file descriptor referencing the open file.
func (file *File) Fd() int {
return file.fd
}
// Name returns the name of the file as presented to Open.
func (file *File) Name() string {
return file.name
}
// NewFile returns a new File with the given file descriptor and name.
func NewFile(fd int, name string) *File {
if fd < 0 {
return nil
}
return &File{fd, name, nil, 0}
}
// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
// standard output, and standard error file descriptors.
var (
Stdin = NewFile(0, "/dev/stdin");
Stdout = NewFile(1, "/dev/stdout");
Stderr = NewFile(2, "/dev/stderr");
)
// Flags to Open wrapping those of the underlying system. Not all flags
// may be implemented on a given system.
const (
O_RDONLY = syscall.O_RDONLY; // open the file read-only.
O_WRONLY = syscall.O_WRONLY; // open the file write-only.
O_RDWR = syscall.O_RDWR; // open the file read-write.
O_APPEND = syscall.O_APPEND; // open the file append-only.
O_ASYNC = syscall.O_ASYNC; // generate a signal when I/O is available.
O_CREAT = syscall.O_CREAT; // create a new file if none exists.
O_NOCTTY = syscall.O_NOCTTY; // do not make file the controlling tty.
O_NONBLOCK = syscall.O_NONBLOCK; // open in non-blocking mode.
O_NDELAY = O_NONBLOCK; // synonym for O_NONBLOCK
O_SYNC = syscall.O_SYNC; // open for synchronous I/O.
O_TRUNC = syscall.O_TRUNC; // if possible, truncate file when opened.
)
// Open 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.
// It returns the File and an Error, if any.
func Open(name string, flag int, perm int) (file *File, err Error) {
r, e := syscall.Open(name, flag | syscall.O_CLOEXEC, perm);
if e != 0 {
return nil, &PathError{"open", name, Errno(e)};
}
// There's a race here with fork/exec, which we are
// content to live with. See ../syscall/exec.go
if syscall.O_CLOEXEC == 0 { // O_CLOEXEC not supported
syscall.CloseOnExec(r);
}
return NewFile(r, name), nil;
}
// Close closes the File, rendering it unusable for I/O.
// It returns an Error, if any.
func (file *File) Close() Error {
if file == nil {
return EINVAL
}
var err Error;
if e := syscall.Close(file.fd); e != 0 {
err = &PathError{"close", file.name, Errno(e)};
}
file.fd = -1; // so it can't be closed again
return err;
}
type eofError int
func (eofError) String() string {
return "EOF"
}
// EOF is the Error returned by Read when no more input is available.
// Functions should return EOF only to signal a graceful end of input.
// If the EOF occurs unexpectedly in a structured data stream,
// the appropriate error is either io.ErrUnexpectedEOF or some other error
// giving more detail.
var EOF Error = eofError(0)
// Read reads up to len(b) bytes from the File.
// It returns the number of bytes read and an Error, if any.
// EOF is signaled by a zero count with err set to EOF.
// TODO(r): Add Pread, Pwrite (maybe ReadAt, WriteAt).
func (file *File) Read(b []byte) (n int, err Error) {
if file == nil {
return 0, EINVAL
}
n, e := syscall.Read(file.fd, b);
if n < 0 {
n = 0;
}
if n == 0 && e == 0 {
return 0, EOF
}
if e != 0 {
err = &PathError{"read", file.name, Errno(e)};
}
return n, err
}
// ReadAt 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 EOF.
// ReadAt always returns a non-nil Error when n != len(b).
func (file *File) ReadAt(b []byte, off int64) (n int, err Error) {
if file == nil {
return 0, EINVAL;
}
for len(b) > 0 {
m, e := syscall.Pread(file.fd, b, off);
n += m;
if e != 0 {
err = &PathError{"read", file.name, Errno(e)};
break;
}
b = b[m:len(b)];
off += int64(m);
}
return;
}
// Write writes len(b) bytes to the File.
// It returns the number of bytes written and an Error, if any.
// Write returns a non-nil Error when n != len(b).
func (file *File) Write(b []byte) (n int, err Error) {
if file == nil {
return 0, EINVAL
}
n, e := syscall.Write(file.fd, b);
if n < 0 {
n = 0
}
if e == syscall.EPIPE {
file.nepipe++;
if file.nepipe >= 10 {
Exit(syscall.EPIPE);
}
} else {
file.nepipe = 0;
}
if e != 0 {
err = &PathError{"write", file.name, Errno(e)};
}
return n, err
}
// WriteAt writes len(b) bytes to the File starting at byte offset off.
// It returns the number of bytes written and an Error, if any.
// WriteAt returns a non-nil Error when n != len(b).
func (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
if file == nil {
return 0, EINVAL;
}
for len(b) > 0 {
m, e := syscall.Pwrite(file.fd, b, off);
n += m;
if e != 0 {
err = &PathError{"write", file.name, Errno(e)};
break;
}
b = b[m:len(b)];
off += int64(m);
}
return;
}
// 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 (file *File) Seek(offset int64, whence int) (ret int64, err Error) {
r, e := syscall.Seek(file.fd, offset, whence);
if e == 0 && file.dirinfo != nil && r != 0 {
e = syscall.EISDIR;
}
if e != 0 {
return 0, &PathError{"seek", file.name, Errno(e)};
}
return r, nil
}
// WriteString is like Write, but writes the contents of string s rather than
// an array of bytes.
func (file *File) WriteString(s string) (ret int, err Error) {
if file == nil {
return 0, EINVAL
}
b := syscall.StringByteSlice(s);
b = b[0:len(b)-1];
return file.Write(b);
}
// 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;
// See ../syscall/exec.go for description of lock.
syscall.ForkLock.RLock();
e := syscall.Pipe(&p);
if e != 0 {
syscall.ForkLock.RUnlock();
return nil, nil, NewSyscallError("pipe", e);
}
syscall.CloseOnExec(p[0]);
syscall.CloseOnExec(p[1]);
syscall.ForkLock.RUnlock();
return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
}
// Mkdir creates a new directory with the specified name and permission bits.
// It returns an error, if any.
func Mkdir(name string, perm int) Error {
e := syscall.Mkdir(name, perm);
if e != 0 {
return &PathError{"mkdir", name, Errno(e)};
}
return nil;
}
// Stat returns a Dir structure describing the named file and an error, if any.
// If name names a valid symbolic link, the returned Dir describes
// the file pointed at by the link and has dir.FollowedSymlink set to true.
// If name names an invalid symbolic link, the returned Dir describes
// the link itself and has dir.FollowedSymlink set to false.
func Stat(name string) (dir *Dir, err Error) {
var lstat, stat syscall.Stat_t;
e := syscall.Lstat(name, &lstat);
if e != 0 {
return nil, &PathError{"stat", name, Errno(e)};
}
statp := &lstat;
if lstat.Mode & syscall.S_IFMT == syscall.S_IFLNK {
e := syscall.Stat(name, &stat);
if e == 0 {
statp = &stat;
}
}
return dirFromStat(name, new(Dir), &lstat, statp), nil
}
// Stat returns the Dir structure describing file.
// It returns the Dir and an error, if any.
func (file *File) Stat() (dir *Dir, err Error) {
var stat syscall.Stat_t;
e := syscall.Fstat(file.fd, &stat);
if e != 0 {
return nil, &PathError{"stat", file.name, Errno(e)};
}
return dirFromStat(file.name, new(Dir), &stat, &stat), nil
}
// Lstat returns the Dir structure describing the named file and an error, if any.
// If the file is a symbolic link, the returned Dir describes the
// symbolic link. Lstat makes no attempt to follow the link.
func Lstat(name string) (dir *Dir, err Error) {
var stat syscall.Stat_t;
e := syscall.Lstat(name, &stat);
if e != 0 {
return nil, &PathError{"lstat", name, Errno(e)};
}
return dirFromStat(name, new(Dir), &stat, &stat), nil
}
// Readdir reads the contents of the directory associated with file and
// returns an array of up to count Dir structures, as would be returned
// by Stat, in directory order. Subsequent calls on the same file will yield further Dirs.
// A negative count means to read until EOF.
// Readdir returns the array and an Error, if any.
func (file *File) Readdir(count int) (dirs []Dir, err Error) {
dirname := file.name;
if dirname == "" {
dirname = ".";
}
dirname += "/";
names, err1 := file.Readdirnames(count);
if err1 != nil {
return nil, err1
}
dirs = make([]Dir, len(names));
for i, filename := range names {
dirp, err := Stat(dirname + filename);
if dirp == nil || err != nil {
dirs[i].Name = filename // rest is already zeroed out
} else {
dirs[i] = *dirp
}
}
return
}
// Chdir changes the current working directory to the named directory.
func Chdir(dir string) Error {
if e := syscall.Chdir(dir); e != 0 {
return &PathError{"chdir", dir, Errno(e)};
}
return nil;
}
// Chdir changes the current working directory to the file,
// which must be a directory.
func (f *File) Chdir() Error {
if e := syscall.Fchdir(f.fd); e != 0 {
return &PathError{"chdir", f.name, Errno(e)};
}
return nil;
}
// Remove removes the named file or directory.
func Remove(name string) Error {
// System call interface forces us to know
// whether name is a file or directory.
// Try both: it is cheaper on average than
// doing a Stat plus the right one.
e := syscall.Unlink(name);
if e == 0 {
return nil;
}
e1 := syscall.Rmdir(name);
if e1 == 0 {
return nil;
}
// Both failed: figure out which error to return.
// OS X and Linux differ on whether unlink(dir)
// returns EISDIR, so can't use that. However,
// both agree that rmdir(file) returns ENOTDIR,
// so we can use that to decide which error is real.
// Rmdir might also return ENOTDIR if given a bad
// file path, like /etc/passwd/foo, but in that case,
// both errors will be ENOTDIR, so it's okay to
// use the error from unlink.
if e1 != syscall.ENOTDIR {
e = e1;
}
return &PathError{"remove", name, Errno(e)};
}
// LinkError records an error during a link or symlink
// system call and the paths that caused it.
type LinkError struct {
Op string;
Old string;
New string;
Error Error;
}
func (e *LinkError) String() string {
return e.Op + " " + e.Old + " " + e.New + ": " + e.Error.String();
}
// Link creates a hard link.
func Link(oldname, newname string) Error {
e := syscall.Link(oldname, newname);
if e != 0 {
return &LinkError{"link", oldname, newname, Errno(e)};
}
return nil;
}
// Symlink creates a symbolic link.
func Symlink(oldname, newname string) Error {
e := syscall.Symlink(oldname, newname);
if e != 0 {
return &LinkError{"symlink", oldname, newname, Errno(e)};
}
return nil;
}
// Readlink reads the contents of a symbolic link: the destination of
// the link. It returns the contents and an Error, if any.
func Readlink(name string) (string, Error) {
for len := 128; ; len *= 2 {
b := make([]byte, len);
n, e := syscall.Readlink(name, b);
if e != 0 {
return "", &PathError{"readlink", name, Errno(e)};
}
if n < len {
return string(b[0:n]), nil;
}
}
// Silence 6g.
return "", nil;
}
// Chmod changes the mode of the named file to mode.
// If the file is a symbolic link, it changes the uid and gid of the link's target.
func Chmod(name string, mode int) Error {
if e := syscall.Chmod(name, mode); e != 0 {
return &PathError{"chmod", name, Errno(e)};
}
return nil;
}
// Chmod changes the mode of the file to mode.
func (f *File) Chmod(mode int) Error {
if e := syscall.Fchmod(f.fd, mode); e != 0 {
return &PathError{"chmod", f.name, Errno(e)};
}
return nil;
}
// 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.
func Chown(name string, uid, gid int) Error {
if e := syscall.Chown(name, uid, gid); e != 0 {
return &PathError{"chown", name, Errno(e)};
}
return nil;
}
// 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.
func Lchown(name string, uid, gid int) Error {
if e := syscall.Lchown(name, uid, gid); e != 0 {
return &PathError{"lchown", name, Errno(e)};
}
return nil;
}
// Chown changes the numeric uid and gid of the named file.
func (f *File) Chown(uid, gid int) Error {
if e := syscall.Fchown(f.fd, uid, gid); e != 0 {
return &PathError{"chown", f.name, Errno(e)};
}
return nil;
}
// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
func Truncate(name string, size int64) Error {
if e := syscall.Truncate(name, size); e != 0 {
return &PathError{"truncate", name, Errno(e)};
}
return nil;
}
// Truncate changes the size of the file.
// It does not change the I/O offset.
func (f *File) Truncate(size int64) Error {
if e := syscall.Ftruncate(f.fd, size); e != 0 {
return &PathError{"truncate", f.name, Errno(e)};
}
return nil;
}