1// Copyright 2015 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 bio implements common I/O abstractions used within the Go toolchain.
6package bio
7
8import (
9	"bufio"
10	"io"
11	"log"
12	"os"
13)
14
15// Reader implements a seekable buffered io.Reader.
16type Reader struct {
17	f *os.File
18	*bufio.Reader
19}
20
21// Writer implements a seekable buffered io.Writer.
22type Writer struct {
23	f *os.File
24	*bufio.Writer
25}
26
27// Create creates the file named name and returns a Writer
28// for that file.
29func Create(name string) (*Writer, error) {
30	f, err := os.Create(name)
31	if err != nil {
32		return nil, err
33	}
34	return &Writer{f: f, Writer: bufio.NewWriter(f)}, nil
35}
36
37// Open returns a Reader for the file named name.
38func Open(name string) (*Reader, error) {
39	f, err := os.Open(name)
40	if err != nil {
41		return nil, err
42	}
43	return NewReader(f), nil
44}
45
46// NewReader returns a Reader from an open file.
47func NewReader(f *os.File) *Reader {
48	return &Reader{f: f, Reader: bufio.NewReader(f)}
49}
50
51func (r *Reader) MustSeek(offset int64, whence int) int64 {
52	if whence == 1 {
53		offset -= int64(r.Buffered())
54	}
55	off, err := r.f.Seek(offset, whence)
56	if err != nil {
57		log.Fatalf("seeking in output: %v", err)
58	}
59	r.Reset(r.f)
60	return off
61}
62
63func (w *Writer) MustSeek(offset int64, whence int) int64 {
64	if err := w.Flush(); err != nil {
65		log.Fatalf("writing output: %v", err)
66	}
67	off, err := w.f.Seek(offset, whence)
68	if err != nil {
69		log.Fatalf("seeking in output: %v", err)
70	}
71	return off
72}
73
74func (r *Reader) Offset() int64 {
75	off, err := r.f.Seek(0, 1)
76	if err != nil {
77		log.Fatalf("seeking in output [0, 1]: %v", err)
78	}
79	off -= int64(r.Buffered())
80	return off
81}
82
83func (w *Writer) Offset() int64 {
84	if err := w.Flush(); err != nil {
85		log.Fatalf("writing output: %v", err)
86	}
87	off, err := w.f.Seek(0, 1)
88	if err != nil {
89		log.Fatalf("seeking in output [0, 1]: %v", err)
90	}
91	return off
92}
93
94func (r *Reader) Close() error {
95	return r.f.Close()
96}
97
98func (w *Writer) Close() error {
99	err := w.Flush()
100	err1 := w.f.Close()
101	if err == nil {
102		err = err1
103	}
104	return err
105}
106
107func (r *Reader) File() *os.File {
108	return r.f
109}
110
111func (w *Writer) File() *os.File {
112	return w.f
113}
114
115// Slice reads the next length bytes of r into a slice.
116//
117// This slice may be backed by mmap'ed memory. Currently, this memory
118// will never be unmapped. The second result reports whether the
119// backing memory is read-only.
120func (r *Reader) Slice(length uint64) ([]byte, bool, error) {
121	if length == 0 {
122		return []byte{}, false, nil
123	}
124
125	data, ok := r.sliceOS(length)
126	if ok {
127		return data, true, nil
128	}
129
130	data = make([]byte, length)
131	_, err := io.ReadFull(r, data)
132	if err != nil {
133		return nil, false, err
134	}
135	return data, false, nil
136}
137
138// SliceRO returns a slice containing the next length bytes of r
139// backed by a read-only mmap'd data. If the mmap cannot be
140// established (limit exceeded, region too small, etc) a nil slice
141// will be returned. If mmap succeeds, it will never be unmapped.
142func (r *Reader) SliceRO(length uint64) []byte {
143	data, ok := r.sliceOS(length)
144	if ok {
145		return data
146	}
147	return nil
148}
149