summaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/text/encoding/charmap/charmap.go
blob: e89ff0734fdb43f7a85407855c883976c0cfa26a (plain)
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
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
// Copyright 2013 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.

//go:generate go run maketables.go

// Package charmap provides simple character encodings such as IBM Code Page 437
// and Windows 1252.
package charmap // import "golang.org/x/text/encoding/charmap"

import (
	"unicode/utf8"

	"golang.org/x/text/encoding"
	"golang.org/x/text/encoding/internal"
	"golang.org/x/text/encoding/internal/identifier"
	"golang.org/x/text/transform"
)

// These encodings vary only in the way clients should interpret them. Their
// coded character set is identical and a single implementation can be shared.
var (
	// ISO8859_6E is the ISO 8859-6E encoding.
	ISO8859_6E encoding.Encoding = &iso8859_6E

	// ISO8859_6I is the ISO 8859-6I encoding.
	ISO8859_6I encoding.Encoding = &iso8859_6I

	// ISO8859_8E is the ISO 8859-8E encoding.
	ISO8859_8E encoding.Encoding = &iso8859_8E

	// ISO8859_8I is the ISO 8859-8I encoding.
	ISO8859_8I encoding.Encoding = &iso8859_8I

	iso8859_6E = internal.Encoding{
		Encoding: ISO8859_6,
		Name:     "ISO-8859-6E",
		MIB:      identifier.ISO88596E,
	}

	iso8859_6I = internal.Encoding{
		Encoding: ISO8859_6,
		Name:     "ISO-8859-6I",
		MIB:      identifier.ISO88596I,
	}

	iso8859_8E = internal.Encoding{
		Encoding: ISO8859_8,
		Name:     "ISO-8859-8E",
		MIB:      identifier.ISO88598E,
	}

	iso8859_8I = internal.Encoding{
		Encoding: ISO8859_8,
		Name:     "ISO-8859-8I",
		MIB:      identifier.ISO88598I,
	}
)

// All is a list of all defined encodings in this package.
var All []encoding.Encoding = listAll

// TODO: implement these encodings, in order of importance.
// ASCII, ISO8859_1:       Rather common. Close to Windows 1252.
// ISO8859_9:              Close to Windows 1254.

// utf8Enc holds a rune's UTF-8 encoding in data[:len].
type utf8Enc struct {
	len  uint8
	data [3]byte
}

// Charmap is an 8-bit character set encoding.
type Charmap struct {
	// name is the encoding's name.
	name string
	// mib is the encoding type of this encoder.
	mib identifier.MIB
	// asciiSuperset states whether the encoding is a superset of ASCII.
	asciiSuperset bool
	// low is the lower bound of the encoded byte for a non-ASCII rune. If
	// Charmap.asciiSuperset is true then this will be 0x80, otherwise 0x00.
	low uint8
	// replacement is the encoded replacement character.
	replacement byte
	// decode is the map from encoded byte to UTF-8.
	decode [256]utf8Enc
	// encoding is the map from runes to encoded bytes. Each entry is a
	// uint32: the high 8 bits are the encoded byte and the low 24 bits are
	// the rune. The table entries are sorted by ascending rune.
	encode [256]uint32
}

// NewDecoder implements the encoding.Encoding interface.
func (m *Charmap) NewDecoder() *encoding.Decoder {
	return &encoding.Decoder{Transformer: charmapDecoder{charmap: m}}
}

// NewEncoder implements the encoding.Encoding interface.
func (m *Charmap) NewEncoder() *encoding.Encoder {
	return &encoding.Encoder{Transformer: charmapEncoder{charmap: m}}
}

// String returns the Charmap's name.
func (m *Charmap) String() string {
	return m.name
}

// ID implements an internal interface.
func (m *Charmap) ID() (mib identifier.MIB, other string) {
	return m.mib, ""
}

// charmapDecoder implements transform.Transformer by decoding to UTF-8.
type charmapDecoder struct {
	transform.NopResetter
	charmap *Charmap
}

func (m charmapDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
	for i, c := range src {
		if m.charmap.asciiSuperset && c < utf8.RuneSelf {
			if nDst >= len(dst) {
				err = transform.ErrShortDst
				break
			}
			dst[nDst] = c
			nDst++
			nSrc = i + 1
			continue
		}

		decode := &m.charmap.decode[c]
		n := int(decode.len)
		if nDst+n > len(dst) {
			err = transform.ErrShortDst
			break
		}
		// It's 15% faster to avoid calling copy for these tiny slices.
		for j := 0; j < n; j++ {
			dst[nDst] = decode.data[j]
			nDst++
		}
		nSrc = i + 1
	}
	return nDst, nSrc, err
}

// DecodeByte returns the Charmap's rune decoding of the byte b.
func (m *Charmap) DecodeByte(b byte) rune {
	switch x := &m.decode[b]; x.len {
	case 1:
		return rune(x.data[0])
	case 2:
		return rune(x.data[0]&0x1f)<<6 | rune(x.data[1]&0x3f)
	default:
		return rune(x.data[0]&0x0f)<<12 | rune(x.data[1]&0x3f)<<6 | rune(x.data[2]&0x3f)
	}
}

// charmapEncoder implements transform.Transformer by encoding from UTF-8.
type charmapEncoder struct {
	transform.NopResetter
	charmap *Charmap
}

func (m charmapEncoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
	r, size := rune(0), 0
loop:
	for nSrc < len(src) {
		if nDst >= len(dst) {
			err = transform.ErrShortDst
			break
		}
		r = rune(src[nSrc])

		// Decode a 1-byte rune.
		if r < utf8.RuneSelf {
			if m.charmap.asciiSuperset {
				nSrc++
				dst[nDst] = uint8(r)
				nDst++
				continue
			}
			size = 1

		} else {
			// Decode a multi-byte rune.
			r, size = utf8.DecodeRune(src[nSrc:])
			if size == 1 {
				// All valid runes of size 1 (those below utf8.RuneSelf) were
				// handled above. We have invalid UTF-8 or we haven't seen the
				// full character yet.
				if !atEOF && !utf8.FullRune(src[nSrc:]) {
					err = transform.ErrShortSrc
				} else {
					err = internal.RepertoireError(m.charmap.replacement)
				}
				break
			}
		}

		// Binary search in [low, high) for that rune in the m.charmap.encode table.
		for low, high := int(m.charmap.low), 0x100; ; {
			if low >= high {
				err = internal.RepertoireError(m.charmap.replacement)
				break loop
			}
			mid := (low + high) / 2
			got := m.charmap.encode[mid]
			gotRune := rune(got & (1<<24 - 1))
			if gotRune < r {
				low = mid + 1
			} else if gotRune > r {
				high = mid
			} else {
				dst[nDst] = byte(got >> 24)
				nDst++
				break
			}
		}
		nSrc += size
	}
	return nDst, nSrc, err
}

// EncodeRune returns the Charmap's byte encoding of the rune r. ok is whether
// r is in the Charmap's repertoire. If not, b is set to the Charmap's
// replacement byte. This is often the ASCII substitute character '\x1a'.
func (m *Charmap) EncodeRune(r rune) (b byte, ok bool) {
	if r < utf8.RuneSelf && m.asciiSuperset {
		return byte(r), true
	}
	for low, high := int(m.low), 0x100; ; {
		if low >= high {
			return m.replacement, false
		}
		mid := (low + high) / 2
		got := m.encode[mid]
		gotRune := rune(got & (1<<24 - 1))
		if gotRune < r {
			low = mid + 1
		} else if gotRune > r {
			high = mid
		} else {
			return byte(got >> 24), true
		}
	}
}