src/pkg/os/file_unix.go - go - Git at Google

 // 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.

 // +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris

 package os

 import (
 	"runtime"
 	"sync/atomic"
 	"syscall"
 )

 // File represents an open file descriptor.
 type File struct {
 	*file
 }

 // 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
 	nepipe  int32    // number of consecutive EPIPE in Write
 }

 // Fd returns the integer Unix file descriptor referencing the open file.
 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.
 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  []byte // buffer for directory I/O
 	nbuf int    // length of buf; return value from Getdirentries
 	bufp int    // location of next record in buf.
 }

 func epipecheck(file *File, e error) {
 	if e == syscall.EPIPE {
 		if atomic.AddInt32(&file.nepipe, 1) >= 10 {
 			sigpipe()
 		}
 	} else {
 		atomic.StoreInt32(&file.nepipe, 0)
 	}
 }

 // 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"

 // 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 *File, err error) {
 	r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
 	if e != nil {
 		return nil, &PathError{"open", name, e}
 	}

 	// There's a race here with fork/exec, which we are
 	// content to live with.  See ../syscall/exec_unix.go.
 	if !supportsCloseOnExec {
 		syscall.CloseOnExec(r)
 	}

 	return NewFile(uintptr(r), name), nil
 }

 // Close closes the File, rendering it unusable for I/O.
 // It returns an error, if any.
 func (f *File) Close() error {
 	if f == nil {
 		return ErrInvalid
 	}
 	return f.file.close()
 }

 func (file *file) close() error {
 	if file == nil || file.fd < 0 {
 		return syscall.EINVAL
 	}
 	var err error
 	if e := syscall.Close(file.fd); e != nil {
 		err = &PathError{"close", file.name, e}
 	}
 	file.fd = -1 // 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() (fi FileInfo, err error) {
 	if f == nil {
 		return nil, ErrInvalid
 	}
 	var stat syscall.Stat_t
 	err = syscall.Fstat(f.fd, &stat)
 	if err != nil {
 		return nil, &PathError{"stat", f.name, err}
 	}
 	return fileInfoFromStat(&stat, f.name), nil
 }

 // Stat returns a FileInfo describing the named file.
 // If there is an error, it will be of type *PathError.
 func Stat(name string) (fi FileInfo, err error) {
 	var stat syscall.Stat_t
 	err = syscall.Stat(name, &stat)
 	if err != nil {
 		return nil, &PathError{"stat", name, err}
 	}
 	return fileInfoFromStat(&stat, name), nil
 }

 // Lstat returns a FileInfo describing the named file.
 // If the file is a symbolic link, the returned FileInfo
 // describes the symbolic link.  Lstat makes no attempt to follow the link.
 // If there is an error, it will be of type *PathError.
 func Lstat(name string) (fi FileInfo, err error) {
 	var stat syscall.Stat_t
 	err = syscall.Lstat(name, &stat)
 	if err != nil {
 		return nil, &PathError{"lstat", name, err}
 	}
 	return fileInfoFromStat(&stat, name), nil
 }

 func (f *File) readdir(n int) (fi []FileInfo, err error) {
 	dirname := f.name
 	if dirname == "" {
 		dirname = "."
 	}
 	names, err := f.Readdirnames(n)
 	fi = make([]FileInfo, 0, len(names))
 	for _, filename := range names {
 		fip, lerr := lstat(dirname + "/" + filename)
 		if IsNotExist(lerr) {
 			// File disappeared between readdir + stat.
 			// Just treat it as if it didn't exist.
 			continue
 		}
 		if lerr != nil {
 			return fi, lerr
 		}
 		fi = append(fi, fip)
 	}
 	return fi, err
 }

 // Darwin and FreeBSD can't read or write 2GB+ at a time,
 // even on 64-bit systems. See golang.org/issue/7812.
 // Use 1GB instead of, say, 2GB-1, to keep subsequent
 // reads aligned.
 const (
 	needsMaxRW = runtime.GOOS == "darwin" || runtime.GOOS == "freebsd"
 	maxRW      = 1 << 30
 )

 // 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) {
 	if needsMaxRW && len(b) > maxRW {
 		b = b[:maxRW]
 	}
 	return syscall.Read(f.fd, b)
 }

 // 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) {
 	if needsMaxRW && len(b) > maxRW {
 		b = b[:maxRW]
 	}
 	return syscall.Pread(f.fd, b, off)
 }

 // write writes len(b) bytes to the File.
 // It returns the number of bytes written and an error, if any.
 func (f *File) write(b []byte) (n int, err error) {
 	for {
 		bcap := b
 		if needsMaxRW && len(bcap) > maxRW {
 			bcap = bcap[:maxRW]
 		}
 		m, err := syscall.Write(f.fd, bcap)
 		n += m

 		// If the syscall wrote some data but not all (short write)
 		// or it returned EINTR, then assume it stopped early for
 		// reasons that are uninteresting to the caller, and try again.
 		if 0 < m && m < len(bcap) || err == syscall.EINTR {
 			b = b[m:]
 			continue
 		}

 		if needsMaxRW && len(bcap) != len(b) && err == nil {
 			b = b[m:]
 			continue
 		}

 		return n, err
 	}
 }

 // 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.
 func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 	if needsMaxRW && len(b) > maxRW {
 		b = b[:maxRW]
 	}
 	return 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 {
 	if e := syscall.Truncate(name, size); e != nil {
 		return &PathError{"truncate", name, e}
 	}
 	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 {
 	// 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 == nil {
 		return nil
 	}
 	e1 := syscall.Rmdir(name)
 	if e1 == nil {
 		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, e}
 }

 // basename removes trailing slashes and the leading directory name from path name
 func basename(name string) string {
 	i := len(name) - 1
 	// Remove trailing slashes
 	for ; i > 0 && name[i] == '/'; i-- {
 		name = name[:i]
 	}
 	// Remove leading directory name
 	for i--; i >= 0; i-- {
 		if name[i] == '/' {
 			name = name[i+1:]
 			break
 		}
 	}

 	return name
 }

 // TempDir returns the default directory to use for temporary files.
 func TempDir() string {
 	dir := Getenv("TMPDIR")
 	if dir == "" {
 		dir = "/tmp"
 	}
 	return dir
 }
	// 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.

	// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris

	package os

	import (
	"runtime"
	"sync/atomic"
	"syscall"
	)

	// File represents an open file descriptor.
	type File struct {
	*file
	}

	// 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
	nepipe int32 // number of consecutive EPIPE in Write
	}

	// Fd returns the integer Unix file descriptor referencing the open file.
	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.
	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 []byte // buffer for directory I/O
	nbuf int // length of buf; return value from Getdirentries
	bufp int // location of next record in buf.
	}

	func epipecheck(file *File, e error) {
	if e == syscall.EPIPE {
	if atomic.AddInt32(&file.nepipe, 1) >= 10 {
	sigpipe()
	}
	} else {
	atomic.StoreInt32(&file.nepipe, 0)
	}
	}

	// 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"

	// 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 *File, err error) {
	r, e := syscall.Open(name, flag\|syscall.O_CLOEXEC, syscallMode(perm))
	if e != nil {
	return nil, &PathError{"open", name, e}
	}

	// There's a race here with fork/exec, which we are
	// content to live with. See ../syscall/exec_unix.go.
	if !supportsCloseOnExec {
	syscall.CloseOnExec(r)
	}

	return NewFile(uintptr(r), name), nil
	}

	// Close closes the File, rendering it unusable for I/O.
	// It returns an error, if any.
	func (f *File) Close() error {
	if f == nil {
	return ErrInvalid
	}
	return f.file.close()
	}

	func (file *file) close() error {
	if file == nil \|\| file.fd < 0 {
	return syscall.EINVAL
	}
	var err error
	if e := syscall.Close(file.fd); e != nil {
	err = &PathError{"close", file.name, e}
	}
	file.fd = -1 // 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() (fi FileInfo, err error) {
	if f == nil {
	return nil, ErrInvalid
	}
	var stat syscall.Stat_t
	err = syscall.Fstat(f.fd, &stat)
	if err != nil {
	return nil, &PathError{"stat", f.name, err}
	}
	return fileInfoFromStat(&stat, f.name), nil
	}

	// Stat returns a FileInfo describing the named file.
	// If there is an error, it will be of type *PathError.
	func Stat(name string) (fi FileInfo, err error) {
	var stat syscall.Stat_t
	err = syscall.Stat(name, &stat)
	if err != nil {
	return nil, &PathError{"stat", name, err}
	}
	return fileInfoFromStat(&stat, name), nil
	}

	// Lstat returns a FileInfo describing the named file.
	// If the file is a symbolic link, the returned FileInfo
	// describes the symbolic link. Lstat makes no attempt to follow the link.
	// If there is an error, it will be of type *PathError.
	func Lstat(name string) (fi FileInfo, err error) {
	var stat syscall.Stat_t
	err = syscall.Lstat(name, &stat)
	if err != nil {
	return nil, &PathError{"lstat", name, err}
	}
	return fileInfoFromStat(&stat, name), nil
	}

	func (f *File) readdir(n int) (fi []FileInfo, err error) {
	dirname := f.name
	if dirname == "" {
	dirname = "."
	}
	names, err := f.Readdirnames(n)
	fi = make([]FileInfo, 0, len(names))
	for _, filename := range names {
	fip, lerr := lstat(dirname + "/" + filename)
	if IsNotExist(lerr) {
	// File disappeared between readdir + stat.
	// Just treat it as if it didn't exist.
	continue
	}
	if lerr != nil {
	return fi, lerr
	}
	fi = append(fi, fip)
	}
	return fi, err
	}

	// Darwin and FreeBSD can't read or write 2GB+ at a time,
	// even on 64-bit systems. See golang.org/issue/7812.
	// Use 1GB instead of, say, 2GB-1, to keep subsequent
	// reads aligned.
	const (
	needsMaxRW = runtime.GOOS == "darwin" \|\| runtime.GOOS == "freebsd"
	maxRW = 1 << 30
	)

	// 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) {
	if needsMaxRW && len(b) > maxRW {
	b = b[:maxRW]
	}
	return syscall.Read(f.fd, b)
	}

	// 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) {
	if needsMaxRW && len(b) > maxRW {
	b = b[:maxRW]
	}
	return syscall.Pread(f.fd, b, off)
	}

	// write writes len(b) bytes to the File.
	// It returns the number of bytes written and an error, if any.
	func (f *File) write(b []byte) (n int, err error) {
	for {
	bcap := b
	if needsMaxRW && len(bcap) > maxRW {
	bcap = bcap[:maxRW]
	}
	m, err := syscall.Write(f.fd, bcap)
	n += m

	// If the syscall wrote some data but not all (short write)
	// or it returned EINTR, then assume it stopped early for
	// reasons that are uninteresting to the caller, and try again.
	if 0 < m && m < len(bcap) \|\| err == syscall.EINTR {
	b = b[m:]
	continue
	}

	if needsMaxRW && len(bcap) != len(b) && err == nil {
	b = b[m:]
	continue
	}

	return n, err
	}
	}

	// 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.
	func (f *File) pwrite(b []byte, off int64) (n int, err error) {
	if needsMaxRW && len(b) > maxRW {
	b = b[:maxRW]
	}
	return 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 {
	if e := syscall.Truncate(name, size); e != nil {
	return &PathError{"truncate", name, e}
	}
	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 {
	// 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 == nil {
	return nil
	}
	e1 := syscall.Rmdir(name)
	if e1 == nil {
	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, e}
	}

	// basename removes trailing slashes and the leading directory name from path name
	func basename(name string) string {
	i := len(name) - 1
	// Remove trailing slashes
	for ; i > 0 && name[i] == '/'; i-- {
	name = name[:i]
	}
	// Remove leading directory name
	for i--; i >= 0; i-- {
	if name[i] == '/' {
	name = name[i+1:]
	break
	}
	}

	return name
	}

	// TempDir returns the default directory to use for temporary files.
	func TempDir() string {
	dir := Getenv("TMPDIR")
	if dir == "" {
	dir = "/tmp"
	}
	return dir
	}