299 lines
8.4 KiB
Go
299 lines
8.4 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build darwin freebsd linux netbsd openbsd
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package os
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import (
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"runtime"
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"syscall"
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)
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// File represents an open file descriptor.
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type File struct {
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*file
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}
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// file is the real representation of *File.
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// The extra level of indirection ensures that no clients of os
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// can overwrite this data, which could cause the finalizer
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// to close the wrong file descriptor.
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type file struct {
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fd int
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name string
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dirinfo *dirInfo // nil unless directory being read
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nepipe int // number of consecutive EPIPE in Write
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}
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// Fd returns the integer Unix file descriptor referencing the open file.
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func (f *File) Fd() uintptr {
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if f == nil {
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return ^(uintptr(0))
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}
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return uintptr(f.fd)
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}
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// NewFile returns a new File with the given file descriptor and name.
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func NewFile(fd uintptr, name string) *File {
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fdi := int(fd)
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if fdi < 0 {
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return nil
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}
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f := &File{&file{fd: fdi, name: name}}
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runtime.SetFinalizer(f.file, (*file).close)
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return f
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}
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// Auxiliary information if the File describes a directory
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type dirInfo struct {
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buf []byte // buffer for directory I/O
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dir *syscall.DIR // from opendir
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}
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// DevNull is the name of the operating system's ``null device.''
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// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
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const DevNull = "/dev/null"
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// OpenFile is the generalized open call; most users will use Open
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// or Create instead. It opens the named file with specified flag
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// (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful,
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// methods on the returned File can be used for I/O.
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// If there is an error, it will be of type *PathError.
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func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {
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r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
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if e != nil {
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return nil, &PathError{"open", name, e}
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}
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// There's a race here with fork/exec, which we are
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// content to live with. See ../syscall/exec_unix.go.
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// On OS X 10.6, the O_CLOEXEC flag is not respected.
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// On OS X 10.7, the O_CLOEXEC flag works.
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// Without a cheap & reliable way to detect 10.6 vs 10.7 at
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// runtime, we just always call syscall.CloseOnExec on Darwin.
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// Once >=10.7 is prevalent, this extra call can removed.
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if syscall.O_CLOEXEC == 0 || runtime.GOOS == "darwin" { // O_CLOEXEC not supported
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syscall.CloseOnExec(r)
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}
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return NewFile(uintptr(r), name), nil
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}
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// Close closes the File, rendering it unusable for I/O.
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// It returns an error, if any.
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func (f *File) Close() error {
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return f.file.close()
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}
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func (file *file) close() error {
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if file == nil || file.fd < 0 {
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return syscall.EINVAL
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}
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var err error
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if e := syscall.Close(file.fd); e != nil {
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err = &PathError{"close", file.name, e}
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}
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if file.dirinfo != nil {
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if libc_closedir(file.dirinfo.dir) < 0 && err == nil {
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err = &PathError{"closedir", file.name, syscall.GetErrno()}
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}
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}
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file.fd = -1 // so it can't be closed again
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// no need for a finalizer anymore
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runtime.SetFinalizer(file, nil)
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return err
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}
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// Stat returns the FileInfo structure describing file.
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// If there is an error, it will be of type *PathError.
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func (f *File) Stat() (fi FileInfo, err error) {
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var stat syscall.Stat_t
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err = syscall.Fstat(f.fd, &stat)
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if err != nil {
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return nil, &PathError{"stat", f.name, err}
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}
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return fileInfoFromStat(&stat, f.name), nil
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}
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// Stat returns a FileInfo describing the named file.
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// If there is an error, it will be of type *PathError.
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func Stat(name string) (fi FileInfo, err error) {
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var stat syscall.Stat_t
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err = syscall.Stat(name, &stat)
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if err != nil {
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return nil, &PathError{"stat", name, err}
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}
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return fileInfoFromStat(&stat, name), nil
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}
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// Lstat returns a FileInfo describing the named file.
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// If the file is a symbolic link, the returned FileInfo
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// describes the symbolic link. Lstat makes no attempt to follow the link.
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// If there is an error, it will be of type *PathError.
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func Lstat(name string) (fi FileInfo, err error) {
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var stat syscall.Stat_t
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err = syscall.Lstat(name, &stat)
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if err != nil {
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return nil, &PathError{"lstat", name, err}
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}
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return fileInfoFromStat(&stat, name), nil
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}
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func (f *File) readdir(n int) (fi []FileInfo, err error) {
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dirname := f.name
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if dirname == "" {
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dirname = "."
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}
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dirname += "/"
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names, err := f.Readdirnames(n)
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fi = make([]FileInfo, len(names))
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for i, filename := range names {
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fip, err := Lstat(dirname + filename)
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if err == nil {
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fi[i] = fip
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} else {
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fi[i] = &fileStat{name: filename}
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}
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}
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return fi, err
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}
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// read reads up to len(b) bytes from the File.
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// It returns the number of bytes read and an error, if any.
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func (f *File) read(b []byte) (n int, err error) {
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return syscall.Read(f.fd, b)
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}
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// pread reads len(b) bytes from the File starting at byte offset off.
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// It returns the number of bytes read and the error, if any.
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// EOF is signaled by a zero count with err set to 0.
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func (f *File) pread(b []byte, off int64) (n int, err error) {
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return syscall.Pread(f.fd, b, off)
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}
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// write writes len(b) bytes to the File.
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// It returns the number of bytes written and an error, if any.
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func (f *File) write(b []byte) (n int, err error) {
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for {
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m, err := syscall.Write(f.fd, b)
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n += m
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// If the syscall wrote some data but not all (short write)
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// or it returned EINTR, then assume it stopped early for
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// reasons that are uninteresting to the caller, and try again.
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if 0 < m && m < len(b) || err == syscall.EINTR {
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b = b[m:]
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continue
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}
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return n, err
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}
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panic("not reached")
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}
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// pwrite writes len(b) bytes to the File starting at byte offset off.
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// It returns the number of bytes written and an error, if any.
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func (f *File) pwrite(b []byte, off int64) (n int, err error) {
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return syscall.Pwrite(f.fd, b, off)
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}
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// seek sets the offset for the next Read or Write on file to offset, interpreted
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// according to whence: 0 means relative to the origin of the file, 1 means
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// relative to the current offset, and 2 means relative to the end.
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// It returns the new offset and an error, if any.
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func (f *File) seek(offset int64, whence int) (ret int64, err error) {
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return syscall.Seek(f.fd, offset, whence)
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}
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// Truncate changes the size of the named file.
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// If the file is a symbolic link, it changes the size of the link's target.
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// If there is an error, it will be of type *PathError.
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func Truncate(name string, size int64) error {
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if e := syscall.Truncate(name, size); e != nil {
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return &PathError{"truncate", name, e}
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}
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return nil
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}
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// Remove removes the named file or directory.
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// If there is an error, it will be of type *PathError.
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func Remove(name string) error {
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// System call interface forces us to know
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// whether name is a file or directory.
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// Try both: it is cheaper on average than
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// doing a Stat plus the right one.
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e := syscall.Unlink(name)
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if e == nil {
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return nil
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}
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e1 := syscall.Rmdir(name)
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if e1 == nil {
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return nil
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}
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// Both failed: figure out which error to return.
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// OS X and Linux differ on whether unlink(dir)
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// returns EISDIR, so can't use that. However,
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// both agree that rmdir(file) returns ENOTDIR,
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// so we can use that to decide which error is real.
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// Rmdir might also return ENOTDIR if given a bad
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// file path, like /etc/passwd/foo, but in that case,
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// both errors will be ENOTDIR, so it's okay to
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// use the error from unlink.
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if e1 != syscall.ENOTDIR {
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e = e1
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}
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return &PathError{"remove", name, e}
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}
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// basename removes trailing slashes and the leading directory name from path name
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func basename(name string) string {
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i := len(name) - 1
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// Remove trailing slashes
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for ; i > 0 && name[i] == '/'; i-- {
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name = name[:i]
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}
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// Remove leading directory name
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for i--; i >= 0; i-- {
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if name[i] == '/' {
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name = name[i+1:]
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break
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}
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}
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return name
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}
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// Pipe returns a connected pair of Files; reads from r return bytes written to w.
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// It returns the files and an error, if any.
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func Pipe() (r *File, w *File, err error) {
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var p [2]int
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// See ../syscall/exec.go for description of lock.
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syscall.ForkLock.RLock()
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e := syscall.Pipe(p[0:])
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if e != nil {
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syscall.ForkLock.RUnlock()
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return nil, nil, NewSyscallError("pipe", e)
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}
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syscall.CloseOnExec(p[0])
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syscall.CloseOnExec(p[1])
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syscall.ForkLock.RUnlock()
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return NewFile(uintptr(p[0]), "|0"), NewFile(uintptr(p[1]), "|1"), nil
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}
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// TempDir returns the default directory to use for temporary files.
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func TempDir() string {
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dir := Getenv("TMPDIR")
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if dir == "" {
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dir = "/tmp"
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}
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return dir
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}
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