shiftjis.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 japanese
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 // ShiftJIS is the Shift JIS encoding, also known as Code Page 932 and
17 // Windows-31J.
18 var ShiftJIS encoding.Encoding = &shiftJIS
19
20 var shiftJIS = internal.Encoding{
21 Encoding: &internal.SimpleEncoding{Decoder: shiftJISDecoder{}, Encoder: shiftJISEncoder{}},
22 Name: "Shift JIS",
23 MIB: identifier.ShiftJIS,
24 }
25
26 type shiftJISDecoder struct{ transform.NopResetter }
27
28 func (shiftJISDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
29 r, size := rune(0), 0
30 loop:
31 for ; nSrc < len(src); nSrc += size {
32 switch c0 := src[nSrc]; {
33 case c0 < utf8.RuneSelf:
34 r, size = rune(c0), 1
35
36 case 0xa1 <= c0 && c0 < 0xe0:
37 r, size = rune(c0)+(0xff61-0xa1), 1
38
39 case (0x81 <= c0 && c0 < 0xa0) || (0xe0 <= c0 && c0 < 0xfd):
40 if c0 <= 0x9f {
41 c0 -= 0x70
42 } else {
43 c0 -= 0xb0
44 }
45 c0 = 2*c0 - 0x21
46
47 if nSrc+1 >= len(src) {
48 if !atEOF {
49 err = transform.ErrShortSrc
50 break loop
51 }
52 r, size = '\ufffd', 1
53 goto write
54 }
55 c1 := src[nSrc+1]
56 switch {
57 case c1 < 0x40:
58 r, size = '\ufffd', 1 // c1 is ASCII so output on next round
59 goto write
60 case c1 < 0x7f:
61 c0--
62 c1 -= 0x40
63 case c1 == 0x7f:
64 r, size = '\ufffd', 1 // c1 is ASCII so output on next round
65 goto write
66 case c1 < 0x9f:
67 c0--
68 c1 -= 0x41
69 case c1 < 0xfd:
70 c1 -= 0x9f
71 default:
72 r, size = '\ufffd', 2
73 goto write
74 }
75 r, size = '\ufffd', 2
76 if i := int(c0)*94 + int(c1); i < len(jis0208Decode) {
77 r = rune(jis0208Decode[i])
78 if r == 0 {
79 r = '\ufffd'
80 }
81 }
82
83 case c0 == 0x80:
84 r, size = 0x80, 1
85
86 default:
87 r, size = '\ufffd', 1
88 }
89 write:
90 if nDst+utf8.RuneLen(r) > len(dst) {
91 err = transform.ErrShortDst
92 break loop
93 }
94 nDst += utf8.EncodeRune(dst[nDst:], r)
95 }
96 return nDst, nSrc, err
97 }
98
99 type shiftJISEncoder struct{ transform.NopResetter }
100
101 func (shiftJISEncoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
102 r, size := rune(0), 0
103 loop:
104 for ; nSrc < len(src); nSrc += size {
105 r = rune(src[nSrc])
106
107 // Decode a 1-byte rune.
108 if r < utf8.RuneSelf {
109 size = 1
110
111 } else {
112 // Decode a multi-byte rune.
113 r, size = utf8.DecodeRune(src[nSrc:])
114 if size == 1 {
115 // All valid runes of size 1 (those below utf8.RuneSelf) were
116 // handled above. We have invalid UTF-8 or we haven't seen the
117 // full character yet.
118 if !atEOF && !utf8.FullRune(src[nSrc:]) {
119 err = transform.ErrShortSrc
120 break loop
121 }
122 }
123
124 // func init checks that the switch covers all tables.
125 switch {
126 case encode0Low <= r && r < encode0High:
127 if r = rune(encode0[r-encode0Low]); r>>tableShift == jis0208 {
128 goto write2
129 }
130 case encode1Low <= r && r < encode1High:
131 if r = rune(encode1[r-encode1Low]); r>>tableShift == jis0208 {
132 goto write2
133 }
134 case encode2Low <= r && r < encode2High:
135 if r = rune(encode2[r-encode2Low]); r>>tableShift == jis0208 {
136 goto write2
137 }
138 case encode3Low <= r && r < encode3High:
139 if r = rune(encode3[r-encode3Low]); r>>tableShift == jis0208 {
140 goto write2
141 }
142 case encode4Low <= r && r < encode4High:
143 if r = rune(encode4[r-encode4Low]); r>>tableShift == jis0208 {
144 goto write2
145 }
146 case encode5Low <= r && r < encode5High:
147 if 0xff61 <= r && r < 0xffa0 {
148 r -= 0xff61 - 0xa1
149 goto write1
150 }
151 if r = rune(encode5[r-encode5Low]); r>>tableShift == jis0208 {
152 goto write2
153 }
154 }
155 err = internal.ErrASCIIReplacement
156 break
157 }
158
159 write1:
160 if nDst >= len(dst) {
161 err = transform.ErrShortDst
162 break
163 }
164 dst[nDst] = uint8(r)
165 nDst++
166 continue
167
168 write2:
169 j1 := uint8(r>>codeShift) & codeMask
170 j2 := uint8(r) & codeMask
171 if nDst+2 > len(dst) {
172 err = transform.ErrShortDst
173 break loop
174 }
175 if j1 <= 61 {
176 dst[nDst+0] = 129 + j1/2
177 } else {
178 dst[nDst+0] = 193 + j1/2
179 }
180 if j1&1 == 0 {
181 dst[nDst+1] = j2 + j2/63 + 64
182 } else {
183 dst[nDst+1] = j2 + 159
184 }
185 nDst += 2
186 continue
187 }
188 return nDst, nSrc, err
189 }
190