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go/doc/progs/file.go
Russ Cox c017a8299f syscall: use error
- syscall (not os) now defines the Errno type.
- the low-level assembly functions Syscall, Syscall6, and so on
  return Errno, not uintptr
- syscall wrappers all return error, not uintptr.

R=golang-dev, mikioh.mikioh, r, alex.brainman
CC=golang-dev
https://golang.org/cl/5372080
2011-11-13 22:44:52 -05:00

78 lines
1.5 KiB
Go

// 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.
package file
import (
"os"
"syscall"
)
type File struct {
fd int // file descriptor number
name string // file name at Open time
}
func newFile(fd int, name string) *File {
if fd < 0 {
return nil
}
return &File{fd, name}
}
var (
Stdin = newFile(syscall.Stdin, "/dev/stdin")
Stdout = newFile(syscall.Stdout, "/dev/stdout")
Stderr = newFile(syscall.Stderr, "/dev/stderr")
)
func OpenFile(name string, mode int, perm uint32) (file *File, err error) {
r, err := syscall.Open(name, mode, perm)
return newFile(r, name), err
}
const (
O_RDONLY = syscall.O_RDONLY
O_RDWR = syscall.O_RDWR
O_CREATE = syscall.O_CREAT
O_TRUNC = syscall.O_TRUNC
)
func Open(name string) (file *File, err error) {
return OpenFile(name, O_RDONLY, 0)
}
func Create(name string) (file *File, err error) {
return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
}
func (file *File) Close() error {
if file == nil {
return os.EINVAL
}
err := syscall.Close(file.fd)
file.fd = -1 // so it can't be closed again
return err
}
func (file *File) Read(b []byte) (ret int, err error) {
if file == nil {
return -1, os.EINVAL
}
r, err := syscall.Read(file.fd, b)
return int(r), err
}
func (file *File) Write(b []byte) (ret int, err error) {
if file == nil {
return -1, os.EINVAL
}
r, err := syscall.Write(file.fd, b)
return int(r), err
}
func (file *File) String() string {
return file.name
}