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Source file
src/strings/reader.go
Documentation: strings
1
2
3
4
5 package strings
6
7 import (
8 "errors"
9 "io"
10 "unicode/utf8"
11 )
12
13
14
15
16 type Reader struct {
17 s string
18 i int64
19 prevRune int
20 }
21
22
23
24 func (r *Reader) Len() int {
25 if r.i >= int64(len(r.s)) {
26 return 0
27 }
28 return int(int64(len(r.s)) - r.i)
29 }
30
31
32
33
34
35 func (r *Reader) Size() int64 { return int64(len(r.s)) }
36
37 func (r *Reader) Read(b []byte) (n int, err error) {
38 if r.i >= int64(len(r.s)) {
39 return 0, io.EOF
40 }
41 r.prevRune = -1
42 n = copy(b, r.s[r.i:])
43 r.i += int64(n)
44 return
45 }
46
47 func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
48
49 if off < 0 {
50 return 0, errors.New("strings.Reader.ReadAt: negative offset")
51 }
52 if off >= int64(len(r.s)) {
53 return 0, io.EOF
54 }
55 n = copy(b, r.s[off:])
56 if n < len(b) {
57 err = io.EOF
58 }
59 return
60 }
61
62 func (r *Reader) ReadByte() (byte, error) {
63 r.prevRune = -1
64 if r.i >= int64(len(r.s)) {
65 return 0, io.EOF
66 }
67 b := r.s[r.i]
68 r.i++
69 return b, nil
70 }
71
72 func (r *Reader) UnreadByte() error {
73 r.prevRune = -1
74 if r.i <= 0 {
75 return errors.New("strings.Reader.UnreadByte: at beginning of string")
76 }
77 r.i--
78 return nil
79 }
80
81 func (r *Reader) ReadRune() (ch rune, size int, err error) {
82 if r.i >= int64(len(r.s)) {
83 r.prevRune = -1
84 return 0, 0, io.EOF
85 }
86 r.prevRune = int(r.i)
87 if c := r.s[r.i]; c < utf8.RuneSelf {
88 r.i++
89 return rune(c), 1, nil
90 }
91 ch, size = utf8.DecodeRuneInString(r.s[r.i:])
92 r.i += int64(size)
93 return
94 }
95
96 func (r *Reader) UnreadRune() error {
97 if r.prevRune < 0 {
98 return errors.New("strings.Reader.UnreadRune: previous operation was not ReadRune")
99 }
100 r.i = int64(r.prevRune)
101 r.prevRune = -1
102 return nil
103 }
104
105
106 func (r *Reader) Seek(offset int64, whence int) (int64, error) {
107 r.prevRune = -1
108 var abs int64
109 switch whence {
110 case io.SeekStart:
111 abs = offset
112 case io.SeekCurrent:
113 abs = r.i + offset
114 case io.SeekEnd:
115 abs = int64(len(r.s)) + offset
116 default:
117 return 0, errors.New("strings.Reader.Seek: invalid whence")
118 }
119 if abs < 0 {
120 return 0, errors.New("strings.Reader.Seek: negative position")
121 }
122 r.i = abs
123 return abs, nil
124 }
125
126
127 func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
128 r.prevRune = -1
129 if r.i >= int64(len(r.s)) {
130 return 0, nil
131 }
132 s := r.s[r.i:]
133 m, err := io.WriteString(w, s)
134 if m > len(s) {
135 panic("strings.Reader.WriteTo: invalid WriteString count")
136 }
137 r.i += int64(m)
138 n = int64(m)
139 if m != len(s) && err == nil {
140 err = io.ErrShortWrite
141 }
142 return
143 }
144
145
146 func (r *Reader) Reset(s string) { *r = Reader{s, 0, -1} }
147
148
149
150 func NewReader(s string) *Reader { return &Reader{s, 0, -1} }
151
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