big5.go raw
1 // Copyright 2013 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 traditionalchinese
6
7 import (
8 "unicode/utf8"
9
10 "golang.org/x/text/encoding"
11 "golang.org/x/text/encoding/internal"
12 "golang.org/x/text/encoding/internal/identifier"
13 "golang.org/x/text/transform"
14 )
15
16 // All is a list of all defined encodings in this package.
17 var All = []encoding.Encoding{Big5}
18
19 // Big5 is the Big5 encoding, also known as Code Page 950.
20 var Big5 encoding.Encoding = &big5
21
22 var big5 = internal.Encoding{
23 Encoding: &internal.SimpleEncoding{Decoder: big5Decoder{}, Encoder: big5Encoder{}},
24 Name: "Big5",
25 MIB: identifier.Big5,
26 }
27
28 type big5Decoder struct{ transform.NopResetter }
29
30 func (big5Decoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
31 r, size, s := rune(0), 0, ""
32 loop:
33 for ; nSrc < len(src); nSrc += size {
34 switch c0 := src[nSrc]; {
35 case c0 < utf8.RuneSelf:
36 r, size = rune(c0), 1
37
38 case 0x81 <= c0 && c0 < 0xff:
39 if nSrc+1 >= len(src) {
40 if !atEOF {
41 err = transform.ErrShortSrc
42 break loop
43 }
44 r, size = utf8.RuneError, 1
45 goto write
46 }
47 c1 := src[nSrc+1]
48 switch {
49 case 0x40 <= c1 && c1 < 0x7f:
50 c1 -= 0x40
51 case 0xa1 <= c1 && c1 < 0xff:
52 c1 -= 0x62
53 case c1 < 0x40:
54 r, size = utf8.RuneError, 1
55 goto write
56 default:
57 r, size = utf8.RuneError, 2
58 goto write
59 }
60 r, size = '\ufffd', 2
61 if i := int(c0-0x81)*157 + int(c1); i < len(decode) {
62 if 1133 <= i && i < 1167 {
63 // The two-rune special cases for LATIN CAPITAL / SMALL E WITH CIRCUMFLEX
64 // AND MACRON / CARON are from http://encoding.spec.whatwg.org/#big5
65 switch i {
66 case 1133:
67 s = "\u00CA\u0304"
68 goto writeStr
69 case 1135:
70 s = "\u00CA\u030C"
71 goto writeStr
72 case 1164:
73 s = "\u00EA\u0304"
74 goto writeStr
75 case 1166:
76 s = "\u00EA\u030C"
77 goto writeStr
78 }
79 }
80 r = rune(decode[i])
81 if r == 0 {
82 r = '\ufffd'
83 }
84 }
85
86 default:
87 r, size = utf8.RuneError, 1
88 }
89
90 write:
91 if nDst+utf8.RuneLen(r) > len(dst) {
92 err = transform.ErrShortDst
93 break loop
94 }
95 nDst += utf8.EncodeRune(dst[nDst:], r)
96 continue loop
97
98 writeStr:
99 if nDst+len(s) > len(dst) {
100 err = transform.ErrShortDst
101 break loop
102 }
103 nDst += copy(dst[nDst:], s)
104 continue loop
105 }
106 return nDst, nSrc, err
107 }
108
109 type big5Encoder struct{ transform.NopResetter }
110
111 func (big5Encoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
112 r, size := rune(0), 0
113 for ; nSrc < len(src); nSrc += size {
114 r = rune(src[nSrc])
115
116 // Decode a 1-byte rune.
117 if r < utf8.RuneSelf {
118 size = 1
119 if nDst >= len(dst) {
120 err = transform.ErrShortDst
121 break
122 }
123 dst[nDst] = uint8(r)
124 nDst++
125 continue
126
127 } else {
128 // Decode a multi-byte rune.
129 r, size = utf8.DecodeRune(src[nSrc:])
130 if size == 1 {
131 // All valid runes of size 1 (those below utf8.RuneSelf) were
132 // handled above. We have invalid UTF-8 or we haven't seen the
133 // full character yet.
134 if !atEOF && !utf8.FullRune(src[nSrc:]) {
135 err = transform.ErrShortSrc
136 break
137 }
138 }
139 }
140
141 if r >= utf8.RuneSelf {
142 // func init checks that the switch covers all tables.
143 switch {
144 case encode0Low <= r && r < encode0High:
145 if r = rune(encode0[r-encode0Low]); r != 0 {
146 goto write2
147 }
148 case encode1Low <= r && r < encode1High:
149 if r = rune(encode1[r-encode1Low]); r != 0 {
150 goto write2
151 }
152 case encode2Low <= r && r < encode2High:
153 if r = rune(encode2[r-encode2Low]); r != 0 {
154 goto write2
155 }
156 case encode3Low <= r && r < encode3High:
157 if r = rune(encode3[r-encode3Low]); r != 0 {
158 goto write2
159 }
160 case encode4Low <= r && r < encode4High:
161 if r = rune(encode4[r-encode4Low]); r != 0 {
162 goto write2
163 }
164 case encode5Low <= r && r < encode5High:
165 if r = rune(encode5[r-encode5Low]); r != 0 {
166 goto write2
167 }
168 case encode6Low <= r && r < encode6High:
169 if r = rune(encode6[r-encode6Low]); r != 0 {
170 goto write2
171 }
172 case encode7Low <= r && r < encode7High:
173 if r = rune(encode7[r-encode7Low]); r != 0 {
174 goto write2
175 }
176 }
177 err = internal.ErrASCIIReplacement
178 break
179 }
180
181 write2:
182 if nDst+2 > len(dst) {
183 err = transform.ErrShortDst
184 break
185 }
186 dst[nDst+0] = uint8(r >> 8)
187 dst[nDst+1] = uint8(r)
188 nDst += 2
189 continue
190 }
191 return nDst, nSrc, err
192 }
193
194 func init() {
195 // Check that the hard-coded encode switch covers all tables.
196 if numEncodeTables != 8 {
197 panic("bad numEncodeTables")
198 }
199 }
200