Source file doc/progs/file.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package file
     6	
     7	import (
     8		"os"
     9		"syscall"
    10	)
    11	
    12	type File struct {
    13		fd   int    // file descriptor number
    14		name string // file name at Open time
    15	}
    16	
    17	func newFile(fd int, name string) *File {
    18		if fd < 0 {
    19			return nil
    20		}
    21		return &File{fd, name}
    22	}
    23	
    24	var (
    25		Stdin  = newFile(syscall.Stdin, "/dev/stdin")
    26		Stdout = newFile(syscall.Stdout, "/dev/stdout")
    27		Stderr = newFile(syscall.Stderr, "/dev/stderr")
    28	)
    29	
    30	func OpenFile(name string, mode int, perm uint32) (file *File, err os.Error) {
    31		r, e := syscall.Open(name, mode, perm)
    32		if e != 0 {
    33			err = os.Errno(e)
    34		}
    35		return newFile(r, name), err
    36	}
    37	
    38	const (
    39		O_RDONLY = syscall.O_RDONLY
    40		O_RDWR   = syscall.O_RDWR
    41		O_CREATE = syscall.O_CREAT
    42		O_TRUNC  = syscall.O_TRUNC
    43	)
    44	
    45	func Open(name string) (file *File, err os.Error) {
    46		return OpenFile(name, O_RDONLY, 0)
    47	}
    48	
    49	func Create(name string) (file *File, err os.Error) {
    50		return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
    51	}
    52	
    53	func (file *File) Close() os.Error {
    54		if file == nil {
    55			return os.EINVAL
    56		}
    57		e := syscall.Close(file.fd)
    58		file.fd = -1 // so it can't be closed again
    59		if e != 0 {
    60			return os.Errno(e)
    61		}
    62		return nil
    63	}
    64	
    65	func (file *File) Read(b []byte) (ret int, err os.Error) {
    66		if file == nil {
    67			return -1, os.EINVAL
    68		}
    69		r, e := syscall.Read(file.fd, b)
    70		if e != 0 {
    71			err = os.Errno(e)
    72		}
    73		return int(r), err
    74	}
    75	
    76	func (file *File) Write(b []byte) (ret int, err os.Error) {
    77		if file == nil {
    78			return -1, os.EINVAL
    79		}
    80		r, e := syscall.Write(file.fd, b)
    81		if e != 0 {
    82			err = os.Errno(e)
    83		}
    84		return int(r), err
    85	}
    86	
    87	func (file *File) String() string {
    88		return file.name
    89	}
The Go Programming Language

Source file doc/progs/file.go
