/usr/share/gocode/src/golang.org/x/text/encoding/unicode/utf32/utf32.go is in golang-golang-x-text-dev 0.0~git20170627.0.6353ef0-1ubuntu2.
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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 | // Copyright 2016 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 utf32 provides the UTF-32 Unicode encoding.
//
// Please note that support for UTF-32 is discouraged as it is a rare and
// inefficient encoding, unfit for use as an interchange format. For use
// on the web, the W3C strongly discourages its use
// (https://www.w3.org/TR/html5/document-metadata.html#charset)
// while WHATWG directly prohibits supporting it
// (https://html.spec.whatwg.org/multipage/syntax.html#character-encodings).
package utf32 // import "golang.org/x/text/encoding/unicode/utf32"
import (
"errors"
"unicode/utf8"
"golang.org/x/text/encoding"
"golang.org/x/text/encoding/internal/identifier"
"golang.org/x/text/transform"
)
// All lists a configuration for each IANA-defined UTF-32 variant.
var All = []encoding.Encoding{
UTF32(BigEndian, UseBOM),
UTF32(BigEndian, IgnoreBOM),
UTF32(LittleEndian, IgnoreBOM),
}
// ErrMissingBOM means that decoding UTF-32 input with ExpectBOM did not
// find a starting byte order mark.
var ErrMissingBOM = errors.New("encoding: missing byte order mark")
// UTF32 returns a UTF-32 Encoding for the given default endianness and
// byte order mark (BOM) policy.
//
// When decoding from UTF-32 to UTF-8, if the BOMPolicy is IgnoreBOM then
// neither BOMs U+FEFF nor ill-formed code units 0xFFFE0000 in the input
// stream will affect the endianness used for decoding. Instead BOMs will
// be output as their standard UTF-8 encoding "\xef\xbb\xbf" while
// 0xFFFE0000 code units will be output as "\xef\xbf\xbd", the standard
// UTF-8 encoding for the Unicode replacement character. If the BOMPolicy
// is UseBOM or ExpectBOM a starting BOM is not written to the UTF-8
// output. Instead, it overrides the default endianness e for the remainder
// of the transformation. Any subsequent BOMs U+FEFF or ill-formed code
// units 0xFFFE0000 will not affect the endianness used, and will instead
// be output as their standard UTF-8 (replacement) encodings. For UseBOM,
// if there is no starting BOM, it will proceed with the default
// Endianness. For ExpectBOM, in that case, the transformation will return
// early with an ErrMissingBOM error.
//
// When encoding from UTF-8 to UTF-32, a BOM will be inserted at the start
// of the output if the BOMPolicy is UseBOM or ExpectBOM. Otherwise, a BOM
// will not be inserted. The UTF-8 input does not need to contain a BOM.
//
// There is no concept of a 'native' endianness. If the UTF-32 data is
// produced and consumed in a greater context that implies a certain
// endianness, use IgnoreBOM. Otherwise, use ExpectBOM and always produce
// and consume a BOM.
//
// In the language of http://www.unicode.org/faq/utf_bom.html#bom10,
// IgnoreBOM corresponds to "Where the precise type of the data stream is
// known... the BOM should not be used" and ExpectBOM corresponds to "A
// particular protocol... may require use of the BOM".
func UTF32(e Endianness, b BOMPolicy) encoding.Encoding {
return utf32Encoding{config{e, b}, mibValue[e][b&bomMask]}
}
// mibValue maps Endianness and BOMPolicy settings to MIB constants for UTF-32.
// Note that some configurations map to the same MIB identifier.
var mibValue = map[Endianness][numBOMValues]identifier.MIB{
BigEndian: [numBOMValues]identifier.MIB{
IgnoreBOM: identifier.UTF32BE,
UseBOM: identifier.UTF32,
},
LittleEndian: [numBOMValues]identifier.MIB{
IgnoreBOM: identifier.UTF32LE,
UseBOM: identifier.UTF32,
},
// ExpectBOM is not widely used and has no valid MIB identifier.
}
// BOMPolicy is a UTF-32 encodings's byte order mark policy.
type BOMPolicy uint8
const (
writeBOM BOMPolicy = 0x01
acceptBOM BOMPolicy = 0x02
requireBOM BOMPolicy = 0x04
bomMask BOMPolicy = 0x07
// HACK: numBOMValues == 8 triggers a bug in the 1.4 compiler (cannot have a
// map of an array of length 8 of a type that is also used as a key or value
// in another map). See golang.org/issue/11354.
// TODO: consider changing this value back to 8 if the use of 1.4.* has
// been minimized.
numBOMValues = 8 + 1
// IgnoreBOM means to ignore any byte order marks.
IgnoreBOM BOMPolicy = 0
// Unicode-compliant interpretation for UTF-32BE/LE.
// UseBOM means that the UTF-32 form may start with a byte order mark,
// which will be used to override the default encoding.
UseBOM BOMPolicy = writeBOM | acceptBOM
// Unicode-compliant interpretation for UTF-32.
// ExpectBOM means that the UTF-32 form must start with a byte order mark,
// which will be used to override the default encoding.
ExpectBOM BOMPolicy = writeBOM | acceptBOM | requireBOM
// Consistent with BOMPolicy definition in golang.org/x/text/encoding/unicode
)
// Endianness is a UTF-32 encoding's default endianness.
type Endianness bool
const (
// BigEndian is UTF-32BE.
BigEndian Endianness = false
// LittleEndian is UTF-32LE.
LittleEndian Endianness = true
)
type config struct {
endianness Endianness
bomPolicy BOMPolicy
}
type utf32Encoding struct {
config
mib identifier.MIB
}
func (u utf32Encoding) NewDecoder() *encoding.Decoder {
return &encoding.Decoder{Transformer: &utf32Decoder{
initial: u.config,
current: u.config,
}}
}
func (u utf32Encoding) NewEncoder() *encoding.Encoder {
return &encoding.Encoder{Transformer: &utf32Encoder{
endianness: u.endianness,
initialBOMPolicy: u.bomPolicy,
currentBOMPolicy: u.bomPolicy,
}}
}
func (u utf32Encoding) ID() (mib identifier.MIB, other string) {
return u.mib, ""
}
func (u utf32Encoding) String() string {
e, b := "B", ""
if u.endianness == LittleEndian {
e = "L"
}
switch u.bomPolicy {
case ExpectBOM:
b = "Expect"
case UseBOM:
b = "Use"
case IgnoreBOM:
b = "Ignore"
}
return "UTF-32" + e + "E (" + b + " BOM)"
}
type utf32Decoder struct {
initial config
current config
}
func (u *utf32Decoder) Reset() {
u.current = u.initial
}
func (u *utf32Decoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
if len(src) == 0 {
if atEOF && u.current.bomPolicy&requireBOM != 0 {
return 0, 0, ErrMissingBOM
}
return 0, 0, nil
}
if u.current.bomPolicy&acceptBOM != 0 {
if len(src) < 4 {
return 0, 0, transform.ErrShortSrc
}
switch {
case src[0] == 0x00 && src[1] == 0x00 && src[2] == 0xfe && src[3] == 0xff:
u.current.endianness = BigEndian
nSrc = 4
case src[0] == 0xff && src[1] == 0xfe && src[2] == 0x00 && src[3] == 0x00:
u.current.endianness = LittleEndian
nSrc = 4
default:
if u.current.bomPolicy&requireBOM != 0 {
return 0, 0, ErrMissingBOM
}
}
u.current.bomPolicy = IgnoreBOM
}
var r rune
var dSize, sSize int
for nSrc < len(src) {
if nSrc+3 < len(src) {
x := uint32(src[nSrc+0])<<24 | uint32(src[nSrc+1])<<16 |
uint32(src[nSrc+2])<<8 | uint32(src[nSrc+3])
if u.current.endianness == LittleEndian {
x = x>>24 | (x >> 8 & 0x0000FF00) | (x << 8 & 0x00FF0000) | x<<24
}
r, sSize = rune(x), 4
if dSize = utf8.RuneLen(r); dSize < 0 {
r, dSize = utf8.RuneError, 3
}
} else if atEOF {
// 1..3 trailing bytes.
r, dSize, sSize = utf8.RuneError, 3, len(src)-nSrc
} else {
err = transform.ErrShortSrc
break
}
if nDst+dSize > len(dst) {
err = transform.ErrShortDst
break
}
nDst += utf8.EncodeRune(dst[nDst:], r)
nSrc += sSize
}
return nDst, nSrc, err
}
type utf32Encoder struct {
endianness Endianness
initialBOMPolicy BOMPolicy
currentBOMPolicy BOMPolicy
}
func (u *utf32Encoder) Reset() {
u.currentBOMPolicy = u.initialBOMPolicy
}
func (u *utf32Encoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
if u.currentBOMPolicy&writeBOM != 0 {
if len(dst) < 4 {
return 0, 0, transform.ErrShortDst
}
dst[0], dst[1], dst[2], dst[3] = 0x00, 0x00, 0xfe, 0xff
u.currentBOMPolicy = IgnoreBOM
nDst = 4
}
r, size := rune(0), 0
for nSrc < len(src) {
r = rune(src[nSrc])
// Decode a 1-byte rune.
if r < utf8.RuneSelf {
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
break
}
}
}
if nDst+4 > len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst+0] = uint8(r >> 24)
dst[nDst+1] = uint8(r >> 16)
dst[nDst+2] = uint8(r >> 8)
dst[nDst+3] = uint8(r)
nDst += 4
nSrc += size
}
if u.endianness == LittleEndian {
for i := 0; i < nDst; i += 4 {
dst[i], dst[i+1], dst[i+2], dst[i+3] = dst[i+3], dst[i+2], dst[i+1], dst[i]
}
}
return nDst, nSrc, err
}
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