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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.
// +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.
// 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.
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 fixCount(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 fixCount(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 := fixCount(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 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 {
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 == "" {
if runtime.GOOS == "android" {
dir = "/data/local/tmp"
} else {
dir = "/tmp"
}
}
return dir
}
// 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 {
e := syscall.Link(oldname, newname)
if e != nil {
return &LinkError{"link", oldname, newname, e}
}
return nil
}
// 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 {
e := syscall.Symlink(oldname, newname)
if e != nil {
return &LinkError{"symlink", oldname, newname, e}
}
return nil
}