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| 1 /// Decodes bytes using the correct name. See [decodeBytes]. | |
| 2 library char_encodings; | |
| 3 | |
| 4 import 'dart:collection'; | |
| 5 import 'package:utf/utf.dart'; | |
| 6 | |
| 7 // TODO(jmesserly): this function is conspicuously absent from dart:utf. | |
| 8 /// Returns true if the [bytes] starts with a UTF-8 byte order mark. | |
| 9 /// Since UTF-8 doesn't have byte order, it's somewhat of a misnomer, but it is | |
| 10 /// used in HTML to detect the UTF- | |
| 11 bool hasUtf8Bom(List<int> bytes, [int offset = 0, int length]) { | |
| 12 int end = length != null ? offset + length : bytes.length; | |
| 13 return (offset + 3) <= end && | |
| 14 bytes[offset] == 0xEF && | |
| 15 bytes[offset + 1] == 0xBB && | |
| 16 bytes[offset + 2] == 0xBF; | |
| 17 } | |
| 18 | |
| 19 // TODO(jmesserly): it's unfortunate that this has to be one-shot on the entire | |
| 20 // file, but dart:utf does not expose stream-based decoders yet. | |
| 21 /// Decodes the [bytes] with the provided [encoding] and returns an iterable for | |
| 22 /// the codepoints. Supports the major unicode encodings as well as ascii and | |
| 23 /// and windows-1252 encodings. | |
| 24 Iterable<int> decodeBytes(String encoding, List<int> bytes, [int offset = 0, | |
| 25 int length, | |
| 26 int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) { | |
| 27 if (length == null) length = bytes.length; | |
| 28 final replace = replacementCodepoint; | |
| 29 switch (encoding) { | |
| 30 case 'ascii': | |
| 31 bytes = bytes.sublist(offset, offset + length); | |
| 32 // TODO(jmesserly): this was taken from runtime/bin/string_stream.dart | |
| 33 for (int byte in bytes) { | |
| 34 if (byte > 127) { | |
| 35 // TODO(jmesserly): ideally this would be DecoderException, like the | |
| 36 // one thrown in runtime/bin/string_stream.dart, but we don't want to | |
| 37 // depend on dart:io. | |
| 38 throw new FormatException("Illegal ASCII character $byte"); | |
| 39 } | |
| 40 } | |
| 41 return bytes; | |
| 42 | |
| 43 case 'windows-1252': | |
| 44 case 'cp1252': | |
| 45 return decodeWindows1252AsIterable(bytes, offset, length, replace); | |
| 46 | |
| 47 case 'utf-8': | |
| 48 // NOTE: to match the behavior of the other decode functions, we eat the | |
| 49 // utf-8 BOM here. | |
| 50 if (hasUtf8Bom(bytes, offset, length)) { | |
| 51 offset += 3; | |
| 52 length -= 3; | |
| 53 } | |
| 54 return decodeUtf8AsIterable(bytes, offset, length, replace); | |
| 55 | |
| 56 case 'utf-16': | |
| 57 return decodeUtf16AsIterable(bytes, offset, length, replace); | |
| 58 case 'utf-16-be': | |
| 59 return decodeUtf16beAsIterable(bytes, offset, length, true, replace); | |
| 60 case 'utf-16-le': | |
| 61 return decodeUtf16leAsIterable(bytes, offset, length, true, replace); | |
| 62 | |
| 63 case 'utf-32': | |
| 64 return decodeUtf32AsIterable(bytes, offset, length, replace); | |
| 65 case 'utf-32-be': | |
| 66 return decodeUtf32beAsIterable(bytes, offset, length, true, replace); | |
| 67 case 'utf-32-le': | |
| 68 return decodeUtf32leAsIterable(bytes, offset, length, true, replace); | |
| 69 | |
| 70 default: | |
| 71 throw new ArgumentError('Encoding $encoding not supported'); | |
| 72 } | |
| 73 } | |
| 74 | |
| 75 // TODO(jmesserly): use dart:utf once http://dartbug.com/6476 is fixed. | |
| 76 /// Returns the code points for the [input]. This works like [String.charCodes] | |
| 77 /// but it decodes UTF-16 surrogate pairs. | |
| 78 List<int> toCodepoints(String input) { | |
| 79 var newCodes = <int>[]; | |
| 80 for (int i = 0; i < input.length; i++) { | |
| 81 var c = input.codeUnitAt(i); | |
| 82 if (0xD800 <= c && c <= 0xDBFF) { | |
| 83 int next = i + 1; | |
| 84 if (next < input.length) { | |
| 85 var d = input.codeUnitAt(next); | |
| 86 if (0xDC00 <= d && d <= 0xDFFF) { | |
| 87 c = 0x10000 + ((c - 0xD800) << 10) + (d - 0xDC00); | |
| 88 i = next; | |
| 89 } | |
| 90 } | |
| 91 } | |
| 92 newCodes.add(c); | |
| 93 } | |
| 94 return newCodes; | |
| 95 } | |
| 96 | |
| 97 /// Decodes [windows-1252](http://en.wikipedia.org/wiki/Windows-1252) bytes as | |
| 98 /// an iterable. Thus, the consumer can only convert as much of the input as | |
| 99 /// needed. Set the [replacementCharacter] to null to throw an [ArgumentError] | |
| 100 /// rather than replace the bad value. | |
| 101 IterableWindows1252Decoder decodeWindows1252AsIterable(List<int> bytes, | |
| 102 [int offset = 0, int length, | |
| 103 int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) { | |
| 104 return new IterableWindows1252Decoder( | |
| 105 bytes, offset, length, replacementCodepoint); | |
| 106 } | |
| 107 | |
| 108 /// Return type of [decodeWindows1252AsIterable] and variants. The Iterable type | |
| 109 /// provides an iterator on demand and the iterator will only translate bytes | |
| 110 /// as requested by the user of the iterator. (Note: results are not cached.) | |
| 111 class IterableWindows1252Decoder extends IterableBase<int> { | |
| 112 final List<int> bytes; | |
| 113 final int offset; | |
| 114 final int length; | |
| 115 final int replacementCodepoint; | |
| 116 | |
| 117 IterableWindows1252Decoder(List<int> this.bytes, [int this.offset = 0, | |
| 118 int this.length = null, | |
| 119 int this.replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]); | |
| 120 | |
| 121 Windows1252Decoder get iterator => | |
| 122 new Windows1252Decoder(bytes, offset, length, replacementCodepoint); | |
| 123 } | |
| 124 | |
| 125 /// Provides an iterator of Unicode codepoints from windows-1252 encoded bytes. | |
| 126 /// The parameters can set an offset into a list of bytes (as int), limit the | |
| 127 /// length of the values to be decoded, and override the default Unicode | |
| 128 /// replacement character. Set the replacementCharacter to null to throw an | |
| 129 /// ArgumentError rather than replace the bad value. The return value | |
| 130 /// from this method can be used as an Iterable (e.g. in a for-loop). | |
| 131 class Windows1252Decoder implements Iterator<int> { | |
| 132 final int replacementCodepoint; | |
| 133 final List<int> _bytes; | |
| 134 int _offset; | |
| 135 final int _length; | |
| 136 | |
| 137 Windows1252Decoder(List<int> bytes, [int offset = 0, int length, | |
| 138 this.replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) | |
| 139 : _bytes = bytes, | |
| 140 _offset = offset - 1, | |
| 141 _length = length == null ? bytes.length : length; | |
| 142 | |
| 143 bool get _inRange => _offset >= 0 && _offset < _length; | |
| 144 int get current => _inRange ? _mapChar(_bytes[_offset]) : null; | |
| 145 | |
| 146 bool moveNext() { | |
| 147 _offset++; | |
| 148 return _inRange; | |
| 149 } | |
| 150 | |
| 151 int _mapChar(int char) { | |
| 152 // TODO(jmesserly): this is duplicating entitiesWindows1252 and | |
| 153 // replacementCharacters from constants.dart | |
| 154 switch (char) { | |
| 155 case 0x80: | |
| 156 return 0x20AC; // EURO SIGN | |
| 157 case 0x82: | |
| 158 return 0x201A; // SINGLE LOW-9 QUOTATION MARK | |
| 159 case 0x83: | |
| 160 return 0x0192; // LATIN SMALL LETTER F WITH HOOK | |
| 161 case 0x84: | |
| 162 return 0x201E; // DOUBLE LOW-9 QUOTATION MARK | |
| 163 case 0x85: | |
| 164 return 0x2026; // HORIZONTAL ELLIPSIS | |
| 165 case 0x86: | |
| 166 return 0x2020; // DAGGER | |
| 167 case 0x87: | |
| 168 return 0x2021; // DOUBLE DAGGER | |
| 169 case 0x88: | |
| 170 return 0x02C6; // MODIFIER LETTER CIRCUMFLEX ACCENT | |
| 171 case 0x89: | |
| 172 return 0x2030; // PER MILLE SIGN | |
| 173 case 0x8A: | |
| 174 return 0x0160; // LATIN CAPITAL LETTER S WITH CARON | |
| 175 case 0x8B: | |
| 176 return 0x2039; // SINGLE LEFT-POINTING ANGLE QUOTATION MARK | |
| 177 case 0x8C: | |
| 178 return 0x0152; // LATIN CAPITAL LIGATURE OE | |
| 179 case 0x8E: | |
| 180 return 0x017D; // LATIN CAPITAL LETTER Z WITH CARON | |
| 181 case 0x91: | |
| 182 return 0x2018; // LEFT SINGLE QUOTATION MARK | |
| 183 case 0x92: | |
| 184 return 0x2019; // RIGHT SINGLE QUOTATION MARK | |
| 185 case 0x93: | |
| 186 return 0x201C; // LEFT DOUBLE QUOTATION MARK | |
| 187 case 0x94: | |
| 188 return 0x201D; // RIGHT DOUBLE QUOTATION MARK | |
| 189 case 0x95: | |
| 190 return 0x2022; // BULLET | |
| 191 case 0x96: | |
| 192 return 0x2013; // EN DASH | |
| 193 case 0x97: | |
| 194 return 0x2014; // EM DASH | |
| 195 case 0x98: | |
| 196 return 0x02DC; // SMALL TILDE | |
| 197 case 0x99: | |
| 198 return 0x2122; // TRADE MARK SIGN | |
| 199 case 0x9A: | |
| 200 return 0x0161; // LATIN SMALL LETTER S WITH CARON | |
| 201 case 0x9B: | |
| 202 return 0x203A; // SINGLE RIGHT-POINTING ANGLE QUOTATION MARK | |
| 203 case 0x9C: | |
| 204 return 0x0153; // LATIN SMALL LIGATURE OE | |
| 205 case 0x9E: | |
| 206 return 0x017E; // LATIN SMALL LETTER Z WITH CARON | |
| 207 case 0x9F: | |
| 208 return 0x0178; // LATIN CAPITAL LETTER Y WITH DIAERESIS | |
| 209 | |
| 210 case 0x81: | |
| 211 case 0x8D: | |
| 212 case 0x8F: | |
| 213 case 0x90: | |
| 214 case 0x9D: | |
| 215 if (replacementCodepoint == null) { | |
| 216 throw new ArgumentError( | |
| 217 "Invalid windows-1252 code point $char at $_offset"); | |
| 218 } | |
| 219 return replacementCodepoint; | |
| 220 } | |
| 221 return char; | |
| 222 } | |
| 223 } | |
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