runtime/JSONObject.cpp

   1 /*
   2  * Copyright (C) 2009 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "JSONObject.h"
  28
  29 #include "BooleanObject.h"
  30 #include "Error.h"
  31 #include "ExceptionHelpers.h"
  32 #include "JSArray.h"
  33 #include "JSGlobalObject.h"
  34 #include "LiteralParser.h"
  35 #include "Local.h"
  36 #include "LocalScope.h"
  37 #include "Lookup.h"
  38 #include "ObjectConstructor.h"
  39 #include "Operations.h"
  40 #include "PropertyNameArray.h"
  41 #include <wtf/MathExtras.h>
  42 #include <wtf/text/StringBuilder.h>
  43
  44 namespace JSC {
  45
  46 ASSERT_HAS_TRIVIAL_DESTRUCTOR(JSONObject);
  47
  48 static EncodedJSValue JSC_HOST_CALL JSONProtoFuncParse(ExecState*);
  49 static EncodedJSValue JSC_HOST_CALL JSONProtoFuncStringify(ExecState*);
  50
  51 }
  52
  53 #include "JSONObject.lut.h"
  54
  55 namespace JSC {
  56
  57 JSONObject::JSONObject(JSGlobalObject* globalObject, Structure* structure)
  58     : JSNonFinalObject(globalObject->vm(), structure)
  59 {
  60 }
  61
  62 void JSONObject::finishCreation(JSGlobalObject* globalObject)
  63 {
  64     Base::finishCreation(globalObject->vm());
  65     ASSERT(inherits(&s_info));
  66 }
  67
  68 // PropertyNameForFunctionCall objects must be on the stack, since the JSValue that they create is not marked.
  69 class PropertyNameForFunctionCall {
  70 public:
  71     PropertyNameForFunctionCall(const Identifier&);
  72     PropertyNameForFunctionCall(unsigned);
  73
  74     JSValue value(ExecState*) const;
  75
  76 private:
  77     const Identifier* m_identifier;
  78     unsigned m_number;
  79     mutable JSValue m_value;
  80 };
  81
  82 class Stringifier {
  83     WTF_MAKE_NONCOPYABLE(Stringifier);
  84 public:
  85     Stringifier(ExecState*, const Local<Unknown>& replacer, const Local<Unknown>& space);
  86     Local<Unknown> stringify(Handle<Unknown>);
  87
  88     void visitAggregate(SlotVisitor&);
  89
  90 private:
  91     class Holder {
  92     public:
  93         Holder(VM&, JSObject*);
  94
  95         JSObject* object() const { return m_object.get(); }
  96
  97         bool appendNextProperty(Stringifier&, StringBuilder&);
  98
  99     private:
 100         Local<JSObject> m_object;
 101         const bool m_isArray;
 102         bool m_isJSArray;
 103         unsigned m_index;
 104         unsigned m_size;
 105         RefPtr<PropertyNameArrayData> m_propertyNames;
 106     };
 107
 108     friend class Holder;
 109
 110     static void appendQuotedString(StringBuilder&, const String&);
 111
 112     JSValue toJSON(JSValue, const PropertyNameForFunctionCall&);
 113
 114     enum StringifyResult { StringifyFailed, StringifySucceeded, StringifyFailedDueToUndefinedValue };
 115     StringifyResult appendStringifiedValue(StringBuilder&, JSValue, JSObject* holder, const PropertyNameForFunctionCall&);
 116
 117     bool willIndent() const;
 118     void indent();
 119     void unindent();
 120     void startNewLine(StringBuilder&) const;
 121
 122     ExecState* const m_exec;
 123     const Local<Unknown> m_replacer;
 124     bool m_usingArrayReplacer;
 125     PropertyNameArray m_arrayReplacerPropertyNames;
 126     CallType m_replacerCallType;
 127     CallData m_replacerCallData;
 128     const String m_gap;
 129
 130     Vector<Holder, 16, UnsafeVectorOverflow> m_holderStack;
 131     String m_repeatedGap;
 132     String m_indent;
 133 };
 134
 135 // ------------------------------ helper functions --------------------------------
 136
 137 static inline JSValue unwrapBoxedPrimitive(ExecState* exec, JSValue value)
 138 {
 139     if (!value.isObject())
 140         return value;
 141     JSObject* object = asObject(value);
 142     if (object->inherits(&NumberObject::s_info))
 143         return jsNumber(object->toNumber(exec));
 144     if (object->inherits(&StringObject::s_info))
 145         return object->toString(exec);
 146     if (object->inherits(&BooleanObject::s_info))
 147         return object->toPrimitive(exec);
 148     return value;
 149 }
 150
 151 static inline String gap(ExecState* exec, JSValue space)
 152 {
 153     const unsigned maxGapLength = 10;
 154     space = unwrapBoxedPrimitive(exec, space);
 155
 156     // If the space value is a number, create a gap string with that number of spaces.
 157     if (space.isNumber()) {
 158         double spaceCount = space.asNumber();
 159         int count;
 160         if (spaceCount > maxGapLength)
 161             count = maxGapLength;
 162         else if (!(spaceCount > 0))
 163             count = 0;
 164         else
 165             count = static_cast<int>(spaceCount);
 166         UChar spaces[maxGapLength];
 167         for (int i = 0; i < count; ++i)
 168             spaces[i] = ' ';
 169         return String(spaces, count);
 170     }
 171
 172     // If the space value is a string, use it as the gap string, otherwise use no gap string.
 173     String spaces = space.getString(exec);
 174     if (spaces.length() > maxGapLength) {
 175         spaces = spaces.substringSharingImpl(0, maxGapLength);
 176     }
 177     return spaces;
 178 }
 179
 180 // ------------------------------ PropertyNameForFunctionCall --------------------------------
 181
 182 inline PropertyNameForFunctionCall::PropertyNameForFunctionCall(const Identifier& identifier)
 183     : m_identifier(&identifier)
 184 {
 185 }
 186
 187 inline PropertyNameForFunctionCall::PropertyNameForFunctionCall(unsigned number)
 188     : m_identifier(0)
 189     , m_number(number)
 190 {
 191 }
 192
 193 JSValue PropertyNameForFunctionCall::value(ExecState* exec) const
 194 {
 195     if (!m_value) {
 196         if (m_identifier)
 197             m_value = jsString(exec, m_identifier->string());
 198         else
 199             m_value = jsNumber(m_number);
 200     }
 201     return m_value;
 202 }
 203
 204 // ------------------------------ Stringifier --------------------------------
 205
 206 Stringifier::Stringifier(ExecState* exec, const Local<Unknown>& replacer, const Local<Unknown>& space)
 207     : m_exec(exec)
 208     , m_replacer(replacer)
 209     , m_usingArrayReplacer(false)
 210     , m_arrayReplacerPropertyNames(exec)
 211     , m_replacerCallType(CallTypeNone)
 212     , m_gap(gap(exec, space.get()))
 213 {
 214     if (!m_replacer.isObject())
 215         return;
 216
 217     if (m_replacer.asObject()->inherits(&JSArray::s_info)) {
 218         m_usingArrayReplacer = true;
 219         Handle<JSObject> array = m_replacer.asObject();
 220         unsigned length = array->get(exec, exec->vm().propertyNames->length).toUInt32(exec);
 221         for (unsigned i = 0; i < length; ++i) {
 222             JSValue name = array->get(exec, i);
 223             if (exec->hadException())
 224                 break;
 225
 226             if (name.isObject()) {
 227                 if (!asObject(name)->inherits(&NumberObject::s_info) && !asObject(name)->inherits(&StringObject::s_info))
 228                     continue;
 229             }
 230
 231             m_arrayReplacerPropertyNames.add(Identifier(exec, name.toString(exec)->value(exec)));
 232         }
 233         return;
 234     }
 235
 236     m_replacerCallType = m_replacer.asObject()->methodTable()->getCallData(m_replacer.asObject().get(), m_replacerCallData);
 237 }
 238
 239 Local<Unknown> Stringifier::stringify(Handle<Unknown> value)
 240 {
 241     JSObject* object = constructEmptyObject(m_exec);
 242     if (m_exec->hadException())
 243         return Local<Unknown>(m_exec->vm(), jsNull());
 244
 245     PropertyNameForFunctionCall emptyPropertyName(m_exec->vm().propertyNames->emptyIdentifier);
 246     object->putDirect(m_exec->vm(), m_exec->vm().propertyNames->emptyIdentifier, value.get());
 247
 248     StringBuilder result;
 249     if (appendStringifiedValue(result, value.get(), object, emptyPropertyName) != StringifySucceeded)
 250         return Local<Unknown>(m_exec->vm(), jsUndefined());
 251     if (m_exec->hadException())
 252         return Local<Unknown>(m_exec->vm(), jsNull());
 253
 254     return Local<Unknown>(m_exec->vm(), jsString(m_exec, result.toString()));
 255 }
 256
 257 template <typename CharType>
 258 static void appendStringToStringBuilder(StringBuilder& builder, const CharType* data, int length)
 259 {
 260     for (int i = 0; i < length; ++i) {
 261         int start = i;
 262         while (i < length && (data[i] > 0x1F && data[i] != '"' && data[i] != '\\'))
 263             ++i;
 264         builder.append(data + start, i - start);
 265         if (i >= length)
 266             break;
 267         switch (data[i]) {
 268         case '\t':
 269             builder.append('\\');
 270             builder.append('t');
 271             break;
 272         case '\r':
 273             builder.append('\\');
 274             builder.append('r');
 275             break;
 276         case '\n':
 277             builder.append('\\');
 278             builder.append('n');
 279             break;
 280         case '\f':
 281             builder.append('\\');
 282             builder.append('f');
 283             break;
 284         case '\b':
 285             builder.append('\\');
 286             builder.append('b');
 287             break;
 288         case '"':
 289             builder.append('\\');
 290             builder.append('"');
 291             break;
 292         case '\\':
 293             builder.append('\\');
 294             builder.append('\\');
 295             break;
 296         default:
 297             static const char hexDigits[] = "0123456789abcdef";
 298             UChar ch = data[i];
 299             LChar hex[] = { '\\', 'u', static_cast<LChar>(hexDigits[(ch >> 12) & 0xF]), static_cast<LChar>(hexDigits[(ch >> 8) & 0xF]), static_cast<LChar>(hexDigits[(ch >> 4) & 0xF]), static_cast<LChar>(hexDigits[ch & 0xF]) };
 300             builder.append(hex, WTF_ARRAY_LENGTH(hex));
 301             break;
 302         }
 303     }
 304 }
 305
 306 void Stringifier::appendQuotedString(StringBuilder& builder, const String& value)
 307 {
 308     int length = value.length();
 309
 310     builder.append('"');
 311
 312     if (value.is8Bit())
 313         appendStringToStringBuilder<LChar>(builder, value.characters8(), length);
 314     else
 315         appendStringToStringBuilder<UChar>(builder, value.characters16(), length);
 316
 317     builder.append('"');
 318 }
 319
 320 inline JSValue Stringifier::toJSON(JSValue value, const PropertyNameForFunctionCall& propertyName)
 321 {
 322     ASSERT(!m_exec->hadException());
 323     if (!value.isObject() || !asObject(value)->hasProperty(m_exec, m_exec->vm().propertyNames->toJSON))
 324         return value;
 325
 326     JSValue toJSONFunction = asObject(value)->get(m_exec, m_exec->vm().propertyNames->toJSON);
 327     if (m_exec->hadException())
 328         return jsNull();
 329
 330     if (!toJSONFunction.isObject())
 331         return value;
 332
 333     JSObject* object = asObject(toJSONFunction);
 334     CallData callData;
 335     CallType callType = object->methodTable()->getCallData(object, callData);
 336     if (callType == CallTypeNone)
 337         return value;
 338
 339     MarkedArgumentBuffer args;
 340     args.append(propertyName.value(m_exec));
 341     return call(m_exec, object, callType, callData, value, args);
 342 }
 343
 344 Stringifier::StringifyResult Stringifier::appendStringifiedValue(StringBuilder& builder, JSValue value, JSObject* holder, const PropertyNameForFunctionCall& propertyName)
 345 {
 346     // Call the toJSON function.
 347     value = toJSON(value, propertyName);
 348     if (m_exec->hadException())
 349         return StringifyFailed;
 350
 351     // Call the replacer function.
 352     if (m_replacerCallType != CallTypeNone) {
 353         MarkedArgumentBuffer args;
 354         args.append(propertyName.value(m_exec));
 355         args.append(value);
 356         value = call(m_exec, m_replacer.get(), m_replacerCallType, m_replacerCallData, holder, args);
 357         if (m_exec->hadException())
 358             return StringifyFailed;
 359     }
 360
 361     if (value.isUndefined() && !holder->inherits(&JSArray::s_info))
 362         return StringifyFailedDueToUndefinedValue;
 363
 364     if (value.isNull()) {
 365         builder.appendLiteral("null");
 366         return StringifySucceeded;
 367     }
 368
 369     value = unwrapBoxedPrimitive(m_exec, value);
 370
 371     if (m_exec->hadException())
 372         return StringifyFailed;
 373
 374     if (value.isBoolean()) {
 375         if (value.isTrue())
 376             builder.appendLiteral("true");
 377         else
 378             builder.appendLiteral("false");
 379         return StringifySucceeded;
 380     }
 381
 382     String stringValue;
 383     if (value.getString(m_exec, stringValue)) {
 384         appendQuotedString(builder, stringValue);
 385         return StringifySucceeded;
 386     }
 387
 388     if (value.isNumber()) {
 389         double number = value.asNumber();
 390         if (!std::isfinite(number))
 391             builder.appendLiteral("null");
 392         else
 393             builder.append(String::numberToStringECMAScript(number));
 394         return StringifySucceeded;
 395     }
 396
 397     if (!value.isObject())
 398         return StringifyFailed;
 399
 400     JSObject* object = asObject(value);
 401
 402     CallData callData;
 403     if (object->methodTable()->getCallData(object, callData) != CallTypeNone) {
 404         if (holder->inherits(&JSArray::s_info)) {
 405             builder.appendLiteral("null");
 406             return StringifySucceeded;
 407         }
 408         return StringifyFailedDueToUndefinedValue;
 409     }
 410
 411     // Handle cycle detection, and put the holder on the stack.
 412     for (unsigned i = 0; i < m_holderStack.size(); i++) {
 413         if (m_holderStack[i].object() == object) {
 414             throwError(m_exec, createTypeError(m_exec, ASCIILiteral("JSON.stringify cannot serialize cyclic structures.")));
 415             return StringifyFailed;
 416         }
 417     }
 418     bool holderStackWasEmpty = m_holderStack.isEmpty();
 419     m_holderStack.append(Holder(m_exec->vm(), object));
 420     if (!holderStackWasEmpty)
 421         return StringifySucceeded;
 422
 423     do {
 424         while (m_holderStack.last().appendNextProperty(*this, builder)) {
 425             if (m_exec->hadException())
 426                 return StringifyFailed;
 427         }
 428         m_holderStack.removeLast();
 429     } while (!m_holderStack.isEmpty());
 430     return StringifySucceeded;
 431 }
 432
 433 inline bool Stringifier::willIndent() const
 434 {
 435     return !m_gap.isEmpty();
 436 }
 437
 438 inline void Stringifier::indent()
 439 {
 440     // Use a single shared string, m_repeatedGap, so we don't keep allocating new ones as we indent and unindent.
 441     unsigned newSize = m_indent.length() + m_gap.length();
 442     if (newSize > m_repeatedGap.length())
 443         m_repeatedGap = makeString(m_repeatedGap, m_gap);
 444     ASSERT(newSize <= m_repeatedGap.length());
 445     m_indent = m_repeatedGap.substringSharingImpl(0, newSize);
 446 }
 447
 448 inline void Stringifier::unindent()
 449 {
 450     ASSERT(m_indent.length() >= m_gap.length());
 451     m_indent = m_repeatedGap.substringSharingImpl(0, m_indent.length() - m_gap.length());
 452 }
 453
 454 inline void Stringifier::startNewLine(StringBuilder& builder) const
 455 {
 456     if (m_gap.isEmpty())
 457         return;
 458     builder.append('\n');
 459     builder.append(m_indent);
 460 }
 461
 462 inline Stringifier::Holder::Holder(VM& vm, JSObject* object)
 463     : m_object(vm, object)
 464     , m_isArray(object->inherits(&JSArray::s_info))
 465     , m_index(0)
 466 #ifndef NDEBUG
 467     , m_size(0)
 468 #endif
 469 {
 470 }
 471
 472 bool Stringifier::Holder::appendNextProperty(Stringifier& stringifier, StringBuilder& builder)
 473 {
 474     ASSERT(m_index <= m_size);
 475
 476     ExecState* exec = stringifier.m_exec;
 477
 478     // First time through, initialize.
 479     if (!m_index) {
 480         if (m_isArray) {
 481             m_isJSArray = isJSArray(m_object.get());
 482             m_size = m_object->get(exec, exec->vm().propertyNames->length).toUInt32(exec);
 483             builder.append('[');
 484         } else {
 485             if (stringifier.m_usingArrayReplacer)
 486                 m_propertyNames = stringifier.m_arrayReplacerPropertyNames.data();
 487             else {
 488                 PropertyNameArray objectPropertyNames(exec);
 489                 m_object->methodTable()->getOwnPropertyNames(m_object.get(), exec, objectPropertyNames, ExcludeDontEnumProperties);
 490                 m_propertyNames = objectPropertyNames.releaseData();
 491             }
 492             m_size = m_propertyNames->propertyNameVector().size();
 493             builder.append('{');
 494         }
 495         stringifier.indent();
 496     }
 497
 498     // Last time through, finish up and return false.
 499     if (m_index == m_size) {
 500         stringifier.unindent();
 501         if (m_size && builder[builder.length() - 1] != '{')
 502             stringifier.startNewLine(builder);
 503         builder.append(m_isArray ? ']' : '}');
 504         return false;
 505     }
 506
 507     // Handle a single element of the array or object.
 508     unsigned index = m_index++;
 509     unsigned rollBackPoint = 0;
 510     StringifyResult stringifyResult;
 511     if (m_isArray) {
 512         // Get the value.
 513         JSValue value;
 514         if (m_isJSArray && asArray(m_object.get())->canGetIndexQuickly(index))
 515             value = asArray(m_object.get())->getIndexQuickly(index);
 516         else {
 517             PropertySlot slot(m_object.get());
 518             if (!m_object->methodTable()->getOwnPropertySlotByIndex(m_object.get(), exec, index, slot))
 519                 slot.setUndefined();
 520             if (exec->hadException())
 521                 return false;
 522             value = slot.getValue(exec, index);
 523         }
 524
 525         // Append the separator string.
 526         if (index)
 527             builder.append(',');
 528         stringifier.startNewLine(builder);
 529
 530         // Append the stringified value.
 531         stringifyResult = stringifier.appendStringifiedValue(builder, value, m_object.get(), index);
 532     } else {
 533         // Get the value.
 534         PropertySlot slot(m_object.get());
 535         Identifier& propertyName = m_propertyNames->propertyNameVector()[index];
 536         if (!m_object->methodTable()->getOwnPropertySlot(m_object.get(), exec, propertyName, slot))
 537             return true;
 538         JSValue value = slot.getValue(exec, propertyName);
 539         if (exec->hadException())
 540             return false;
 541
 542         rollBackPoint = builder.length();
 543
 544         // Append the separator string.
 545         if (builder[rollBackPoint - 1] != '{')
 546             builder.append(',');
 547         stringifier.startNewLine(builder);
 548
 549         // Append the property name.
 550         appendQuotedString(builder, propertyName.string());
 551         builder.append(':');
 552         if (stringifier.willIndent())
 553             builder.append(' ');
 554
 555         // Append the stringified value.
 556         stringifyResult = stringifier.appendStringifiedValue(builder, value, m_object.get(), propertyName);
 557     }
 558
 559     // From this point on, no access to the this pointer or to any members, because the
 560     // Holder object may have moved if the call to stringify pushed a new Holder onto
 561     // m_holderStack.
 562
 563     switch (stringifyResult) {
 564         case StringifyFailed:
 565             builder.appendLiteral("null");
 566             break;
 567         case StringifySucceeded:
 568             break;
 569         case StringifyFailedDueToUndefinedValue:
 570             // This only occurs when get an undefined value for an object property.
 571             // In this case we don't want the separator and property name that we
 572             // already appended, so roll back.
 573             builder.resize(rollBackPoint);
 574             break;
 575     }
 576
 577     return true;
 578 }
 579
 580 // ------------------------------ JSONObject --------------------------------
 581
 582 const ClassInfo JSONObject::s_info = { "JSON", &JSNonFinalObject::s_info, 0, ExecState::jsonTable, CREATE_METHOD_TABLE(JSONObject) };
 583
 584 /* Source for JSONObject.lut.h
 585 @begin jsonTable
 586   parse         JSONProtoFuncParse             DontEnum|Function 2
 587   stringify     JSONProtoFuncStringify         DontEnum|Function 3
 588 @end
 589 */
 590
 591 // ECMA 15.8
 592
 593 bool JSONObject::getOwnPropertySlot(JSCell* cell, ExecState* exec, PropertyName propertyName, PropertySlot& slot)
 594 {
 595     return getStaticFunctionSlot<JSObject>(exec, ExecState::jsonTable(exec), jsCast<JSONObject*>(cell), propertyName, slot);
 596 }
 597
 598 bool JSONObject::getOwnPropertyDescriptor(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)
 599 {
 600     return getStaticFunctionDescriptor<JSObject>(exec, ExecState::jsonTable(exec), jsCast<JSONObject*>(object), propertyName, descriptor);
 601 }
 602
 603 class Walker {
 604 public:
 605     Walker(ExecState* exec, Handle<JSObject> function, CallType callType, CallData callData)
 606         : m_exec(exec)
 607         , m_function(exec->vm(), function)
 608         , m_callType(callType)
 609         , m_callData(callData)
 610     {
 611     }
 612     JSValue walk(JSValue unfiltered);
 613 private:
 614     JSValue callReviver(JSObject* thisObj, JSValue property, JSValue unfiltered)
 615     {
 616         MarkedArgumentBuffer args;
 617         args.append(property);
 618         args.append(unfiltered);
 619         return call(m_exec, m_function.get(), m_callType, m_callData, thisObj, args);
 620     }
 621
 622     friend class Holder;
 623
 624     ExecState* m_exec;
 625     Local<JSObject> m_function;
 626     CallType m_callType;
 627     CallData m_callData;
 628 };
 629
 630 // We clamp recursion well beyond anything reasonable.
 631 static const unsigned maximumFilterRecursion = 40000;
 632 enum WalkerState { StateUnknown, ArrayStartState, ArrayStartVisitMember, ArrayEndVisitMember,
 633                                  ObjectStartState, ObjectStartVisitMember, ObjectEndVisitMember };
 634 NEVER_INLINE JSValue Walker::walk(JSValue unfiltered)
 635 {
 636     Vector<PropertyNameArray, 16, UnsafeVectorOverflow> propertyStack;
 637     Vector<uint32_t, 16, UnsafeVectorOverflow> indexStack;
 638     LocalStack<JSObject, 16> objectStack(m_exec->vm());
 639     LocalStack<JSArray, 16> arrayStack(m_exec->vm());
 640
 641     Vector<WalkerState, 16, UnsafeVectorOverflow> stateStack;
 642     WalkerState state = StateUnknown;
 643     JSValue inValue = unfiltered;
 644     JSValue outValue = jsNull();
 645
 646     while (1) {
 647         switch (state) {
 648             arrayStartState:
 649             case ArrayStartState: {
 650                 ASSERT(inValue.isObject());
 651                 ASSERT(isJSArray(asObject(inValue)) || asObject(inValue)->inherits(&JSArray::s_info));
 652                 if (objectStack.size() + arrayStack.size() > maximumFilterRecursion)
 653                     return throwError(m_exec, createStackOverflowError(m_exec));
 654
 655                 JSArray* array = asArray(inValue);
 656                 arrayStack.push(array);
 657                 indexStack.append(0);
 658                 // fallthrough
 659             }
 660             arrayStartVisitMember:
 661             case ArrayStartVisitMember: {
 662                 JSArray* array = arrayStack.peek();
 663                 uint32_t index = indexStack.last();
 664                 if (index == array->length()) {
 665                     outValue = array;
 666                     arrayStack.pop();
 667                     indexStack.removeLast();
 668                     break;
 669                 }
 670                 if (isJSArray(array) && array->canGetIndexQuickly(index))
 671                     inValue = array->getIndexQuickly(index);
 672                 else {
 673                     PropertySlot slot;
 674                     if (array->methodTable()->getOwnPropertySlotByIndex(array, m_exec, index, slot))
 675                         inValue = slot.getValue(m_exec, index);
 676                     else
 677                         inValue = jsUndefined();
 678                 }
 679
 680                 if (inValue.isObject()) {
 681                     stateStack.append(ArrayEndVisitMember);
 682                     goto stateUnknown;
 683                 } else
 684                     outValue = inValue;
 685                 // fallthrough
 686             }
 687             case ArrayEndVisitMember: {
 688                 JSArray* array = arrayStack.peek();
 689                 JSValue filteredValue = callReviver(array, jsString(m_exec, String::number(indexStack.last())), outValue);
 690                 if (filteredValue.isUndefined())
 691                     array->methodTable()->deletePropertyByIndex(array, m_exec, indexStack.last());
 692                 else
 693                     array->putDirectIndex(m_exec, indexStack.last(), filteredValue);
 694                 if (m_exec->hadException())
 695                     return jsNull();
 696                 indexStack.last()++;
 697                 goto arrayStartVisitMember;
 698             }
 699             objectStartState:
 700             case ObjectStartState: {
 701                 ASSERT(inValue.isObject());
 702                 ASSERT(!isJSArray(asObject(inValue)) && !asObject(inValue)->inherits(&JSArray::s_info));
 703                 if (objectStack.size() + arrayStack.size() > maximumFilterRecursion)
 704                     return throwError(m_exec, createStackOverflowError(m_exec));
 705
 706                 JSObject* object = asObject(inValue);
 707                 objectStack.push(object);
 708                 indexStack.append(0);
 709                 propertyStack.append(PropertyNameArray(m_exec));
 710                 object->methodTable()->getOwnPropertyNames(object, m_exec, propertyStack.last(), ExcludeDontEnumProperties);
 711                 // fallthrough
 712             }
 713             objectStartVisitMember:
 714             case ObjectStartVisitMember: {
 715                 JSObject* object = objectStack.peek();
 716                 uint32_t index = indexStack.last();
 717                 PropertyNameArray& properties = propertyStack.last();
 718                 if (index == properties.size()) {
 719                     outValue = object;
 720                     objectStack.pop();
 721                     indexStack.removeLast();
 722                     propertyStack.removeLast();
 723                     break;
 724                 }
 725                 PropertySlot slot;
 726                 if (object->methodTable()->getOwnPropertySlot(object, m_exec, properties[index], slot))
 727                     inValue = slot.getValue(m_exec, properties[index]);
 728                 else
 729                     inValue = jsUndefined();
 730
 731                 // The holder may be modified by the reviver function so any lookup may throw
 732                 if (m_exec->hadException())
 733                     return jsNull();
 734
 735                 if (inValue.isObject()) {
 736                     stateStack.append(ObjectEndVisitMember);
 737                     goto stateUnknown;
 738                 } else
 739                     outValue = inValue;
 740                 // fallthrough
 741             }
 742             case ObjectEndVisitMember: {
 743                 JSObject* object = objectStack.peek();
 744                 Identifier prop = propertyStack.last()[indexStack.last()];
 745                 PutPropertySlot slot;
 746                 JSValue filteredValue = callReviver(object, jsString(m_exec, prop.string()), outValue);
 747                 if (filteredValue.isUndefined())
 748                     object->methodTable()->deleteProperty(object, m_exec, prop);
 749                 else
 750                     object->methodTable()->put(object, m_exec, prop, filteredValue, slot);
 751                 if (m_exec->hadException())
 752                     return jsNull();
 753                 indexStack.last()++;
 754                 goto objectStartVisitMember;
 755             }
 756             stateUnknown:
 757             case StateUnknown:
 758                 if (!inValue.isObject()) {
 759                     outValue = inValue;
 760                     break;
 761                 }
 762                 JSObject* object = asObject(inValue);
 763                 if (isJSArray(object) || object->inherits(&JSArray::s_info))
 764                     goto arrayStartState;
 765                 goto objectStartState;
 766         }
 767         if (stateStack.isEmpty())
 768             break;
 769
 770         state = stateStack.last();
 771         stateStack.removeLast();
 772     }
 773     JSObject* finalHolder = constructEmptyObject(m_exec);
 774     PutPropertySlot slot;
 775     finalHolder->methodTable()->put(finalHolder, m_exec, m_exec->vm().propertyNames->emptyIdentifier, outValue, slot);
 776     return callReviver(finalHolder, jsEmptyString(m_exec), outValue);
 777 }
 778
 779 // ECMA-262 v5 15.12.2
 780 EncodedJSValue JSC_HOST_CALL JSONProtoFuncParse(ExecState* exec)
 781 {
 782     if (!exec->argumentCount())
 783         return throwVMError(exec, createError(exec, ASCIILiteral("JSON.parse requires at least one parameter")));
 784     String source = exec->argument(0).toString(exec)->value(exec);
 785     if (exec->hadException())
 786         return JSValue::encode(jsNull());
 787
 788     JSValue unfiltered;
 789     LocalScope scope(exec->vm());
 790     if (source.is8Bit()) {
 791         LiteralParser<LChar> jsonParser(exec, source.characters8(), source.length(), StrictJSON);
 792         unfiltered = jsonParser.tryLiteralParse();
 793         if (!unfiltered)
 794             return throwVMError(exec, createSyntaxError(exec, jsonParser.getErrorMessage()));
 795     } else {
 796         LiteralParser<UChar> jsonParser(exec, source.characters16(), source.length(), StrictJSON);
 797         unfiltered = jsonParser.tryLiteralParse();
 798         if (!unfiltered)
 799             return throwVMError(exec, createSyntaxError(exec, jsonParser.getErrorMessage()));
 800     }
 801
 802     if (exec->argumentCount() < 2)
 803         return JSValue::encode(unfiltered);
 804
 805     JSValue function = exec->argument(1);
 806     CallData callData;
 807     CallType callType = getCallData(function, callData);
 808     if (callType == CallTypeNone)
 809         return JSValue::encode(unfiltered);
 810     return JSValue::encode(Walker(exec, Local<JSObject>(exec->vm(), asObject(function)), callType, callData).walk(unfiltered));
 811 }
 812
 813 // ECMA-262 v5 15.12.3
 814 EncodedJSValue JSC_HOST_CALL JSONProtoFuncStringify(ExecState* exec)
 815 {
 816     if (!exec->argumentCount())
 817         return throwVMError(exec, createError(exec, ASCIILiteral("No input to stringify")));
 818     LocalScope scope(exec->vm());
 819     Local<Unknown> value(exec->vm(), exec->argument(0));
 820     Local<Unknown> replacer(exec->vm(), exec->argument(1));
 821     Local<Unknown> space(exec->vm(), exec->argument(2));
 822     return JSValue::encode(Stringifier(exec, replacer, space).stringify(value).get());
 823 }
 824
 825 String JSONStringify(ExecState* exec, JSValue value, unsigned indent)
 826 {
 827     LocalScope scope(exec->vm());
 828     Local<Unknown> result = Stringifier(exec, Local<Unknown>(exec->vm(), jsNull()), Local<Unknown>(exec->vm(), jsNumber(indent))).stringify(Local<Unknown>(exec->vm(), value));
 829     if (result.isUndefinedOrNull())
 830         return String();
 831     return result.getString(exec);
 832 }
 833
 834 } // namespace JSC