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| 1 // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 part of dart.convert; | |
| 6 | |
| 7 /** | |
| 8 * A [base64](https://tools.ietf.org/html/rfc4648) encoder and decoder. | |
| 9 * | |
| 10 * It encodes using the default base64 alphabet, | |
| 11 * decodes using both the base64 and base64url alphabets, | |
| 12 * does not allow invalid characters and requires padding. | |
| 13 * | |
| 14 * Examples: | |
| 15 * | |
| 16 * var encoded = BASE64.encode([0x62, 0x6c, 0xc3, 0xa5, 0x62, 0xc3, 0xa6, | |
| 17 * 0x72, 0x67, 0x72, 0xc3, 0xb8, 0x64]); | |
| 18 * var decoded = BASE64.decode("YmzDpWLDpnJncsO4ZAo="); | |
| 19 */ | |
| 20 const Base64Codec BASE64 = const Base64Codec(); | |
| 21 | |
| 22 /** | |
| 23 * A [base64url](https://tools.ietf.org/html/rfc4648) encoder and decoder. | |
| 24 * | |
| 25 * It encodes and decodes using the base64url alphabet, | |
| 26 * decodes using both the base64 and base64url alphabets, | |
| 27 * does not allow invalid characters and requires padding. | |
| 28 * | |
| 29 * Examples: | |
| 30 * | |
| 31 * var encoded = BASE64URL.encode([0x62, 0x6c, 0xc3, 0xa5, 0x62, 0xc3, 0xa6, | |
| 32 * 0x72, 0x67, 0x72, 0xc3, 0xb8, 0x64]); | |
| 33 * var decoded = BASE64URL.decode("YmzDpWLDpnJncsO4ZAo="); | |
| 34 */ | |
| 35 const Base64Codec BASE64URL = const Base64Codec.urlSafe(); | |
| 36 | |
| 37 // Constants used in more than one class. | |
| 38 const int _paddingChar = 0x3d; // '='. | |
| 39 | |
| 40 /** | |
| 41 * A [base64](https://tools.ietf.org/html/rfc4648) encoder and decoder. | |
| 42 * | |
| 43 * A [Base64Codec] allows base64 encoding bytes into ASCII strings and | |
| 44 * decoding valid encodings back to bytes. | |
| 45 * | |
| 46 * This implementation only handles the simplest RFC 4648 base64 and base64url | |
| 47 * encodings. | |
| 48 * It does not allow invalid characters when decoding and it requires, | |
| 49 * and generates, padding so that the input is always a multiple of four | |
| 50 * characters. | |
| 51 */ | |
| 52 class Base64Codec extends Codec<List<int>, String> { | |
| 53 final Base64Encoder _encoder; | |
| 54 const Base64Codec() : _encoder = const Base64Encoder(); | |
| 55 const Base64Codec.urlSafe() : _encoder = const Base64Encoder.urlSafe(); | |
| 56 | |
| 57 Base64Encoder get encoder => _encoder; | |
| 58 | |
| 59 Base64Decoder get decoder => const Base64Decoder(); | |
| 60 } | |
| 61 | |
| 62 // ------------------------------------------------------------------------ | |
| 63 // Encoder | |
| 64 // ------------------------------------------------------------------------ | |
| 65 | |
| 66 /** | |
| 67 * Base64 and base64url encoding converter. | |
| 68 * | |
| 69 * Encodes lists of bytes using base64 or base64url encoding. | |
| 70 * | |
| 71 * The results are ASCII strings using a restricted alphabet. | |
| 72 */ | |
| 73 class Base64Encoder extends Converter<List<int>, String> { | |
| 74 final bool _urlSafe; | |
| 75 | |
| 76 const Base64Encoder() : _urlSafe = false; | |
| 77 const Base64Encoder.urlSafe() : _urlSafe = true; | |
| 78 | |
| 79 String convert(List<int> input) { | |
| 80 if (input.isEmpty) return ""; | |
| 81 var encoder = new _Base64Encoder(_urlSafe); | |
| 82 Uint8List buffer = encoder.encode(input, 0, input.length, true); | |
| 83 return new String.fromCharCodes(buffer); | |
| 84 } | |
| 85 | |
| 86 ByteConversionSink startChunkedConversion(Sink<String> sink) { | |
| 87 if (sink is StringConversionSink) { | |
| 88 return new _Utf8Base64EncoderSink(sink.asUtf8Sink(false), _urlSafe); | |
| 89 } | |
| 90 return new _AsciiBase64EncoderSink(sink, _urlSafe); | |
| 91 } | |
| 92 } | |
| 93 | |
| 94 /** | |
| 95 * Helper class for encoding bytes to base64. | |
| 96 */ | |
| 97 class _Base64Encoder { | |
| 98 /** The RFC 4648 base64 encoding alphabet. */ | |
| 99 static const String _base64Alphabet = | |
| 100 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; | |
| 101 | |
| 102 /** The RFC 4648 base64url encoding alphabet. */ | |
| 103 static const String _base64urlAlphabet = | |
| 104 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"; | |
| 105 | |
| 106 /** Shift-count to extract the values stored in [_state]. */ | |
| 107 static const int _valueShift = 2; | |
| 108 | |
| 109 /** Mask to extract the count value stored in [_state]. */ | |
| 110 static const int _countMask = 3; | |
| 111 | |
| 112 static const int _sixBitMask = 0x3F; | |
| 113 | |
| 114 /** | |
| 115 * Intermediate state between chunks. | |
| 116 * | |
| 117 * Encoding handles three bytes at a time. | |
| 118 * If fewer than three bytes has been seen, this value encodes | |
| 119 * the number of bytes seen (0, 1 or 2) and their values. | |
| 120 */ | |
| 121 int _state = 0; | |
| 122 | |
| 123 /** Alphabet used for encoding. */ | |
| 124 final String _alphabet; | |
| 125 | |
| 126 _Base64Encoder(bool urlSafe) | |
| 127 : _alphabet = urlSafe ? _base64urlAlphabet : _base64Alphabet; | |
| 128 | |
| 129 /** Encode count and bits into a value to be stored in [_state]. */ | |
| 130 static int _encodeState(int count, int bits) { | |
| 131 assert(count <= _countMask); | |
| 132 return bits << _valueShift | count; | |
| 133 } | |
| 134 | |
| 135 /** Extract bits from encoded state. */ | |
| 136 static int _stateBits(int state) => state >> _valueShift; | |
| 137 | |
| 138 /** Extract count from encoded state. */ | |
| 139 static int _stateCount(int state) => state & _countMask; | |
| 140 | |
| 141 /** | |
| 142 * Create a [Uint8List] with the provided length. | |
| 143 */ | |
| 144 Uint8List createBuffer(int bufferLength) => new Uint8List(bufferLength); | |
| 145 | |
| 146 /** | |
| 147 * Encode [bytes] from [start] to [end] and the bits in [_state]. | |
| 148 * | |
| 149 * Returns a [Uint8List] of the ASCII codes of the encoded data. | |
| 150 * | |
| 151 * If the input, including left over [_state] from earlier encodings, | |
| 152 * are not a multiple of three bytes, then the partial state is stored | |
| 153 * back into [_state]. | |
| 154 * If [isLast] is true, partial state is encoded in the output instead, | |
| 155 * with the necessary padding. | |
| 156 * | |
| 157 * Returns `null` if there is no output. | |
| 158 */ | |
| 159 Uint8List encode(List<int> bytes, int start, int end, bool isLast) { | |
| 160 assert(0 <= start); | |
| 161 assert(start <= end); | |
| 162 assert(bytes == null || end <= bytes.length); | |
| 163 int length = end - start; | |
| 164 | |
| 165 int count = _stateCount(_state); | |
| 166 int byteCount = (count + length); | |
| 167 int fullChunks = byteCount ~/ 3; | |
| 168 int partialChunkLength = byteCount - fullChunks * 3; | |
| 169 int bufferLength = fullChunks * 4; | |
| 170 if (isLast && partialChunkLength > 0) { | |
| 171 bufferLength += 4; // Room for padding. | |
| 172 } | |
| 173 var output = createBuffer(bufferLength); | |
| 174 _state = encodeChunk(_alphabet, bytes, start, end, isLast, | |
| 175 output, 0, _state); | |
| 176 if (bufferLength > 0) return output; | |
| 177 // If the input plus the data in state is still less than three bytes, | |
| 178 // there may not be any output. | |
| 179 return null; | |
| 180 } | |
| 181 | |
| 182 static int encodeChunk(String alphabet, | |
| 183 List<int> bytes, int start, int end, bool isLast, | |
| 184 Uint8List output, int outputIndex, int state) { | |
| 185 int bits = _stateBits(state); | |
| 186 // Count number of missing bytes in three-byte chunk. | |
| 187 int expectedChars = 3 - _stateCount(state); | |
| 188 | |
| 189 // The input must be a list of bytes (integers in the range 0..255). | |
| 190 // The value of `byteOr` will be the bitwise or of all the values in | |
| 191 // `bytes` and a later check will validate that they were all valid bytes. | |
| 192 int byteOr = 0; | |
| 193 for (int i = start; i < end; i++) { | |
| 194 int byte = bytes[i]; | |
| 195 byteOr |= byte; | |
| 196 bits = ((bits << 8) | byte) & 0xFFFFFF; // Never store more than 24 bits. | |
| 197 expectedChars--; | |
| 198 if (expectedChars == 0) { | |
| 199 output[outputIndex++] = | |
| 200 alphabet.codeUnitAt((bits >> 18) & _sixBitMask); | |
| 201 output[outputIndex++] = | |
| 202 alphabet.codeUnitAt((bits >> 12) & _sixBitMask); | |
| 203 output[outputIndex++] = | |
| 204 alphabet.codeUnitAt((bits >> 6) & _sixBitMask); | |
| 205 output[outputIndex++] = | |
| 206 alphabet.codeUnitAt(bits & _sixBitMask); | |
| 207 expectedChars = 3; | |
| 208 bits = 0; | |
| 209 } | |
| 210 } | |
| 211 if (byteOr >= 0 && byteOr <= 255) { | |
| 212 if (isLast && expectedChars < 3) { | |
| 213 writeFinalChunk(alphabet, output, outputIndex, 3 - expectedChars, bits); | |
| 214 return 0; | |
| 215 } | |
| 216 return _encodeState(3 - expectedChars, bits); | |
| 217 } | |
| 218 | |
| 219 // There was an invalid byte value somewhere in the input - find it! | |
| 220 int i = start; | |
| 221 while (i < end) { | |
| 222 int byte = bytes[i]; | |
| 223 if (byte < 0 || byte > 255) break; | |
| 224 i++; | |
| 225 } | |
| 226 throw new ArgumentError.value(bytes, | |
| 227 "Not a byte value at index $i: 0x${bytes[i].toRadixString(16)}"); | |
| 228 } | |
| 229 | |
| 230 /** | |
| 231 * Writes a final encoded four-character chunk. | |
| 232 * | |
| 233 * Only used when the [_state] contains a partial (1 or 2 byte) | |
| 234 * input. | |
| 235 */ | |
| 236 static void writeFinalChunk(String alphabet, | |
| 237 Uint8List output, int outputIndex, | |
| 238 int count, int bits) { | |
| 239 assert(count > 0); | |
| 240 if (count == 1) { | |
| 241 output[outputIndex++] = | |
| 242 alphabet.codeUnitAt((bits >> 2) & _sixBitMask); | |
| 243 output[outputIndex++] = | |
| 244 alphabet.codeUnitAt((bits << 4) & _sixBitMask); | |
| 245 output[outputIndex++] = _paddingChar; | |
| 246 output[outputIndex++] = _paddingChar; | |
| 247 } else { | |
| 248 assert(count == 2); | |
| 249 output[outputIndex++] = | |
| 250 alphabet.codeUnitAt((bits >> 10) & _sixBitMask); | |
| 251 output[outputIndex++] = | |
| 252 alphabet.codeUnitAt((bits >> 4) & _sixBitMask); | |
| 253 output[outputIndex++] = | |
| 254 alphabet.codeUnitAt((bits << 2) & _sixBitMask); | |
| 255 output[outputIndex++] = _paddingChar; | |
| 256 } | |
| 257 } | |
| 258 } | |
| 259 | |
| 260 class _BufferCachingBase64Encoder extends _Base64Encoder { | |
| 261 /** | |
| 262 * Reused buffer. | |
| 263 * | |
| 264 * When the buffer isn't released to the sink, only used to create another | |
| 265 * value (a string), the buffer can be reused between chunks. | |
| 266 */ | |
| 267 Uint8List bufferCache; | |
| 268 | |
| 269 _BufferCachingBase64Encoder(bool urlSafe) : super(urlSafe); | |
| 270 | |
| 271 Uint8List createBuffer(int bufferLength) { | |
| 272 if (bufferCache == null || bufferCache.length < bufferLength) { | |
| 273 bufferCache = new Uint8List(bufferLength); | |
| 274 } | |
| 275 // Return a view of the buffer, so it has the reuested length. | |
| 276 return new Uint8List.view(bufferCache.buffer, 0, bufferLength); | |
| 277 } | |
| 278 } | |
| 279 | |
| 280 abstract class _Base64EncoderSink extends ByteConversionSinkBase { | |
| 281 void add(List<int> source) { | |
| 282 _add(source, 0, source.length, false); | |
| 283 } | |
| 284 | |
| 285 void close() { | |
| 286 _add(null, 0, 0, true); | |
| 287 } | |
| 288 | |
| 289 void addSlice(List<int> source, int start, int end, bool isLast) { | |
| 290 if (end == null) throw new ArgumentError.notNull("end"); | |
| 291 RangeError.checkValidRange(start, end, source.length); | |
| 292 _add(source, start, end, isLast); | |
| 293 } | |
| 294 | |
| 295 void _add(List<int> source, int start, int end, bool isLast); | |
| 296 } | |
| 297 | |
| 298 class _AsciiBase64EncoderSink extends _Base64EncoderSink { | |
| 299 final Sink<String> _sink; | |
| 300 final _Base64Encoder _encoder; | |
| 301 | |
| 302 _AsciiBase64EncoderSink(this._sink, bool urlSafe) | |
| 303 : _encoder = new _BufferCachingBase64Encoder(urlSafe); | |
| 304 | |
| 305 void _add(List<int> source, int start, int end, bool isLast) { | |
| 306 Uint8List buffer = _encoder.encode(source, start, end, isLast); | |
| 307 if (buffer != null) { | |
| 308 String string = new String.fromCharCodes(buffer); | |
| 309 _sink.add(string); | |
| 310 } | |
| 311 if (isLast) { | |
| 312 _sink.close(); | |
| 313 } | |
| 314 } | |
| 315 } | |
| 316 | |
| 317 class _Utf8Base64EncoderSink extends _Base64EncoderSink { | |
| 318 final ByteConversionSink _sink; | |
| 319 final _Base64Encoder _encoder; | |
| 320 | |
| 321 _Utf8Base64EncoderSink(this._sink, bool urlSafe) | |
| 322 : _encoder = new _Base64Encoder(urlSafe); | |
| 323 | |
| 324 void _add(List<int> source, int start, int end, bool isLast) { | |
| 325 Uint8List buffer = _encoder.encode(source, start, end, isLast); | |
| 326 if (buffer != null) { | |
| 327 _sink.addSlice(buffer, 0, buffer.length, isLast); | |
| 328 } | |
| 329 } | |
| 330 } | |
| 331 | |
| 332 // ------------------------------------------------------------------------ | |
| 333 // Decoder | |
| 334 // ------------------------------------------------------------------------ | |
| 335 | |
| 336 /** | |
| 337 * Decoder for base64 encoded data. | |
| 338 * | |
| 339 * This decoder accepts both base64 and base64url ("url-safe") encodings. | |
| 340 * | |
| 341 * The encoding is required to be properly padded. | |
| 342 */ | |
| 343 class Base64Decoder extends Converter<String, List<int>> { | |
| 344 | |
| 345 const Base64Decoder(); | |
| 346 | |
| 347 List<int> convert(String input, [int start = 0, int end]) { | |
| 348 end = RangeError.checkValidRange(start, end, input.length); | |
| 349 if (start == end) return new Uint8List(0); | |
| 350 var decoder = new _Base64Decoder(); | |
| 351 Uint8List buffer = decoder.decode(input, start, end); | |
| 352 decoder.close(input, end); | |
| 353 return buffer; | |
| 354 } | |
| 355 | |
| 356 StringConversionSink startChunkedConversion(Sink<List<int>> sink) { | |
| 357 return new _Base64DecoderSink(sink); | |
| 358 } | |
| 359 } | |
| 360 | |
| 361 /** | |
| 362 * Helper class implementing base64 decoding with intermediate state. | |
| 363 */ | |
| 364 class _Base64Decoder { | |
| 365 /** Shift-count to extract the values stored in [_state]. */ | |
| 366 static const int _valueShift = 2; | |
| 367 | |
| 368 /** Mask to extract the count value stored in [_state]. */ | |
| 369 static const int _countMask = 3; | |
| 370 | |
| 371 /** Invalid character in decoding table. */ | |
| 372 static const int _invalid = -2; | |
| 373 | |
| 374 /** Padding character in decoding table. */ | |
| 375 static const int _padding = -1; | |
| 376 | |
| 377 // Shorthands to make the table more readable. | |
| 378 static const int __ = _invalid; | |
| 379 static const int _p = _padding; | |
| 380 | |
| 381 /** | |
| 382 * Mapping from ASCII characters to their index in the base64 alphabet. | |
| 383 * | |
| 384 * Uses [_invalid] for invalid indices and [_padding] for the padding | |
| 385 * character. | |
| 386 * | |
| 387 * Accepts the "URL-safe" alphabet as well (`-` and `_` are the | |
| 388 * 62nd and 63rd alphabet characters), and considers `%` a padding | |
| 389 * character, which mush then be followed by `3D`, the percent-escape | |
| 390 * for `=`. | |
| 391 */ | |
| 392 static final List<int> _inverseAlphabet = new Int8List.fromList([ | |
| 393 __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, | |
| 394 __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, | |
| 395 __, __, __, __, __, _p, __, __, __, __, __, 62, __, 62, __, 63, | |
| 396 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, __, __, __, _p, __, __, | |
| 397 __, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, | |
| 398 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, __, __, __, __, 63, | |
| 399 __, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, | |
| 400 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, __, __, __, __, __, | |
| 401 ]); | |
| 402 | |
| 403 // Character constants. | |
| 404 static const int _char_percent = 0x25; // '%'. | |
| 405 static const int _char_3 = 0x33; // '3'. | |
| 406 static const int _char_d = 0x64; // 'd'. | |
| 407 | |
| 408 /** | |
| 409 * Maintains the intermediate state of a partly-decoded input. | |
| 410 * | |
| 411 * Base64 is decoded in chunks of four characters. If a chunk does not | |
| 412 * contain a full block, the decoded bits (six per character) of the | |
| 413 * available characters are stored in [_state] until the next call to | |
| 414 * [_decode] or [_close]. | |
| 415 * | |
| 416 * If no padding has been seen, the value is | |
| 417 * `numberOfCharactersSeen | (decodedBits << 2)` | |
| 418 * where `numberOfCharactersSeen` is between 0 and 3 and decoded bits | |
| 419 * contains six bits per seen character. | |
| 420 * | |
| 421 * If padding has been seen the value is negative. It's the bitwise negation | |
| 422 * of the number of remanining allowed padding characters (always ~0 or ~1). | |
| 423 * | |
| 424 * A state of `0` or `~0` are valid places to end decoding, all other values | |
| 425 * mean that a four-character block has not been completed. | |
| 426 */ | |
| 427 int _state = 0; | |
| 428 | |
| 429 /** | |
| 430 * Encodes [count] and [bits] as a value to be stored in [_state]. | |
| 431 */ | |
| 432 static int _encodeCharacterState(int count, int bits) { | |
| 433 assert(count == (count & _countMask)); | |
| 434 return (bits << _valueShift | count); | |
| 435 } | |
| 436 | |
| 437 /** | |
| 438 * Extracts count from a [_state] value. | |
| 439 */ | |
| 440 static int _stateCount(int state) { | |
| 441 assert(state >= 0); | |
| 442 return state & _countMask; | |
| 443 } | |
| 444 | |
| 445 /** | |
| 446 * Extracts value bits from a [_state] value. | |
| 447 */ | |
| 448 static int _stateBits(int state) { | |
| 449 assert(state >= 0); | |
| 450 return state >> _valueShift; | |
| 451 } | |
| 452 | |
| 453 /** | |
| 454 * Encodes a number of expected padding characters to be stored in [_state]. | |
| 455 */ | |
| 456 static int _encodePaddingState(int expectedPadding) { | |
| 457 assert(expectedPadding >= 0); | |
| 458 assert(expectedPadding <= 5); | |
| 459 return -expectedPadding - 1; // ~expectedPadding adapted to dart2js. | |
| 460 } | |
| 461 | |
| 462 /** | |
| 463 * Extracts expected padding character count from a [_state] value. | |
| 464 */ | |
| 465 static int _statePadding(int state) { | |
| 466 assert(state < 0); | |
| 467 return -state - 1; // ~state adapted to dart2js. | |
| 468 } | |
| 469 | |
| 470 static bool _hasSeenPadding(int state) => state < 0; | |
| 471 | |
| 472 /** | |
| 473 * Decodes [input] from [start] to [end]. | |
| 474 * | |
| 475 * Returns a [Uint8List] with the decoded bytes. | |
| 476 * If a previous call had an incomplete four-character block, the bits from | |
| 477 * those are included in decoding | |
| 478 */ | |
| 479 Uint8List decode(String input, int start, int end) { | |
| 480 assert(0 <= start); | |
| 481 assert(start <= end); | |
| 482 assert(end <= input.length); | |
| 483 if (_hasSeenPadding(_state)) { | |
| 484 _state = _checkPadding(input, start, end, _state); | |
| 485 return null; | |
| 486 } | |
| 487 if (start == end) return new Uint8List(0); | |
| 488 Uint8List buffer = _allocateBuffer(input, start, end, _state); | |
| 489 _state = decodeChunk(input, start, end, buffer, 0, _state); | |
| 490 return buffer; | |
| 491 } | |
| 492 | |
| 493 /** Checks that [_state] represents a valid decoding. */ | |
| 494 void close(String input, int end) { | |
| 495 if (_state < _encodePaddingState(0)) { | |
| 496 throw new FormatException("Missing padding character", input, end); | |
| 497 } | |
| 498 if (_state > 0) { | |
| 499 throw new FormatException("Invalid length, must be multiple of four", | |
| 500 input, end); | |
| 501 } | |
| 502 _state = _encodePaddingState(0); | |
| 503 } | |
| 504 | |
| 505 /** | |
| 506 * Decodes [input] from [start] to [end]. | |
| 507 * | |
| 508 * Includes the state returned by a previous call in the decoding. | |
| 509 * Writes the decoding to [output] at [outIndex], and there must | |
| 510 * be room in the output. | |
| 511 */ | |
| 512 static int decodeChunk(String input, int start, int end, | |
| 513 Uint8List output, int outIndex, | |
| 514 int state) { | |
| 515 assert(!_hasSeenPadding(state)); | |
| 516 const int asciiMask = 127; | |
| 517 const int asciiMax = 127; | |
| 518 const int eightBitMask = 0xFF; | |
| 519 const int bitsPerCharacter = 6; | |
| 520 | |
| 521 int bits = _stateBits(state); | |
| 522 int count = _stateCount(state); | |
| 523 // String contents should be all ASCII. | |
| 524 // Instead of checking for each character, we collect the bitwise-or of | |
| 525 // all the characters in `charOr` and later validate that all characters | |
| 526 // were ASCII. | |
| 527 int charOr = 0; | |
| 528 for (int i = start; i < end; i++) { | |
| 529 var char = input.codeUnitAt(i); | |
| 530 charOr |= char; | |
| 531 int code = _inverseAlphabet[char & asciiMask]; | |
| 532 if (code >= 0) { | |
| 533 bits = ((bits << bitsPerCharacter) | code) & 0xFFFFFF; | |
| 534 count = (count + 1) & 3; | |
| 535 if (count == 0) { | |
| 536 assert(outIndex + 3 <= output.length); | |
| 537 output[outIndex++] = (bits >> 16) & eightBitMask; | |
| 538 output[outIndex++] = (bits >> 8) & eightBitMask; | |
| 539 output[outIndex++] = bits & eightBitMask; | |
| 540 bits = 0; | |
| 541 } | |
| 542 continue; | |
| 543 } else if (code == _padding && count > 1) { | |
| 544 if (charOr < 0 || charOr > asciiMax) break; | |
| 545 if (count == 3) { | |
| 546 if ((bits & 0x03) != 0) { | |
| 547 throw new FormatException( | |
| 548 "Invalid encoding before padding", input, i); | |
| 549 } | |
| 550 output[outIndex++] = bits >> 10; | |
| 551 output[outIndex++] = bits >> 2; | |
| 552 } else { | |
| 553 if ((bits & 0x0F) != 0) { | |
| 554 throw new FormatException( | |
| 555 "Invalid encoding before padding", input, i); | |
| 556 } | |
| 557 output[outIndex++] = bits >> 4; | |
| 558 } | |
| 559 // Expected padding is the number of expected padding characters, | |
| 560 // where `=` counts as three and `%3D` counts as one per character. | |
| 561 // | |
| 562 // Expect either zero or one padding depending on count (2 or 3), | |
| 563 // plus two more characters if the code was `%` (a partial padding). | |
| 564 int expectedPadding = (3 - count) * 3; | |
| 565 if (char == _char_percent) expectedPadding += 2; | |
| 566 state = _encodePaddingState(expectedPadding); | |
| 567 return _checkPadding(input, i + 1, end, state); | |
| 568 } | |
| 569 throw new FormatException("Invalid character", input, i); | |
| 570 } | |
| 571 if (charOr >= 0 && charOr <= asciiMax) { | |
| 572 return _encodeCharacterState(count, bits); | |
| 573 } | |
| 574 // There is an invalid (non-ASCII) character in the input. | |
| 575 int i; | |
| 576 for (i = start; i < end; i++) { | |
| 577 int char = input.codeUnitAt(i); | |
| 578 if (char < 0 || char > asciiMax) break; | |
| 579 } | |
| 580 throw new FormatException("Invalid character", input, i); | |
| 581 } | |
| 582 | |
| 583 /** | |
| 584 * Allocates a buffer with room for the decoding of a substring of [input]. | |
| 585 * | |
| 586 * Includes room for the characters in [state], and handles padding correctly. | |
| 587 */ | |
| 588 static Uint8List _allocateBuffer(String input, int start, int end, | |
| 589 int state) { | |
| 590 assert(state >= 0); | |
| 591 int paddingStart = _trimPaddingChars(input, start, end); | |
| 592 int length = _stateCount(state) + (paddingStart - start); | |
| 593 // Three bytes per full four bytes in the input. | |
| 594 int bufferLength = (length >> 2) * 3; | |
| 595 // If padding was seen, then this is the last chunk, and the final partial | |
| 596 // chunk should be decoded too. | |
| 597 int remainderLength = length & 3; | |
| 598 if (remainderLength != 0 && paddingStart < end) { | |
| 599 bufferLength += remainderLength - 1; | |
| 600 } | |
| 601 if (bufferLength > 0) return new Uint8List(bufferLength); | |
| 602 // If the input plus state is less than four characters, and it's not | |
| 603 // at the end of input, no buffer is needed. | |
| 604 return null; | |
| 605 } | |
| 606 | |
| 607 /** | |
| 608 * Returns the position of the start of padding at the end of the input. | |
| 609 * | |
| 610 * Returns the end of input if there is no padding. | |
| 611 * | |
| 612 * This is used to ensure that the decoding buffer has the exact size | |
| 613 * it needs when input is valid, and at least enough bytes to reach the error | |
| 614 * when input is invalid. | |
| 615 * | |
| 616 * Never count more than two padding sequences since any more than that | |
| 617 * will raise an error anyway, and we only care about being precise for | |
| 618 * successful conversions. | |
| 619 */ | |
| 620 static int _trimPaddingChars(String input, int start, int end) { | |
| 621 // This may count '%=' as two paddings. That's ok, it will err later, | |
| 622 // but the buffer will be large enough to reach the error. | |
| 623 int padding = 0; | |
| 624 int index = end; | |
| 625 int newEnd = end; | |
| 626 while (index > start && padding < 2) { | |
| 627 index--; | |
| 628 int char = input.codeUnitAt(index); | |
| 629 if (char == _paddingChar) { | |
| 630 padding++; | |
| 631 newEnd = index; | |
| 632 continue; | |
| 633 } | |
| 634 if ((char | 0x20) == _char_d) { | |
| 635 if (index == start) break; | |
| 636 index--; | |
| 637 char = input.codeUnitAt(index); | |
| 638 } | |
| 639 if (char == _char_3) { | |
| 640 if (index == start) break; | |
| 641 index--; | |
| 642 char = input.codeUnitAt(index); | |
| 643 } | |
| 644 if (char == _char_percent) { | |
| 645 padding++; | |
| 646 newEnd = index; | |
| 647 continue; | |
| 648 } | |
| 649 break; | |
| 650 } | |
| 651 return newEnd; | |
| 652 } | |
| 653 | |
| 654 /** | |
| 655 * Check that the remainder of the string is valid padding. | |
| 656 * | |
| 657 * Valid padding is a correct number (0, 1 or 2) of `=` characters | |
| 658 * or `%3D` sequences depending on the number of preceding base64 characters. | |
| 659 * The [state] parameter encodes which padding continuations are allowed | |
| 660 * as the number of expected characters. That number is the number of | |
| 661 * expected padding characters times 3 minus the number of padding characters | |
| 662 * seen so far, where `=` counts as 3 counts as three characters, | |
| 663 * and the padding sequence `%3D` counts as one character per character. | |
| 664 * | |
| 665 * The number of missing characters is always between 0 and 5 because we | |
| 666 * only call this function after having seen at least one `=` or `%` | |
| 667 * character. | |
| 668 * If the number of missing characters is not 3 or 0, we have seen (at least) | |
| 669 * a `%` character and expects the rest of the `%3D` sequence, and a `=` is | |
| 670 * not allowed. When missing 3 characters, either `=` or `%` is allowed. | |
| 671 * | |
| 672 * When the value is 0, no more padding (or any other character) is allowed. | |
| 673 */ | |
| 674 static int _checkPadding(String input, int start, int end, int state) { | |
| 675 assert(_hasSeenPadding(state)); | |
| 676 if (start == end) return state; | |
| 677 int expectedPadding = _statePadding(state); | |
| 678 assert(expectedPadding >= 0); | |
| 679 assert(expectedPadding < 6); | |
| 680 while (expectedPadding > 0) { | |
| 681 int char = input.codeUnitAt(start); | |
| 682 if (expectedPadding == 3) { | |
| 683 if (char == _paddingChar) { | |
| 684 expectedPadding -= 3; | |
| 685 start++; | |
| 686 break; | |
| 687 } | |
| 688 if (char == _char_percent) { | |
| 689 expectedPadding--; | |
| 690 start++; | |
| 691 if (start == end) break; | |
| 692 char = input.codeUnitAt(start); | |
| 693 } else { | |
| 694 break; | |
| 695 } | |
| 696 } | |
| 697 // Partial padding means we have seen part of a "%3D" escape. | |
| 698 int expectedPartialPadding = expectedPadding; | |
| 699 if (expectedPartialPadding > 3) expectedPartialPadding -= 3; | |
| 700 if (expectedPartialPadding == 2) { | |
| 701 // Expects '3' | |
| 702 if (char != _char_3) break; | |
| 703 start++; | |
| 704 expectedPadding--; | |
| 705 if (start == end) break; | |
| 706 char = input.codeUnitAt(start); | |
| 707 } | |
| 708 // Expects 'D' or 'd'. | |
| 709 if ((char | 0x20) != _char_d) break; | |
| 710 start++; | |
| 711 expectedPadding--; | |
| 712 if (start == end) break; | |
| 713 } | |
| 714 if (start != end) { | |
| 715 throw new FormatException("Invalid padding character", | |
| 716 input, start); | |
| 717 } | |
| 718 return _encodePaddingState(expectedPadding); | |
| 719 } | |
| 720 } | |
| 721 | |
| 722 class _Base64DecoderSink extends StringConversionSinkBase { | |
| 723 /** Output sink */ | |
| 724 final Sink<List<int>> _sink; | |
| 725 final _Base64Decoder _decoder = new _Base64Decoder(); | |
| 726 | |
| 727 _Base64DecoderSink(this._sink); | |
| 728 | |
| 729 void add(String string) { | |
| 730 if (string.isEmpty) return; | |
| 731 Uint8List buffer = _decoder.decode(string, 0, string.length); | |
| 732 if (buffer != null) _sink.add(buffer); | |
| 733 } | |
| 734 | |
| 735 void close() { | |
| 736 _decoder.close(null, null); | |
| 737 _sink.close(); | |
| 738 } | |
| 739 | |
| 740 void addSlice(String string, int start, int end, bool isLast) { | |
| 741 end = RangeError.checkValidRange(start, end, string.length); | |
| 742 if (start == end) return; | |
| 743 Uint8List buffer = _decoder.decode(string, start, end); | |
| 744 if (buffer != null) _sink.add(buffer); | |
| 745 if (isLast) { | |
| 746 _decoder.close(string, end); | |
| 747 _sink.close(); | |
| 748 } | |
| 749 } | |
| 750 } | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2698353003:
unfork DDC's copy of most SDK libraries (Closed)
