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| 1 // Copyright (c) 2011, 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 #library("json"); | |
| 6 | |
| 7 // Pure Dart implementation of JSON protocol. | |
| 8 | |
| 9 /** | |
| 10 * Utility class to parse JSON and serialize objects to JSON. | |
| 11 */ | |
| 12 class JSON { | |
| 13 /** | |
| 14 * Parses [:json:] and build the corresponding object. | |
| 15 */ | |
| 16 static parse(String json) { | |
| 17 return JsonParser.parse(json); | |
| 18 } | |
| 19 | |
| 20 /** | |
| 21 * Serializes [:object:] into JSON string. | |
| 22 */ | |
| 23 static String stringify(Object object) { | |
| 24 return JsonStringifier.stringify(object); | |
| 25 } | |
| 26 } | |
| 27 | |
| 28 //// Implementation /////////////////////////////////////////////////////////// | |
| 29 | |
| 30 /** | |
| 31 * Union-like class for JSON tokens. | |
| 32 */ | |
| 33 class JsonToken { | |
| 34 static final int STRING = 0; | |
| 35 static final int NUMBER = 1; | |
| 36 static final int NULL = 2; | |
| 37 static final int FALSE = 3; | |
| 38 static final int TRUE = 4; | |
| 39 static final int RBRACKET = 5; | |
| 40 static final int LBRACKET = 6; | |
| 41 static final int RBRACE = 7; | |
| 42 static final int LBRACE = 8; | |
| 43 static final int COLON = 9; | |
| 44 static final int COMMA = 10; | |
| 45 | |
| 46 final int kind; | |
| 47 final String _s; | |
| 48 final num _n; | |
| 49 | |
| 50 String get str() { | |
| 51 assert(kind == STRING); | |
| 52 return _s; | |
| 53 } | |
| 54 | |
| 55 num get number() { | |
| 56 assert(kind == NUMBER); | |
| 57 return _n; | |
| 58 } | |
| 59 | |
| 60 const JsonToken._internal(this.kind, this._s, this._n); | |
| 61 | |
| 62 factory JsonToken.string(String s) { | |
| 63 return new JsonToken._internal(STRING, s, 0); | |
| 64 } | |
| 65 factory JsonToken.number(num n) { | |
| 66 return new JsonToken._internal(NUMBER, '', n); | |
| 67 } | |
| 68 factory JsonToken.atom(int kind) { | |
| 69 return new JsonToken._internal(kind, '', 0); | |
| 70 } | |
| 71 | |
| 72 String toString() { | |
| 73 switch (kind) { | |
| 74 case STRING: | |
| 75 return 'STRING(${str})'; | |
| 76 | |
| 77 case NUMBER: | |
| 78 return 'NUMBER(${number})'; | |
| 79 | |
| 80 case NULL: | |
| 81 return 'ATOM(null)'; | |
| 82 | |
| 83 case FALSE: | |
| 84 return 'ATOM(false)'; | |
| 85 | |
| 86 case TRUE: | |
| 87 return 'ATOM(true)'; | |
| 88 | |
| 89 case RBRACKET: | |
| 90 return 'ATOM(])'; | |
| 91 | |
| 92 case LBRACKET: | |
| 93 return 'ATOM([)'; | |
| 94 | |
| 95 case RBRACE: | |
| 96 return 'ATOM(})'; | |
| 97 | |
| 98 case LBRACE: | |
| 99 return 'ATOM({)'; | |
| 100 | |
| 101 case COLON: | |
| 102 return 'ATOM(:)'; | |
| 103 | |
| 104 case COMMA: | |
| 105 return 'ATOM(,)'; | |
| 106 } | |
| 107 } | |
| 108 } | |
| 109 | |
| 110 typedef bool Predicate(int c); | |
| 111 | |
| 112 class JsonTokenizer { | |
| 113 static final int BACKSPACE = 8; // '\b'.charCodeAt(0) | |
| 114 static final int TAB = 9; // '\t'.charCodeAt(0) | |
| 115 static final int NEW_LINE = 10; // '\n'.charCodeAt(0) | |
| 116 static final int FORM_FEED = 12; // '\f'.charCodeAt(0) | |
| 117 static final int LINE_FEED = 13; // '\r'.charCodeAt(0) | |
| 118 static final int SPACE = 32; // ' '.charCodeAt(0) | |
| 119 static final int QUOTE = 34; // '"'.charCodeAt(0) | |
| 120 static final int PLUS = 43; // '+'.charCodeAt(0) | |
| 121 static final int COMMA = 44; // ','.charCodeAt(0) | |
| 122 static final int MINUS = 45; // '-'.charCodeAt(0) | |
| 123 static final int DOT = 46; // '.'.charCodeAt(0) | |
| 124 static final int SLASH = 47; // '/'.charCodeAt(0) | |
| 125 static final int ZERO = 48; // '0'.charCodeAt(0) | |
| 126 static final int NINE = 57; // '9'.charCodeAt(0) | |
| 127 static final int COLON = 58; // ':'.charCodeAt(0) | |
| 128 static final int A_BIG = 65; // 'A'.charCodeAt(0) | |
| 129 static final int E_BIG = 69; // 'E'.charCodeAt(0) | |
| 130 static final int Z_BIG = 90; // 'Z'.charCodeAt(0) | |
| 131 static final int LBRACKET = 91; // '['.charCodeAt(0) | |
| 132 static final int BACKSLASH = 92; // '\\'.charCodeAt(0) | |
| 133 static final int RBRACKET = 93; // ']'.charCodeAt(0) | |
| 134 static final int A_SMALL = 97; // 'a'.charCodeAt(0) | |
| 135 static final int B_SMALL = 98; // 'b'.charCodeAt(0) | |
| 136 static final int E_SMALL = 101; // 'e'.charCodeAt(0) | |
| 137 static final int N_SMALL = 110; // 'n'.charCodeAt(0) | |
| 138 static final int R_SMALL = 114; // 'r'.charCodeAt(0) | |
| 139 static final int Z_SMALL = 122; // 'z'.charCodeAt(0) | |
| 140 static final int LBRACE = 123; // '{'.charCodeAt(0) | |
| 141 static final int RBRACE = 125; // '}'.charCodeAt(0) | |
| 142 | |
| 143 JsonTokenizer(String s) : _s = s + ' ', _pos = 0, _len = s.length + 1 {} | |
| 144 | |
| 145 /** | |
| 146 * Fetches next token or [:null:] if the stream has been exhausted. | |
| 147 */ | |
| 148 JsonToken next() { | |
| 149 while (_pos < _len && isWhitespace(_s.charCodeAt(_pos))) { | |
| 150 _pos++; | |
| 151 } | |
| 152 if (_pos == _len) { | |
| 153 return null; | |
| 154 } | |
| 155 | |
| 156 final int cur = _s.charCodeAt(_pos); | |
| 157 switch (true) { | |
| 158 case cur == QUOTE: | |
| 159 _pos++; | |
| 160 List<int> charCodes = new List<int>(); | |
| 161 while (_pos < _len) { | |
| 162 int c = _s.charCodeAt(_pos); | |
| 163 if (c == QUOTE) { | |
| 164 break; | |
| 165 } | |
| 166 if (c == BACKSLASH) { | |
| 167 _pos++; | |
| 168 if (_pos == _len) { | |
| 169 throw '\\ at the end'; | |
| 170 } | |
| 171 | |
| 172 switch (_s[_pos]) { | |
| 173 case '"': | |
| 174 c = QUOTE; | |
| 175 break; | |
| 176 case '\\': | |
| 177 c = BACKSLASH; | |
| 178 break; | |
| 179 case '/': | |
| 180 c = SLASH; | |
| 181 break; | |
| 182 case 'b': | |
| 183 c = BACKSPACE; | |
| 184 break; | |
| 185 case 'n': | |
| 186 c = NEW_LINE; | |
| 187 break; | |
| 188 case 'r': | |
| 189 c = LINE_FEED; | |
| 190 break; | |
| 191 case 'f': | |
| 192 c = FORM_FEED; | |
| 193 break; | |
| 194 case 't': | |
| 195 c = TAB; | |
| 196 break; | |
| 197 case 'u': | |
| 198 if (_pos + 5 > _len) { | |
| 199 throw 'Invalid unicode esacape sequence: \\' + | |
| 200 _s.substring(_pos, _len); | |
| 201 } | |
| 202 final codeString = _s.substring(_pos + 1, _pos + 5); | |
| 203 c = Math.parseInt('0x' + codeString); | |
| 204 if (c >= 128) { | |
| 205 // TODO(jmessery): the VM doesn't support 2-byte strings yet | |
| 206 // see runtime/lib/string.cc:49 | |
| 207 // So instead we replace these characters with '?' | |
| 208 c = '?'.charCodeAt(0); | |
| 209 } | |
| 210 _pos += 4; | |
| 211 break; | |
| 212 default: | |
| 213 throw 'Invalid esacape sequence: \\' + _s[_pos]; | |
| 214 } | |
| 215 } | |
| 216 charCodes.add(c); | |
| 217 _pos++; | |
| 218 } | |
| 219 if (_pos == _len) { | |
| 220 throw 'Unmatched quote'; | |
| 221 } | |
| 222 | |
| 223 final String body = new String.fromCharCodes(charCodes); | |
| 224 _pos++; | |
| 225 return new JsonToken.string(body); | |
| 226 | |
| 227 case cur == MINUS || isDigit(cur): | |
| 228 skipDigits() { | |
| 229 _scanWhile((int c) => isDigit(c), 'Invalid number'); | |
| 230 } | |
| 231 | |
| 232 int c = cur; | |
| 233 final int startPos = _pos; | |
| 234 int value = 0; | |
| 235 bool isNegative = false; | |
| 236 if (c == MINUS) { | |
| 237 isNegative = true; | |
| 238 _pos++; | |
| 239 c = _s.charCodeAt(_pos); | |
| 240 } | |
| 241 while (isDigit(c)) { | |
| 242 value = value * 10 + c - ZERO; | |
| 243 _pos++; | |
| 244 c = _s.charCodeAt(_pos); | |
| 245 } | |
| 246 | |
| 247 if (c != DOT) { | |
| 248 if (c != E_SMALL && cur != E_BIG) { | |
| 249 if (isNegative) value = -value; | |
| 250 return new JsonToken.number(value); | |
| 251 } | |
| 252 } else { | |
| 253 _pos++; | |
| 254 skipDigits(); | |
| 255 c = _s.charCodeAt(_pos); | |
| 256 } | |
| 257 | |
| 258 if (c == E_SMALL || c == E_BIG) { | |
| 259 // TODO: consider keeping E+ as an integer. | |
| 260 _pos++; | |
| 261 c = _s.charCodeAt(_pos); | |
| 262 if (c == PLUS || c == MINUS) { | |
| 263 _pos++; | |
| 264 } | |
| 265 skipDigits(); | |
| 266 } | |
| 267 | |
| 268 final String body = _s.substring(startPos, _pos); | |
| 269 return new JsonToken.number(Math.parseDouble(body)); | |
| 270 | |
| 271 case cur == LBRACE: | |
| 272 _pos++; | |
| 273 return new JsonToken.atom(JsonToken.LBRACE); | |
| 274 | |
| 275 case cur == RBRACE: | |
| 276 _pos++; | |
| 277 return new JsonToken.atom(JsonToken.RBRACE); | |
| 278 | |
| 279 case cur == LBRACKET: | |
| 280 _pos++; | |
| 281 return new JsonToken.atom(JsonToken.LBRACKET); | |
| 282 | |
| 283 case cur == RBRACKET: | |
| 284 _pos++; | |
| 285 return new JsonToken.atom(JsonToken.RBRACKET); | |
| 286 | |
| 287 case cur == COMMA: | |
| 288 _pos++; | |
| 289 return new JsonToken.atom(JsonToken.COMMA); | |
| 290 | |
| 291 case cur == COLON: | |
| 292 _pos++; | |
| 293 return new JsonToken.atom(JsonToken.COLON); | |
| 294 | |
| 295 case isLetter(cur): | |
| 296 final int startPos = _pos; | |
| 297 _pos++; | |
| 298 while (_pos < _len && isLetter(_s.charCodeAt(_pos))) { | |
| 299 _pos++; | |
| 300 } | |
| 301 final String body = _s.substring(startPos, _pos); | |
| 302 switch (body) { | |
| 303 case 'null': | |
| 304 return new JsonToken.atom(JsonToken.NULL); | |
| 305 | |
| 306 case 'false': | |
| 307 return new JsonToken.atom(JsonToken.FALSE); | |
| 308 | |
| 309 case 'true': | |
| 310 return new JsonToken.atom(JsonToken.TRUE); | |
| 311 | |
| 312 default: | |
| 313 throw 'Unexpected sequence ${body}'; | |
| 314 } | |
| 315 // TODO: Bogous, to please DartVM. | |
| 316 return null; | |
| 317 | |
| 318 default: | |
| 319 throw 'Invalid token'; | |
| 320 } | |
| 321 } | |
| 322 | |
| 323 final String _s; | |
| 324 int _pos; | |
| 325 final int _len; | |
| 326 | |
| 327 void _scanWhile(Predicate predicate, String errorMsg) { | |
| 328 while (_pos < _len && predicate(_s.charCodeAt(_pos))) { | |
| 329 _pos++; | |
| 330 } | |
| 331 if (_pos == _len) { | |
| 332 throw errorMsg; | |
| 333 } | |
| 334 } | |
| 335 | |
| 336 // TODO other kind of whitespace. | |
| 337 static bool isWhitespace(int c) { | |
| 338 return c == SPACE || c == TAB || c == NEW_LINE || c == LINE_FEED; | |
| 339 } | |
| 340 static bool isDigit(int c) { | |
| 341 return (ZERO <= c) && (c <= NINE); | |
| 342 } | |
| 343 static bool isLetter(int c) { | |
| 344 return ((A_SMALL <= c) && (c <= Z_SMALL)) || ((A_BIG <= c) && (c <= Z_BIG))
; | |
| 345 } | |
| 346 } | |
| 347 | |
| 348 class JsonParser { | |
| 349 static parse(String json) { | |
| 350 return new JsonParser._internal(json)._parseToplevel(); | |
| 351 } | |
| 352 | |
| 353 final JsonTokenizer _tokenizer; | |
| 354 | |
| 355 JsonParser._internal(String json) : _tokenizer = new JsonTokenizer(json) {} | |
| 356 | |
| 357 _parseToplevel() { | |
| 358 JsonToken token = _tokenizer.next(); | |
| 359 final result = _parseValue(token); | |
| 360 token = _tokenizer.next(); | |
| 361 if (token !== null) { | |
| 362 throw 'Junk at the end'; | |
| 363 } | |
| 364 return result; | |
| 365 } | |
| 366 | |
| 367 _parseValue(final JsonToken token) { | |
| 368 if (token === null) { | |
| 369 throw 'Nothing to parse'; | |
| 370 } | |
| 371 switch (token.kind) { | |
| 372 case JsonToken.STRING: | |
| 373 return token.str; | |
| 374 | |
| 375 case JsonToken.NUMBER: | |
| 376 return token.number; | |
| 377 | |
| 378 case JsonToken.NULL: | |
| 379 return null; | |
| 380 | |
| 381 case JsonToken.FALSE: | |
| 382 return false; | |
| 383 | |
| 384 case JsonToken.TRUE: | |
| 385 return true; | |
| 386 | |
| 387 case JsonToken.LBRACE: | |
| 388 return _parseObject(); | |
| 389 | |
| 390 case JsonToken.LBRACKET: | |
| 391 return _parseList(); | |
| 392 | |
| 393 default: | |
| 394 throw 'Unexpected token: ${token}'; | |
| 395 } | |
| 396 } | |
| 397 | |
| 398 _parseObject() { | |
| 399 Map<String, Object> object = new Map<String, Object>(); | |
| 400 | |
| 401 _parseSequence(JsonToken.RBRACE, (JsonToken token) { | |
| 402 _assertTokenKind(token, JsonToken.STRING); | |
| 403 final String key = token.str; | |
| 404 | |
| 405 token = _tokenizer.next(); | |
| 406 _assertTokenKind(token, JsonToken.COLON); | |
| 407 | |
| 408 token = _tokenizer.next(); | |
| 409 final value = _parseValue(token); | |
| 410 | |
| 411 object[key] = value; | |
| 412 }); | |
| 413 | |
| 414 return object; | |
| 415 } | |
| 416 | |
| 417 _parseList() { | |
| 418 List<Object> list = new List<Object>(); | |
| 419 | |
| 420 _parseSequence(JsonToken.RBRACKET, (JsonToken token) { | |
| 421 final value = _parseValue(token); | |
| 422 list.add(value); | |
| 423 }); | |
| 424 | |
| 425 return list; | |
| 426 } | |
| 427 | |
| 428 void _parseSequence(int endTokenKind, void parseElement(JsonToken token)) { | |
| 429 JsonToken token = _tokenizer.next(); | |
| 430 if (token === null) { | |
| 431 throw 'Unexpected end of stream'; | |
| 432 } | |
| 433 if (token.kind == endTokenKind) { | |
| 434 return; | |
| 435 } | |
| 436 | |
| 437 parseElement(token); | |
| 438 | |
| 439 token = _tokenizer.next(); | |
| 440 if (token === null) { | |
| 441 throw 'Expected either comma or terminator'; | |
| 442 } | |
| 443 while (token.kind != endTokenKind) { | |
| 444 _assertTokenKind(token, JsonToken.COMMA); | |
| 445 | |
| 446 token = _tokenizer.next(); | |
| 447 parseElement(token); | |
| 448 | |
| 449 token = _tokenizer.next(); | |
| 450 } | |
| 451 } | |
| 452 | |
| 453 void _assertTokenKind(JsonToken token, int kind) { | |
| 454 if (token === null || token.kind != kind) { | |
| 455 throw 'Unexpected token kind: token = ${token}, expected kind = ${kind}'; | |
| 456 } | |
| 457 } | |
| 458 | |
| 459 // TODO: consider factor out error throwing code and build more complicated | |
| 460 // data structure to provide more info for a caller. | |
| 461 } | |
| 462 | |
| 463 // TODO: proper base class. | |
| 464 class JsonUnsupportedObjectType { | |
| 465 const JsonUnsupportedObjectType(); | |
| 466 } | |
| 467 | |
| 468 class JsonStringifier { | |
| 469 static String stringify(final object) { | |
| 470 JsonStringifier stringifier = new JsonStringifier._internal(); | |
| 471 stringifier._stringify(object); | |
| 472 return stringifier._result; | |
| 473 } | |
| 474 | |
| 475 JsonStringifier._internal() | |
| 476 : _sb = new StringBuffer(), _seen = new List<Object>() {} | |
| 477 StringBuffer _sb; | |
| 478 List<Object> _seen; // TODO: that should be identity set. | |
| 479 String get _result() { return _sb.toString(); } | |
| 480 | |
| 481 static String _numberToString(num x) { | |
| 482 // TODO: need some more investigation what to do with precision | |
| 483 // of double values. | |
| 484 switch (true) { | |
| 485 case x is int: | |
| 486 return x.toString(); | |
| 487 | |
| 488 case x is double: | |
| 489 return x.toString(); | |
| 490 | |
| 491 default: | |
| 492 return x.toDouble().toString(); | |
| 493 } | |
| 494 } | |
| 495 | |
| 496 // TODO: add others. | |
| 497 static bool _needsEscape(int charCode) { | |
| 498 return JsonTokenizer.QUOTE == charCode || JsonTokenizer.BACKSLASH == charCod
e | |
| 499 || JsonTokenizer.NEW_LINE == charCode || JsonTokenizer.LINE_FEED == charCo
de; | |
| 500 } | |
| 501 | |
| 502 static void _escape(StringBuffer sb, String s) { | |
| 503 // TODO: support \u code points. | |
| 504 // TODO: use writeCodePoint when implemented. | |
| 505 // TODO: use for each if implemented. | |
| 506 final int length = s.length; | |
| 507 bool needsEscape = false; | |
| 508 final charCodes = new List<int>(); | |
| 509 for (int i = 0; i < length; i++) { | |
| 510 int charCode = s.charCodeAt(i); | |
| 511 if (_needsEscape(charCode)) { | |
| 512 charCodes.add(JsonTokenizer.BACKSLASH); | |
| 513 needsEscape = true; | |
| 514 | |
| 515 if (JsonTokenizer.NEW_LINE == charCode) { | |
| 516 charCode = JsonTokenizer.N_SMALL; | |
| 517 } else if (JsonTokenizer.LINE_FEED == charCode) { | |
| 518 charCode = JsonTokenizer.R_SMALL; | |
| 519 } | |
| 520 } | |
| 521 charCodes.add(charCode); | |
| 522 } | |
| 523 sb.add(needsEscape ? new String.fromCharCodes(charCodes) : s); | |
| 524 } | |
| 525 | |
| 526 void _checkCycle(final object) { | |
| 527 // TODO: use Iterables. | |
| 528 for (int i = 0; i < _seen.length; i++) { | |
| 529 if (_seen[i] === object) { | |
| 530 throw 'Cyclic structure'; | |
| 531 } | |
| 532 } | |
| 533 _seen.add(object); | |
| 534 } | |
| 535 | |
| 536 void _stringify(final object) { | |
| 537 switch (true) { | |
| 538 case object is num: | |
| 539 // TODO: use writeOn. | |
| 540 _sb.add(_numberToString(object)); | |
| 541 return; | |
| 542 | |
| 543 case object === true: | |
| 544 _sb.add('true'); | |
| 545 return; | |
| 546 | |
| 547 case object === false: | |
| 548 _sb.add('false'); | |
| 549 return; | |
| 550 | |
| 551 case object === null: | |
| 552 _sb.add('null'); | |
| 553 return; | |
| 554 | |
| 555 case object is String: | |
| 556 _sb.add('"'); | |
| 557 _escape(_sb, object); | |
| 558 _sb.add('"'); | |
| 559 return; | |
| 560 | |
| 561 case object is List: | |
| 562 _checkCycle(object); | |
| 563 List a = object; | |
| 564 _sb.add('['); | |
| 565 if (a.length > 0) { | |
| 566 _stringify(a[0]); | |
| 567 // TODO: switch to Iterables. | |
| 568 for (int i = 1; i < a.length; i++) { | |
| 569 _sb.add(','); | |
| 570 _stringify(a[i]); | |
| 571 } | |
| 572 } | |
| 573 _sb.add(']'); | |
| 574 _seen.removeLast(); | |
| 575 return; | |
| 576 | |
| 577 case object is Map: | |
| 578 _checkCycle(object); | |
| 579 Map<String, Object> m = object; | |
| 580 _sb.add('{'); | |
| 581 bool first = true; | |
| 582 m.forEach((String key, Object value) { | |
| 583 if (!first) { | |
| 584 _sb.add(',"'); | |
| 585 } else { | |
| 586 _sb.add('"'); | |
| 587 } | |
| 588 _escape(_sb, key); | |
| 589 _sb.add('":'); | |
| 590 _stringify(value); | |
| 591 first = false; | |
| 592 }); | |
| 593 _sb.add('}'); | |
| 594 _seen.removeLast(); | |
| 595 return; | |
| 596 | |
| 597 default: | |
| 598 throw const JsonUnsupportedObjectType(); | |
| 599 } | |
| 600 } | |
| 601 } | |
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Chromium Code Reviews
Issue 9374030:
Move json to lib/json/{json.dart, json_frog.dart} (Closed)
Base URL: http://dart.googlecode.com/svn/branches/bleeding_edge/dart/