[[Put]] should throw if prototype chain contains a readonly property.
[WebKit-https.git] / Source / JavaScriptCore / runtime / Structure.cpp
1 /*
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25
26 #include "config.h"
27 #include "Structure.h"
28
29 #include "Identifier.h"
30 #include "JSObject.h"
31 #include "JSPropertyNameIterator.h"
32 #include "Lookup.h"
33 #include "PropertyNameArray.h"
34 #include "StructureChain.h"
35 #include <wtf/RefCountedLeakCounter.h>
36 #include <wtf/RefPtr.h>
37 #include <wtf/Threading.h>
38
39 #define DUMP_STRUCTURE_ID_STATISTICS 0
40
41 #ifndef NDEBUG
42 #define DO_PROPERTYMAP_CONSTENCY_CHECK 0
43 #else
44 #define DO_PROPERTYMAP_CONSTENCY_CHECK 0
45 #endif
46
47 using namespace std;
48 using namespace WTF;
49
50 #if DUMP_PROPERTYMAP_STATS
51
52 int numProbes;
53 int numCollisions;
54 int numRehashes;
55 int numRemoves;
56
57 #endif
58
59 namespace JSC {
60
61 #if DUMP_STRUCTURE_ID_STATISTICS
62 static HashSet<Structure*>& liveStructureSet = *(new HashSet<Structure*>);
63 #endif
64
65 bool StructureTransitionTable::contains(StringImpl* rep, unsigned attributes) const
66 {
67     if (isUsingSingleSlot()) {
68         Structure* transition = singleTransition();
69         return transition && transition->m_nameInPrevious == rep && transition->m_attributesInPrevious == attributes;
70     }
71     return map()->contains(make_pair(rep, attributes));
72 }
73
74 inline Structure* StructureTransitionTable::get(StringImpl* rep, unsigned attributes) const
75 {
76     if (isUsingSingleSlot()) {
77         Structure* transition = singleTransition();
78         return (transition && transition->m_nameInPrevious == rep && transition->m_attributesInPrevious == attributes) ? transition : 0;
79     }
80     return map()->get(make_pair(rep, attributes));
81 }
82
83 inline void StructureTransitionTable::add(JSGlobalData& globalData, Structure* structure)
84 {
85     if (isUsingSingleSlot()) {
86         Structure* existingTransition = singleTransition();
87
88         // This handles the first transition being added.
89         if (!existingTransition) {
90             setSingleTransition(globalData, structure);
91             return;
92         }
93
94         // This handles the second transition being added
95         // (or the first transition being despecified!)
96         setMap(new TransitionMap());
97         add(globalData, existingTransition);
98     }
99
100     // Add the structure to the map.
101
102     // Newer versions of the STL have an std::make_pair function that takes rvalue references.
103     // When either of the parameters are bitfields, the C++ compiler will try to bind them as lvalues, which is invalid. To work around this, use unary "+" to make the parameter an rvalue.
104     // See https://bugs.webkit.org/show_bug.cgi?id=59261 for more details
105     std::pair<TransitionMap::iterator, bool> result = map()->add(globalData, make_pair(structure->m_nameInPrevious, +structure->m_attributesInPrevious), structure);
106     if (!result.second) {
107         // There already is an entry! - we should only hit this when despecifying.
108         ASSERT(result.first.get().second->m_specificValueInPrevious);
109         ASSERT(!structure->m_specificValueInPrevious);
110         map()->set(result.first, structure);
111     }
112 }
113
114 void Structure::dumpStatistics()
115 {
116 #if DUMP_STRUCTURE_ID_STATISTICS
117     unsigned numberLeaf = 0;
118     unsigned numberUsingSingleSlot = 0;
119     unsigned numberSingletons = 0;
120     unsigned numberWithPropertyMaps = 0;
121     unsigned totalPropertyMapsSize = 0;
122
123     HashSet<Structure*>::const_iterator end = liveStructureSet.end();
124     for (HashSet<Structure*>::const_iterator it = liveStructureSet.begin(); it != end; ++it) {
125         Structure* structure = *it;
126
127         switch (structure->m_transitionTable.size()) {
128             case 0:
129                 ++numberLeaf;
130                if (!structure->m_previous)
131                     ++numberSingletons;
132                 break;
133
134             case 1:
135                 ++numberUsingSingleSlot;
136                 break;
137         }
138
139         if (structure->m_propertyTable) {
140             ++numberWithPropertyMaps;
141             totalPropertyMapsSize += structure->m_propertyTable->sizeInMemory();
142         }
143     }
144
145     dataLog("Number of live Structures: %d\n", liveStructureSet.size());
146     dataLog("Number of Structures using the single item optimization for transition map: %d\n", numberUsingSingleSlot);
147     dataLog("Number of Structures that are leaf nodes: %d\n", numberLeaf);
148     dataLog("Number of Structures that singletons: %d\n", numberSingletons);
149     dataLog("Number of Structures with PropertyMaps: %d\n", numberWithPropertyMaps);
150
151     dataLog("Size of a single Structures: %d\n", static_cast<unsigned>(sizeof(Structure)));
152     dataLog("Size of sum of all property maps: %d\n", totalPropertyMapsSize);
153     dataLog("Size of average of all property maps: %f\n", static_cast<double>(totalPropertyMapsSize) / static_cast<double>(liveStructureSet.size()));
154 #else
155     dataLog("Dumping Structure statistics is not enabled.\n");
156 #endif
157 }
158
159 Structure::Structure(JSGlobalData& globalData, JSGlobalObject* globalObject, JSValue prototype, const TypeInfo& typeInfo, const ClassInfo* classInfo)
160     : JSCell(globalData, globalData.structureStructure.get())
161     , m_typeInfo(typeInfo)
162     , m_globalObject(globalData, this, globalObject, WriteBarrier<JSGlobalObject>::MayBeNull)
163     , m_prototype(globalData, this, prototype)
164     , m_classInfo(classInfo)
165     , m_propertyStorageCapacity(typeInfo.isFinalObject() ? JSFinalObject_inlineStorageCapacity : JSNonFinalObject_inlineStorageCapacity)
166     , m_offset(noOffset)
167     , m_dictionaryKind(NoneDictionaryKind)
168     , m_isPinnedPropertyTable(false)
169     , m_hasGetterSetterProperties(false)
170     , m_hasReadOnlyGetterSetterPropertiesExcludingProto(false)
171     , m_hasNonEnumerableProperties(false)
172     , m_attributesInPrevious(0)
173     , m_specificFunctionThrashCount(0)
174     , m_preventExtensions(false)
175     , m_didTransition(false)
176     , m_staticFunctionReified(false)
177 {
178 }
179
180 const ClassInfo Structure::s_info = { "Structure", 0, 0, 0, CREATE_METHOD_TABLE(Structure) };
181
182 Structure::Structure(JSGlobalData& globalData)
183     : JSCell(CreatingEarlyCell)
184     , m_typeInfo(CompoundType, OverridesVisitChildren)
185     , m_prototype(globalData, this, jsNull())
186     , m_classInfo(&s_info)
187     , m_propertyStorageCapacity(0)
188     , m_offset(noOffset)
189     , m_dictionaryKind(NoneDictionaryKind)
190     , m_isPinnedPropertyTable(false)
191     , m_hasGetterSetterProperties(false)
192     , m_hasReadOnlyGetterSetterPropertiesExcludingProto(false)
193     , m_hasNonEnumerableProperties(false)
194     , m_attributesInPrevious(0)
195     , m_specificFunctionThrashCount(0)
196     , m_preventExtensions(false)
197     , m_didTransition(false)
198     , m_staticFunctionReified(false)
199 {
200 }
201
202 Structure::Structure(JSGlobalData& globalData, const Structure* previous)
203     : JSCell(globalData, globalData.structureStructure.get())
204     , m_typeInfo(previous->typeInfo())
205     , m_prototype(globalData, this, previous->storedPrototype())
206     , m_classInfo(previous->m_classInfo)
207     , m_propertyStorageCapacity(previous->m_propertyStorageCapacity)
208     , m_offset(noOffset)
209     , m_dictionaryKind(previous->m_dictionaryKind)
210     , m_isPinnedPropertyTable(false)
211     , m_hasGetterSetterProperties(previous->m_hasGetterSetterProperties)
212     , m_hasReadOnlyGetterSetterPropertiesExcludingProto(previous->m_hasReadOnlyGetterSetterPropertiesExcludingProto)
213     , m_hasNonEnumerableProperties(previous->m_hasNonEnumerableProperties)
214     , m_attributesInPrevious(0)
215     , m_specificFunctionThrashCount(previous->m_specificFunctionThrashCount)
216     , m_preventExtensions(previous->m_preventExtensions)
217     , m_didTransition(true)
218     , m_staticFunctionReified(previous->m_staticFunctionReified)
219 {
220     if (previous->m_globalObject)
221         m_globalObject.set(globalData, this, previous->m_globalObject.get());
222 }
223
224 void Structure::destroy(JSCell* cell)
225 {
226     jsCast<Structure*>(cell)->Structure::~Structure();
227 }
228
229 void Structure::materializePropertyMap(JSGlobalData& globalData)
230 {
231     ASSERT(structure()->classInfo() == &s_info);
232     ASSERT(!m_propertyTable);
233
234     Vector<Structure*, 8> structures;
235     structures.append(this);
236
237     Structure* structure = this;
238
239     // Search for the last Structure with a property table.
240     while ((structure = structure->previousID())) {
241         if (structure->m_isPinnedPropertyTable) {
242             ASSERT(structure->m_propertyTable);
243             ASSERT(!structure->m_previous);
244
245             m_propertyTable = structure->m_propertyTable->copy(globalData, 0, m_offset + 1);
246             break;
247         }
248
249         structures.append(structure);
250     }
251
252     if (!m_propertyTable)
253         createPropertyMap(m_offset + 1);
254
255     for (ptrdiff_t i = structures.size() - 2; i >= 0; --i) {
256         structure = structures[i];
257         PropertyMapEntry entry(globalData, this, structure->m_nameInPrevious.get(), structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious.get());
258         m_propertyTable->add(entry);
259     }
260 }
261
262 void Structure::growPropertyStorageCapacity()
263 {
264     if (isUsingInlineStorage())
265         m_propertyStorageCapacity = JSObject::baseExternalStorageCapacity;
266     else
267         m_propertyStorageCapacity *= 2;
268 }
269
270 void Structure::despecifyDictionaryFunction(JSGlobalData& globalData, const Identifier& propertyName)
271 {
272     StringImpl* rep = propertyName.impl();
273
274     materializePropertyMapIfNecessary(globalData);
275
276     ASSERT(isDictionary());
277     ASSERT(m_propertyTable);
278
279     PropertyMapEntry* entry = m_propertyTable->find(rep).first;
280     ASSERT(entry);
281     entry->specificValue.clear();
282 }
283
284 Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
285 {
286     ASSERT(!structure->isDictionary());
287     ASSERT(structure->isObject());
288
289     if (Structure* existingTransition = structure->m_transitionTable.get(propertyName.impl(), attributes)) {
290         JSCell* specificValueInPrevious = existingTransition->m_specificValueInPrevious.get();
291         if (specificValueInPrevious && specificValueInPrevious != specificValue)
292             return 0;
293         ASSERT(existingTransition->m_offset != noOffset);
294         offset = existingTransition->m_offset;
295         return existingTransition;
296     }
297
298     return 0;
299 }
300
301 Structure* Structure::addPropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
302 {
303     // If we have a specific function, we may have got to this point if there is
304     // already a transition with the correct property name and attributes, but
305     // specialized to a different function.  In this case we just want to give up
306     // and despecialize the transition.
307     // In this case we clear the value of specificFunction which will result
308     // in us adding a non-specific transition, and any subsequent lookup in
309     // Structure::addPropertyTransitionToExistingStructure will just use that.
310     if (specificValue && structure->m_transitionTable.contains(propertyName.impl(), attributes))
311         specificValue = 0;
312
313     ASSERT(!structure->isDictionary());
314     ASSERT(structure->isObject());
315     ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, specificValue, offset));
316     
317     if (structure->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
318         specificValue = 0;
319
320     if (structure->transitionCount() > s_maxTransitionLength) {
321         Structure* transition = toCacheableDictionaryTransition(globalData, structure);
322         ASSERT(structure != transition);
323         offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
324         if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
325             transition->growPropertyStorageCapacity();
326         return transition;
327     }
328
329     Structure* transition = create(globalData, structure);
330
331     transition->m_cachedPrototypeChain.setMayBeNull(globalData, transition, structure->m_cachedPrototypeChain.get());
332     transition->m_previous.set(globalData, transition, structure);
333     transition->m_nameInPrevious = propertyName.impl();
334     transition->m_attributesInPrevious = attributes;
335     transition->m_specificValueInPrevious.setMayBeNull(globalData, transition, specificValue);
336
337     if (structure->m_propertyTable) {
338         if (structure->m_isPinnedPropertyTable)
339             transition->m_propertyTable = structure->m_propertyTable->copy(globalData, transition, structure->m_propertyTable->size() + 1);
340         else
341             transition->m_propertyTable = structure->m_propertyTable.release();
342     } else {
343         if (structure->m_previous)
344             transition->materializePropertyMap(globalData);
345         else
346             transition->createPropertyMap();
347     }
348
349     offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
350     if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
351         transition->growPropertyStorageCapacity();
352
353     transition->m_offset = offset;
354     structure->m_transitionTable.add(globalData, transition);
355     return transition;
356 }
357
358 Structure* Structure::removePropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, size_t& offset)
359 {
360     ASSERT(!structure->isUncacheableDictionary());
361
362     Structure* transition = toUncacheableDictionaryTransition(globalData, structure);
363
364     offset = transition->remove(propertyName);
365
366     return transition;
367 }
368
369 Structure* Structure::changePrototypeTransition(JSGlobalData& globalData, Structure* structure, JSValue prototype)
370 {
371     Structure* transition = create(globalData, structure);
372
373     transition->m_prototype.set(globalData, transition, prototype);
374
375     // Don't set m_offset, as one can not transition to this.
376
377     structure->materializePropertyMapIfNecessary(globalData);
378     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
379     transition->pin();
380
381     return transition;
382 }
383
384 Structure* Structure::despecifyFunctionTransition(JSGlobalData& globalData, Structure* structure, const Identifier& replaceFunction)
385 {
386     ASSERT(structure->m_specificFunctionThrashCount < maxSpecificFunctionThrashCount);
387     Structure* transition = create(globalData, structure);
388
389     ++transition->m_specificFunctionThrashCount;
390
391     // Don't set m_offset, as one can not transition to this.
392
393     structure->materializePropertyMapIfNecessary(globalData);
394     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
395     transition->pin();
396
397     if (transition->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
398         transition->despecifyAllFunctions(globalData);
399     else {
400         bool removed = transition->despecifyFunction(globalData, replaceFunction);
401         ASSERT_UNUSED(removed, removed);
402     }
403
404     return transition;
405 }
406
407 Structure* Structure::attributeChangeTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, unsigned attributes)
408 {
409     if (!structure->isUncacheableDictionary()) {
410         Structure* transition = create(globalData, structure);
411
412         // Don't set m_offset, as one can not transition to this.
413
414         structure->materializePropertyMapIfNecessary(globalData);
415         transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
416         transition->pin();
417         
418         structure = transition;
419     }
420
421     ASSERT(structure->m_propertyTable);
422     PropertyMapEntry* entry = structure->m_propertyTable->find(propertyName.impl()).first;
423     ASSERT(entry);
424     entry->attributes = attributes;
425
426     return structure;
427 }
428
429 Structure* Structure::toDictionaryTransition(JSGlobalData& globalData, Structure* structure, DictionaryKind kind)
430 {
431     ASSERT(!structure->isUncacheableDictionary());
432     
433     Structure* transition = create(globalData, structure);
434
435     structure->materializePropertyMapIfNecessary(globalData);
436     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
437     transition->m_dictionaryKind = kind;
438     transition->pin();
439
440     return transition;
441 }
442
443 Structure* Structure::toCacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
444 {
445     return toDictionaryTransition(globalData, structure, CachedDictionaryKind);
446 }
447
448 Structure* Structure::toUncacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
449 {
450     return toDictionaryTransition(globalData, structure, UncachedDictionaryKind);
451 }
452
453 // In future we may want to cache this transition.
454 Structure* Structure::sealTransition(JSGlobalData& globalData, Structure* structure)
455 {
456     Structure* transition = preventExtensionsTransition(globalData, structure);
457
458     if (transition->m_propertyTable) {
459         PropertyTable::iterator end = transition->m_propertyTable->end();
460         for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
461             iter->attributes |= DontDelete;
462     }
463
464     return transition;
465 }
466
467 // In future we may want to cache this transition.
468 Structure* Structure::freezeTransition(JSGlobalData& globalData, Structure* structure)
469 {
470     Structure* transition = preventExtensionsTransition(globalData, structure);
471
472     if (transition->m_propertyTable) {
473         PropertyTable::iterator end = transition->m_propertyTable->end();
474         for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
475             iter->attributes |= iter->attributes & Accessor ? DontDelete : (DontDelete | ReadOnly);
476     }
477
478     return transition;
479 }
480
481 // In future we may want to cache this transition.
482 Structure* Structure::preventExtensionsTransition(JSGlobalData& globalData, Structure* structure)
483 {
484     Structure* transition = create(globalData, structure);
485
486     // Don't set m_offset, as one can not transition to this.
487
488     structure->materializePropertyMapIfNecessary(globalData);
489     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
490     transition->m_preventExtensions = true;
491     transition->pin();
492
493     return transition;
494 }
495
496 // In future we may want to cache this property.
497 bool Structure::isSealed(JSGlobalData& globalData)
498 {
499     if (isExtensible())
500         return false;
501
502     materializePropertyMapIfNecessary(globalData);
503     if (!m_propertyTable)
504         return true;
505
506     PropertyTable::iterator end = m_propertyTable->end();
507     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
508         if ((iter->attributes & DontDelete) != DontDelete)
509             return false;
510     }
511     return true;
512 }
513
514 // In future we may want to cache this property.
515 bool Structure::isFrozen(JSGlobalData& globalData)
516 {
517     if (isExtensible())
518         return false;
519
520     materializePropertyMapIfNecessary(globalData);
521     if (!m_propertyTable)
522         return true;
523
524     PropertyTable::iterator end = m_propertyTable->end();
525     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
526         if (!(iter->attributes & DontDelete))
527             return false;
528         if (!(iter->attributes & (ReadOnly | Accessor)))
529             return false;
530     }
531     return true;
532 }
533
534 Structure* Structure::flattenDictionaryStructure(JSGlobalData& globalData, JSObject* object)
535 {
536     ASSERT(isDictionary());
537     if (isUncacheableDictionary()) {
538         ASSERT(m_propertyTable);
539
540         size_t propertyCount = m_propertyTable->size();
541         Vector<JSValue> values(propertyCount);
542
543         unsigned i = 0;
544         PropertyTable::iterator end = m_propertyTable->end();
545         for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter, ++i) {
546             values[i] = object->getDirectOffset(iter->offset);
547             // Update property table to have the new property offsets
548             iter->offset = i;
549         }
550         
551         // Copy the original property values into their final locations
552         for (unsigned i = 0; i < propertyCount; i++)
553             object->putDirectOffset(globalData, i, values[i]);
554
555         m_propertyTable->clearDeletedOffsets();
556     }
557
558     m_dictionaryKind = NoneDictionaryKind;
559     return this;
560 }
561
562 size_t Structure::addPropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
563 {
564     ASSERT(!m_enumerationCache);
565
566     if (m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
567         specificValue = 0;
568
569     materializePropertyMapIfNecessaryForPinning(globalData);
570     
571     pin();
572
573     size_t offset = putSpecificValue(globalData, propertyName, attributes, specificValue);
574     if (propertyStorageSize() > propertyStorageCapacity())
575         growPropertyStorageCapacity();
576     return offset;
577 }
578
579 size_t Structure::removePropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName)
580 {
581     ASSERT(isUncacheableDictionary());
582     ASSERT(!m_enumerationCache);
583
584     materializePropertyMapIfNecessaryForPinning(globalData);
585
586     pin();
587     size_t offset = remove(propertyName);
588     return offset;
589 }
590
591 void Structure::pin()
592 {
593     ASSERT(m_propertyTable);
594     m_isPinnedPropertyTable = true;
595     m_previous.clear();
596     m_nameInPrevious.clear();
597 }
598
599 #if DUMP_PROPERTYMAP_STATS
600
601 struct PropertyMapStatisticsExitLogger {
602     ~PropertyMapStatisticsExitLogger();
603 };
604
605 static PropertyMapStatisticsExitLogger logger;
606
607 PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
608 {
609     dataLog("\nJSC::PropertyMap statistics\n\n");
610     dataLog("%d probes\n", numProbes);
611     dataLog("%d collisions (%.1f%%)\n", numCollisions, 100.0 * numCollisions / numProbes);
612     dataLog("%d rehashes\n", numRehashes);
613     dataLog("%d removes\n", numRemoves);
614 }
615
616 #endif
617
618 #if !DO_PROPERTYMAP_CONSTENCY_CHECK
619
620 inline void Structure::checkConsistency()
621 {
622 }
623
624 #endif
625
626 PassOwnPtr<PropertyTable> Structure::copyPropertyTable(JSGlobalData& globalData, Structure* owner)
627 {
628     return adoptPtr(m_propertyTable ? new PropertyTable(globalData, owner, *m_propertyTable) : 0);
629 }
630
631 PassOwnPtr<PropertyTable> Structure::copyPropertyTableForPinning(JSGlobalData& globalData, Structure* owner)
632 {
633     return adoptPtr(m_propertyTable ? new PropertyTable(globalData, owner, *m_propertyTable) : new PropertyTable(m_offset == noOffset ? 0 : m_offset));
634 }
635
636 size_t Structure::get(JSGlobalData& globalData, StringImpl* propertyName, unsigned& attributes, JSCell*& specificValue)
637 {
638     materializePropertyMapIfNecessary(globalData);
639     if (!m_propertyTable)
640         return WTF::notFound;
641
642     PropertyMapEntry* entry = m_propertyTable->find(propertyName).first;
643     if (!entry)
644         return WTF::notFound;
645
646     attributes = entry->attributes;
647     specificValue = entry->specificValue.get();
648     return entry->offset;
649 }
650
651 bool Structure::despecifyFunction(JSGlobalData& globalData, const Identifier& propertyName)
652 {
653     materializePropertyMapIfNecessary(globalData);
654     if (!m_propertyTable)
655         return false;
656
657     ASSERT(!propertyName.isNull());
658     PropertyMapEntry* entry = m_propertyTable->find(propertyName.impl()).first;
659     if (!entry)
660         return false;
661
662     ASSERT(entry->specificValue);
663     entry->specificValue.clear();
664     return true;
665 }
666
667 void Structure::despecifyAllFunctions(JSGlobalData& globalData)
668 {
669     materializePropertyMapIfNecessary(globalData);
670     if (!m_propertyTable)
671         return;
672
673     PropertyTable::iterator end = m_propertyTable->end();
674     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter)
675         iter->specificValue.clear();
676 }
677
678 size_t Structure::putSpecificValue(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
679 {
680     ASSERT(!propertyName.isNull());
681     ASSERT(get(globalData, propertyName) == notFound);
682
683     checkConsistency();
684     if (attributes & DontEnum)
685         m_hasNonEnumerableProperties = true;
686
687     StringImpl* rep = propertyName.impl();
688
689     if (!m_propertyTable)
690         createPropertyMap();
691
692     unsigned newOffset;
693
694     if (m_propertyTable->hasDeletedOffset())
695         newOffset = m_propertyTable->getDeletedOffset();
696     else
697         newOffset = m_propertyTable->size();
698
699     m_propertyTable->add(PropertyMapEntry(globalData, this, rep, newOffset, attributes, specificValue));
700
701     checkConsistency();
702     return newOffset;
703 }
704
705 size_t Structure::remove(const Identifier& propertyName)
706 {
707     ASSERT(!propertyName.isNull());
708
709     checkConsistency();
710
711     StringImpl* rep = propertyName.impl();
712
713     if (!m_propertyTable)
714         return notFound;
715
716     PropertyTable::find_iterator position = m_propertyTable->find(rep);
717     if (!position.first)
718         return notFound;
719
720     size_t offset = position.first->offset;
721
722     m_propertyTable->remove(position);
723     m_propertyTable->addDeletedOffset(offset);
724
725     checkConsistency();
726     return offset;
727 }
728
729 void Structure::createPropertyMap(unsigned capacity)
730 {
731     ASSERT(!m_propertyTable);
732
733     checkConsistency();
734     m_propertyTable = adoptPtr(new PropertyTable(capacity));
735     checkConsistency();
736 }
737
738 void Structure::getPropertyNamesFromStructure(JSGlobalData& globalData, PropertyNameArray& propertyNames, EnumerationMode mode)
739 {
740     materializePropertyMapIfNecessary(globalData);
741     if (!m_propertyTable)
742         return;
743
744     bool knownUnique = !propertyNames.size();
745
746     PropertyTable::iterator end = m_propertyTable->end();
747     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
748         ASSERT(m_hasNonEnumerableProperties || !(iter->attributes & DontEnum));
749         if (!(iter->attributes & DontEnum) || (mode == IncludeDontEnumProperties)) {
750             if (knownUnique)
751                 propertyNames.addKnownUnique(iter->key);
752             else
753                 propertyNames.add(iter->key);
754         }
755     }
756 }
757
758 void Structure::visitChildren(JSCell* cell, SlotVisitor& visitor)
759 {
760     Structure* thisObject = jsCast<Structure*>(cell);
761     ASSERT_GC_OBJECT_INHERITS(thisObject, &s_info);
762     ASSERT(thisObject->structure()->typeInfo().overridesVisitChildren());
763     JSCell::visitChildren(thisObject, visitor);
764     if (thisObject->m_globalObject)
765         visitor.append(&thisObject->m_globalObject);
766     if (!thisObject->isObject())
767         thisObject->m_cachedPrototypeChain.clear();
768     else {
769         if (thisObject->m_prototype)
770             visitor.append(&thisObject->m_prototype);
771         if (thisObject->m_cachedPrototypeChain)
772             visitor.append(&thisObject->m_cachedPrototypeChain);
773     }
774     if (thisObject->m_previous)
775         visitor.append(&thisObject->m_previous);
776     if (thisObject->m_specificValueInPrevious)
777         visitor.append(&thisObject->m_specificValueInPrevious);
778     if (thisObject->m_enumerationCache)
779         visitor.append(&thisObject->m_enumerationCache);
780     if (thisObject->m_propertyTable) {
781         PropertyTable::iterator end = thisObject->m_propertyTable->end();
782         for (PropertyTable::iterator ptr = thisObject->m_propertyTable->begin(); ptr != end; ++ptr) {
783             if (ptr->specificValue)
784                 visitor.append(&ptr->specificValue);
785         }
786     }
787 }
788
789 #if DO_PROPERTYMAP_CONSTENCY_CHECK
790
791 void PropertyTable::checkConsistency()
792 {
793     ASSERT(m_indexSize >= PropertyTable::MinimumTableSize);
794     ASSERT(m_indexMask);
795     ASSERT(m_indexSize == m_indexMask + 1);
796     ASSERT(!(m_indexSize & m_indexMask));
797
798     ASSERT(m_keyCount <= m_indexSize / 2);
799     ASSERT(m_keyCount + m_deletedCount <= m_indexSize / 2);
800     ASSERT(m_deletedCount <= m_indexSize / 4);
801
802     unsigned indexCount = 0;
803     unsigned deletedIndexCount = 0;
804     for (unsigned a = 0; a != m_indexSize; ++a) {
805         unsigned entryIndex = m_index[a];
806         if (entryIndex == PropertyTable::EmptyEntryIndex)
807             continue;
808         if (entryIndex == deletedEntryIndex()) {
809             ++deletedIndexCount;
810             continue;
811         }
812         ASSERT(entryIndex < deletedEntryIndex());
813         ASSERT(entryIndex - 1 <= usedCount());
814         ++indexCount;
815
816         for (unsigned b = a + 1; b != m_indexSize; ++b)
817             ASSERT(m_index[b] != entryIndex);
818     }
819     ASSERT(indexCount == m_keyCount);
820     ASSERT(deletedIndexCount == m_deletedCount);
821
822     ASSERT(!table()[deletedEntryIndex() - 1].key);
823
824     unsigned nonEmptyEntryCount = 0;
825     for (unsigned c = 0; c < usedCount(); ++c) {
826         StringImpl* rep = table()[c].key;
827         if (rep == PROPERTY_MAP_DELETED_ENTRY_KEY)
828             continue;
829         ++nonEmptyEntryCount;
830         unsigned i = rep->existingHash();
831         unsigned k = 0;
832         unsigned entryIndex;
833         while (1) {
834             entryIndex = m_index[i & m_indexMask];
835             ASSERT(entryIndex != PropertyTable::EmptyEntryIndex);
836             if (rep == table()[entryIndex - 1].key)
837                 break;
838             if (k == 0)
839                 k = 1 | doubleHash(rep->existingHash());
840             i += k;
841         }
842         ASSERT(entryIndex == c + 1);
843     }
844
845     ASSERT(nonEmptyEntryCount == m_keyCount);
846 }
847
848 void Structure::checkConsistency()
849 {
850     if (!m_propertyTable)
851         return;
852
853     if (!m_hasNonEnumerableProperties) {
854         PropertyTable::iterator end = m_propertyTable->end();
855         for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
856             ASSERT(!(iter->attributes & DontEnum));
857         }
858     }
859
860     m_propertyTable->checkConsistency();
861 }
862
863 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK
864
865 } // namespace JSC