1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
// Copyright 2012 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 bytes
import (
"errors"
"io"
"unicode/utf8"
)
// A Reader implements the io.Reader, io.ReaderAt, io.WriterTo, io.Seeker,
// io.ByteScanner, and io.RuneScanner interfaces by reading from
// a byte slice.
// Unlike a Buffer, a Reader is read-only and supports seeking.
type Reader struct {
s []byte
i int // current reading index
prevRune int // index of previous rune; or < 0
}
// Len returns the number of bytes of the unread portion of the
// slice.
func (r *Reader) Len() int {
if r.i >= len(r.s) {
return 0
}
return len(r.s) - r.i
}
func (r *Reader) Read(b []byte) (n int, err error) {
if len(b) == 0 {
return 0, nil
}
if r.i >= len(r.s) {
return 0, io.EOF
}
n = copy(b, r.s[r.i:])
r.i += n
r.prevRune = -1
return
}
func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
if off < 0 {
return 0, errors.New("bytes: invalid offset")
}
if off >= int64(len(r.s)) {
return 0, io.EOF
}
n = copy(b, r.s[int(off):])
if n < len(b) {
err = io.EOF
}
return
}
func (r *Reader) ReadByte() (b byte, err error) {
if r.i >= len(r.s) {
return 0, io.EOF
}
b = r.s[r.i]
r.i++
r.prevRune = -1
return
}
func (r *Reader) UnreadByte() error {
if r.i <= 0 {
return errors.New("bytes.Reader: at beginning of slice")
}
r.i--
r.prevRune = -1
return nil
}
func (r *Reader) ReadRune() (ch rune, size int, err error) {
if r.i >= len(r.s) {
return 0, 0, io.EOF
}
r.prevRune = r.i
if c := r.s[r.i]; c < utf8.RuneSelf {
r.i++
return rune(c), 1, nil
}
ch, size = utf8.DecodeRune(r.s[r.i:])
r.i += size
return
}
func (r *Reader) UnreadRune() error {
if r.prevRune < 0 {
return errors.New("bytes.Reader: previous operation was not ReadRune")
}
r.i = r.prevRune
r.prevRune = -1
return nil
}
// Seek implements the io.Seeker interface.
func (r *Reader) Seek(offset int64, whence int) (int64, error) {
var abs int64
switch whence {
case 0:
abs = offset
case 1:
abs = int64(r.i) + offset
case 2:
abs = int64(len(r.s)) + offset
default:
return 0, errors.New("bytes: invalid whence")
}
if abs < 0 {
return 0, errors.New("bytes: negative position")
}
if abs >= 1<<31 {
return 0, errors.New("bytes: position out of range")
}
r.i = int(abs)
return abs, nil
}
// WriteTo implements the io.WriterTo interface.
func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
r.prevRune = -1
if r.i >= len(r.s) {
return 0, nil
}
b := r.s[r.i:]
m, err := w.Write(b)
if m > len(b) {
panic("bytes.Reader.WriteTo: invalid Write count")
}
r.i += m
n = int64(m)
if m != len(b) && err == nil {
err = io.ErrShortWrite
}
return
}
// NewReader returns a new Reader reading from b.
func NewReader(b []byte) *Reader { return &Reader{b, 0, -1} }
|
