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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
// 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.
// The zero value for Reader operates like a Reader of an empty slice.
type Reader struct {
s []byte
i int64 // 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 >= int64(len(r.s)) {
return 0
}
return int(int64(len(r.s)) - r.i)
}
// Size returns the original length of the underlying byte slice.
// Size is the number of bytes available for reading via ReadAt.
// The result is unaffected by any method calls except Reset.
func (r *Reader) Size() int64 { return int64(len(r.s)) }
// Read implements the io.Reader interface.
func (r *Reader) Read(b []byte) (n int, err error) {
if r.i >= int64(len(r.s)) {
return 0, io.EOF
}
r.prevRune = -1
n = copy(b, r.s[r.i:])
r.i += int64(n)
return
}
// ReadAt implements the io.ReaderAt interface.
func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
// cannot modify state - see io.ReaderAt
if off < 0 {
return 0, errors.New("bytes.Reader.ReadAt: negative offset")
}
if off >= int64(len(r.s)) {
return 0, io.EOF
}
n = copy(b, r.s[off:])
if n < len(b) {
err = io.EOF
}
return
}
// ReadByte implements the io.ByteReader interface.
func (r *Reader) ReadByte() (byte, error) {
r.prevRune = -1
if r.i >= int64(len(r.s)) {
return 0, io.EOF
}
b := r.s[r.i]
r.i++
return b, nil
}
// UnreadByte complements ReadByte in implementing the io.ByteScanner interface.
func (r *Reader) UnreadByte() error {
if r.i <= 0 {
return errors.New("bytes.Reader.UnreadByte: at beginning of slice")
}
r.prevRune = -1
r.i--
return nil
}
// ReadRune implements the io.RuneReader interface.
func (r *Reader) ReadRune() (ch rune, size int, err error) {
if r.i >= int64(len(r.s)) {
r.prevRune = -1
return 0, 0, io.EOF
}
r.prevRune = int(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 += int64(size)
return
}
// UnreadRune complements ReadRune in implementing the io.RuneScanner interface.
func (r *Reader) UnreadRune() error {
if r.i <= 0 {
return errors.New("bytes.Reader.UnreadRune: at beginning of slice")
}
if r.prevRune < 0 {
return errors.New("bytes.Reader.UnreadRune: previous operation was not ReadRune")
}
r.i = int64(r.prevRune)
r.prevRune = -1
return nil
}
// Seek implements the io.Seeker interface.
func (r *Reader) Seek(offset int64, whence int) (int64, error) {
r.prevRune = -1
var abs int64
switch whence {
case io.SeekStart:
abs = offset
case io.SeekCurrent:
abs = r.i + offset
case io.SeekEnd:
abs = int64(len(r.s)) + offset
default:
return 0, errors.New("bytes.Reader.Seek: invalid whence")
}
if abs < 0 {
return 0, errors.New("bytes.Reader.Seek: negative position")
}
r.i = 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 >= int64(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 += int64(m)
n = int64(m)
if m != len(b) && err == nil {
err = io.ErrShortWrite
}
return
}
// Reset resets the Reader to be reading from b.
func (r *Reader) Reset(b []byte) { *r = Reader{b, 0, -1} }
// NewReader returns a new Reader reading from b.
func NewReader(b []byte) *Reader { return &Reader{b, 0, -1} }
|
