Most built-in properties are not deletable
[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     printf("Number of live Structures: %d\n", liveStructureSet.size());
146     printf("Number of Structures using the single item optimization for transition map: %d\n", numberUsingSingleSlot);
147     printf("Number of Structures that are leaf nodes: %d\n", numberLeaf);
148     printf("Number of Structures that singletons: %d\n", numberSingletons);
149     printf("Number of Structures with PropertyMaps: %d\n", numberWithPropertyMaps);
150
151     printf("Size of a single Structures: %d\n", static_cast<unsigned>(sizeof(Structure)));
152     printf("Size of sum of all property maps: %d\n", totalPropertyMapsSize);
153     printf("Size of average of all property maps: %f\n", static_cast<double>(totalPropertyMapsSize) / static_cast<double>(liveStructureSet.size()));
154 #else
155     printf("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_hasNonEnumerableProperties(false)
171     , m_attributesInPrevious(0)
172     , m_specificFunctionThrashCount(0)
173     , m_preventExtensions(false)
174     , m_didTransition(false)
175     , m_staticFunctionReified(false)
176 {
177 }
178
179 const ClassInfo Structure::s_info = { "Structure", 0, 0, 0, CREATE_METHOD_TABLE(Structure) };
180
181 Structure::Structure(JSGlobalData& globalData)
182     : JSCell(CreatingEarlyCell)
183     , m_typeInfo(CompoundType, OverridesVisitChildren)
184     , m_prototype(globalData, this, jsNull())
185     , m_classInfo(&s_info)
186     , m_propertyStorageCapacity(0)
187     , m_offset(noOffset)
188     , m_dictionaryKind(NoneDictionaryKind)
189     , m_isPinnedPropertyTable(false)
190     , m_hasGetterSetterProperties(false)
191     , m_hasNonEnumerableProperties(false)
192     , m_attributesInPrevious(0)
193     , m_specificFunctionThrashCount(0)
194     , m_preventExtensions(false)
195     , m_didTransition(false)
196     , m_staticFunctionReified(false)
197 {
198 }
199
200 Structure::Structure(JSGlobalData& globalData, const Structure* previous)
201     : JSCell(globalData, globalData.structureStructure.get())
202     , m_typeInfo(previous->typeInfo())
203     , m_prototype(globalData, this, previous->storedPrototype())
204     , m_classInfo(previous->m_classInfo)
205     , m_propertyStorageCapacity(previous->m_propertyStorageCapacity)
206     , m_offset(noOffset)
207     , m_dictionaryKind(previous->m_dictionaryKind)
208     , m_isPinnedPropertyTable(false)
209     , m_hasGetterSetterProperties(previous->m_hasGetterSetterProperties)
210     , m_hasNonEnumerableProperties(previous->m_hasNonEnumerableProperties)
211     , m_attributesInPrevious(0)
212     , m_specificFunctionThrashCount(previous->m_specificFunctionThrashCount)
213     , m_preventExtensions(previous->m_preventExtensions)
214     , m_didTransition(true)
215     , m_staticFunctionReified(previous->m_staticFunctionReified)
216 {
217     if (previous->m_globalObject)
218         m_globalObject.set(globalData, this, previous->m_globalObject.get());
219 }
220
221 Structure::~Structure()
222 {
223 }
224
225 void Structure::materializePropertyMap(JSGlobalData& globalData)
226 {
227     ASSERT(structure()->classInfo() == &s_info);
228     ASSERT(!m_propertyTable);
229
230     Vector<Structure*, 8> structures;
231     structures.append(this);
232
233     Structure* structure = this;
234
235     // Search for the last Structure with a property table.
236     while ((structure = structure->previousID())) {
237         if (structure->m_isPinnedPropertyTable) {
238             ASSERT(structure->m_propertyTable);
239             ASSERT(!structure->m_previous);
240
241             m_propertyTable = structure->m_propertyTable->copy(globalData, 0, m_offset + 1);
242             break;
243         }
244
245         structures.append(structure);
246     }
247
248     if (!m_propertyTable)
249         createPropertyMap(m_offset + 1);
250
251     for (ptrdiff_t i = structures.size() - 2; i >= 0; --i) {
252         structure = structures[i];
253         PropertyMapEntry entry(globalData, this, structure->m_nameInPrevious.get(), structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious.get());
254         m_propertyTable->add(entry);
255     }
256 }
257
258 void Structure::growPropertyStorageCapacity()
259 {
260     if (isUsingInlineStorage())
261         m_propertyStorageCapacity = JSObject::baseExternalStorageCapacity;
262     else
263         m_propertyStorageCapacity *= 2;
264 }
265
266 void Structure::despecifyDictionaryFunction(JSGlobalData& globalData, const Identifier& propertyName)
267 {
268     StringImpl* rep = propertyName.impl();
269
270     materializePropertyMapIfNecessary(globalData);
271
272     ASSERT(isDictionary());
273     ASSERT(m_propertyTable);
274
275     PropertyMapEntry* entry = m_propertyTable->find(rep).first;
276     ASSERT(entry);
277     entry->specificValue.clear();
278 }
279
280 Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
281 {
282     ASSERT(!structure->isDictionary());
283     ASSERT(structure->isObject());
284
285     if (Structure* existingTransition = structure->m_transitionTable.get(propertyName.impl(), attributes)) {
286         JSCell* specificValueInPrevious = existingTransition->m_specificValueInPrevious.get();
287         if (specificValueInPrevious && specificValueInPrevious != specificValue)
288             return 0;
289         ASSERT(existingTransition->m_offset != noOffset);
290         offset = existingTransition->m_offset;
291         return existingTransition;
292     }
293
294     return 0;
295 }
296
297 Structure* Structure::addPropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
298 {
299     // If we have a specific function, we may have got to this point if there is
300     // already a transition with the correct property name and attributes, but
301     // specialized to a different function.  In this case we just want to give up
302     // and despecialize the transition.
303     // In this case we clear the value of specificFunction which will result
304     // in us adding a non-specific transition, and any subsequent lookup in
305     // Structure::addPropertyTransitionToExistingStructure will just use that.
306     if (specificValue && structure->m_transitionTable.contains(propertyName.impl(), attributes))
307         specificValue = 0;
308
309     ASSERT(!structure->isDictionary());
310     ASSERT(structure->isObject());
311     ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, specificValue, offset));
312     
313     if (structure->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
314         specificValue = 0;
315
316     if (structure->transitionCount() > s_maxTransitionLength) {
317         Structure* transition = toCacheableDictionaryTransition(globalData, structure);
318         ASSERT(structure != transition);
319         offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
320         if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
321             transition->growPropertyStorageCapacity();
322         return transition;
323     }
324
325     Structure* transition = create(globalData, structure);
326
327     transition->m_cachedPrototypeChain.setMayBeNull(globalData, transition, structure->m_cachedPrototypeChain.get());
328     transition->m_previous.set(globalData, transition, structure);
329     transition->m_nameInPrevious = propertyName.impl();
330     transition->m_attributesInPrevious = attributes;
331     transition->m_specificValueInPrevious.setMayBeNull(globalData, transition, specificValue);
332
333     if (structure->m_propertyTable) {
334         if (structure->m_isPinnedPropertyTable)
335             transition->m_propertyTable = structure->m_propertyTable->copy(globalData, transition, structure->m_propertyTable->size() + 1);
336         else
337             transition->m_propertyTable = structure->m_propertyTable.release();
338     } else {
339         if (structure->m_previous)
340             transition->materializePropertyMap(globalData);
341         else
342             transition->createPropertyMap();
343     }
344
345     offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
346     if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
347         transition->growPropertyStorageCapacity();
348
349     transition->m_offset = offset;
350     structure->m_transitionTable.add(globalData, transition);
351     return transition;
352 }
353
354 Structure* Structure::removePropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, size_t& offset)
355 {
356     ASSERT(!structure->isUncacheableDictionary());
357
358     Structure* transition = toUncacheableDictionaryTransition(globalData, structure);
359
360     offset = transition->remove(propertyName);
361
362     return transition;
363 }
364
365 Structure* Structure::changePrototypeTransition(JSGlobalData& globalData, Structure* structure, JSValue prototype)
366 {
367     Structure* transition = create(globalData, structure);
368
369     transition->m_prototype.set(globalData, transition, prototype);
370
371     // Don't set m_offset, as one can not transition to this.
372
373     structure->materializePropertyMapIfNecessary(globalData);
374     transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
375     transition->pin();
376
377     return transition;
378 }
379
380 Structure* Structure::despecifyFunctionTransition(JSGlobalData& globalData, Structure* structure, const Identifier& replaceFunction)
381 {
382     ASSERT(structure->m_specificFunctionThrashCount < maxSpecificFunctionThrashCount);
383     Structure* transition = create(globalData, structure);
384
385     ++transition->m_specificFunctionThrashCount;
386
387     // Don't set m_offset, as one can not transition to this.
388
389     structure->materializePropertyMapIfNecessary(globalData);
390     transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
391     transition->pin();
392
393     if (transition->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
394         transition->despecifyAllFunctions(globalData);
395     else {
396         bool removed = transition->despecifyFunction(globalData, replaceFunction);
397         ASSERT_UNUSED(removed, removed);
398     }
399
400     return transition;
401 }
402
403 Structure* Structure::getterSetterTransition(JSGlobalData& globalData, Structure* structure)
404 {
405     Structure* transition = create(globalData, structure);
406
407     // Don't set m_offset, as one can not transition to this.
408
409     structure->materializePropertyMapIfNecessary(globalData);
410     transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
411     transition->pin();
412
413     return transition;
414 }
415
416 Structure* Structure::toDictionaryTransition(JSGlobalData& globalData, Structure* structure, DictionaryKind kind)
417 {
418     ASSERT(!structure->isUncacheableDictionary());
419     
420     Structure* transition = create(globalData, structure);
421
422     structure->materializePropertyMapIfNecessary(globalData);
423     transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
424     transition->m_dictionaryKind = kind;
425     transition->pin();
426
427     return transition;
428 }
429
430 Structure* Structure::toCacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
431 {
432     return toDictionaryTransition(globalData, structure, CachedDictionaryKind);
433 }
434
435 Structure* Structure::toUncacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
436 {
437     return toDictionaryTransition(globalData, structure, UncachedDictionaryKind);
438 }
439
440 // In future we may want to cache this transition.
441 Structure* Structure::sealTransition(JSGlobalData& globalData, Structure* structure)
442 {
443     Structure* transition = preventExtensionsTransition(globalData, structure);
444
445     if (transition->m_propertyTable) {
446         PropertyTable::iterator end = transition->m_propertyTable->end();
447         for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
448             iter->attributes |= DontDelete;
449     }
450
451     return transition;
452 }
453
454 // In future we may want to cache this transition.
455 Structure* Structure::freezeTransition(JSGlobalData& globalData, Structure* structure)
456 {
457     Structure* transition = preventExtensionsTransition(globalData, structure);
458
459     if (transition->m_propertyTable) {
460         PropertyTable::iterator end = transition->m_propertyTable->end();
461         for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
462             iter->attributes |= (DontDelete | ReadOnly);
463     }
464
465     return transition;
466 }
467
468 // In future we may want to cache this transition.
469 Structure* Structure::preventExtensionsTransition(JSGlobalData& globalData, Structure* structure)
470 {
471     Structure* transition = create(globalData, structure);
472
473     // Don't set m_offset, as one can not transition to this.
474
475     structure->materializePropertyMapIfNecessary(globalData);
476     transition->m_propertyTable = structure->copyPropertyTable(globalData, transition);
477     transition->m_preventExtensions = true;
478     transition->pin();
479
480     return transition;
481 }
482
483 // In future we may want to cache this property.
484 bool Structure::isSealed(JSGlobalData& globalData)
485 {
486     if (isExtensible())
487         return false;
488
489     materializePropertyMapIfNecessary(globalData);
490     if (!m_propertyTable)
491         return true;
492
493     PropertyTable::iterator end = m_propertyTable->end();
494     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
495         if ((iter->attributes & DontDelete) != DontDelete)
496             return false;
497     }
498     return true;
499 }
500
501 // In future we may want to cache this property.
502 bool Structure::isFrozen(JSGlobalData& globalData)
503 {
504     if (isExtensible())
505         return false;
506
507     materializePropertyMapIfNecessary(globalData);
508     if (!m_propertyTable)
509         return true;
510
511     PropertyTable::iterator end = m_propertyTable->end();
512     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
513         if ((iter->attributes & (DontDelete | ReadOnly)) != (DontDelete | ReadOnly))
514             return false;
515     }
516     return true;
517 }
518
519 Structure* Structure::flattenDictionaryStructure(JSGlobalData& globalData, JSObject* object)
520 {
521     ASSERT(isDictionary());
522     if (isUncacheableDictionary()) {
523         ASSERT(m_propertyTable);
524
525         size_t propertyCount = m_propertyTable->size();
526         Vector<JSValue> values(propertyCount);
527
528         unsigned i = 0;
529         PropertyTable::iterator end = m_propertyTable->end();
530         for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter, ++i) {
531             values[i] = object->getDirectOffset(iter->offset);
532             // Update property table to have the new property offsets
533             iter->offset = i;
534         }
535         
536         // Copy the original property values into their final locations
537         for (unsigned i = 0; i < propertyCount; i++)
538             object->putDirectOffset(globalData, i, values[i]);
539
540         m_propertyTable->clearDeletedOffsets();
541     }
542
543     m_dictionaryKind = NoneDictionaryKind;
544     return this;
545 }
546
547 size_t Structure::addPropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
548 {
549     ASSERT(!m_enumerationCache);
550
551     if (m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
552         specificValue = 0;
553
554     materializePropertyMapIfNecessary(globalData);
555     
556     pin();
557
558     size_t offset = putSpecificValue(globalData, propertyName, attributes, specificValue);
559     if (propertyStorageSize() > propertyStorageCapacity())
560         growPropertyStorageCapacity();
561     return offset;
562 }
563
564 size_t Structure::removePropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName)
565 {
566     ASSERT(isUncacheableDictionary());
567     ASSERT(!m_enumerationCache);
568
569     materializePropertyMapIfNecessary(globalData);
570
571     pin();
572     size_t offset = remove(propertyName);
573     return offset;
574 }
575
576 void Structure::pin()
577 {
578     m_isPinnedPropertyTable = true;
579     m_previous.clear();
580     m_nameInPrevious.clear();
581 }
582
583 #if DUMP_PROPERTYMAP_STATS
584
585 struct PropertyMapStatisticsExitLogger {
586     ~PropertyMapStatisticsExitLogger();
587 };
588
589 static PropertyMapStatisticsExitLogger logger;
590
591 PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
592 {
593     printf("\nJSC::PropertyMap statistics\n\n");
594     printf("%d probes\n", numProbes);
595     printf("%d collisions (%.1f%%)\n", numCollisions, 100.0 * numCollisions / numProbes);
596     printf("%d rehashes\n", numRehashes);
597     printf("%d removes\n", numRemoves);
598 }
599
600 #endif
601
602 #if !DO_PROPERTYMAP_CONSTENCY_CHECK
603
604 inline void Structure::checkConsistency()
605 {
606 }
607
608 #endif
609
610 PassOwnPtr<PropertyTable> Structure::copyPropertyTable(JSGlobalData& globalData, Structure* owner)
611 {
612     return adoptPtr(m_propertyTable ? new PropertyTable(globalData, owner, *m_propertyTable) : 0);
613 }
614
615 size_t Structure::get(JSGlobalData& globalData, StringImpl* propertyName, unsigned& attributes, JSCell*& specificValue)
616 {
617     materializePropertyMapIfNecessary(globalData);
618     if (!m_propertyTable)
619         return WTF::notFound;
620
621     PropertyMapEntry* entry = m_propertyTable->find(propertyName).first;
622     if (!entry)
623         return WTF::notFound;
624
625     attributes = entry->attributes;
626     specificValue = entry->specificValue.get();
627     return entry->offset;
628 }
629
630 bool Structure::despecifyFunction(JSGlobalData& globalData, const Identifier& propertyName)
631 {
632     materializePropertyMapIfNecessary(globalData);
633     if (!m_propertyTable)
634         return false;
635
636     ASSERT(!propertyName.isNull());
637     PropertyMapEntry* entry = m_propertyTable->find(propertyName.impl()).first;
638     if (!entry)
639         return false;
640
641     ASSERT(entry->specificValue);
642     entry->specificValue.clear();
643     return true;
644 }
645
646 void Structure::despecifyAllFunctions(JSGlobalData& globalData)
647 {
648     materializePropertyMapIfNecessary(globalData);
649     if (!m_propertyTable)
650         return;
651
652     PropertyTable::iterator end = m_propertyTable->end();
653     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter)
654         iter->specificValue.clear();
655 }
656
657 size_t Structure::putSpecificValue(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
658 {
659     ASSERT(!propertyName.isNull());
660     ASSERT(get(globalData, propertyName) == notFound);
661
662     checkConsistency();
663     if (attributes & DontEnum)
664         m_hasNonEnumerableProperties = true;
665
666     StringImpl* rep = propertyName.impl();
667
668     if (!m_propertyTable)
669         createPropertyMap();
670
671     unsigned newOffset;
672
673     if (m_propertyTable->hasDeletedOffset())
674         newOffset = m_propertyTable->getDeletedOffset();
675     else
676         newOffset = m_propertyTable->size();
677
678     m_propertyTable->add(PropertyMapEntry(globalData, this, rep, newOffset, attributes, specificValue));
679
680     checkConsistency();
681     return newOffset;
682 }
683
684 size_t Structure::remove(const Identifier& propertyName)
685 {
686     ASSERT(!propertyName.isNull());
687
688     checkConsistency();
689
690     StringImpl* rep = propertyName.impl();
691
692     if (!m_propertyTable)
693         return notFound;
694
695     PropertyTable::find_iterator position = m_propertyTable->find(rep);
696     if (!position.first)
697         return notFound;
698
699     size_t offset = position.first->offset;
700
701     m_propertyTable->remove(position);
702     m_propertyTable->addDeletedOffset(offset);
703
704     checkConsistency();
705     return offset;
706 }
707
708 void Structure::createPropertyMap(unsigned capacity)
709 {
710     ASSERT(!m_propertyTable);
711
712     checkConsistency();
713     m_propertyTable = adoptPtr(new PropertyTable(capacity));
714     checkConsistency();
715 }
716
717 void Structure::getPropertyNames(JSGlobalData& globalData, PropertyNameArray& propertyNames, EnumerationMode mode)
718 {
719     materializePropertyMapIfNecessary(globalData);
720     if (!m_propertyTable)
721         return;
722
723     bool knownUnique = !propertyNames.size();
724
725     PropertyTable::iterator end = m_propertyTable->end();
726     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
727         ASSERT(m_hasNonEnumerableProperties || !(iter->attributes & DontEnum));
728         if (!(iter->attributes & DontEnum) || (mode == IncludeDontEnumProperties)) {
729             if (knownUnique)
730                 propertyNames.addKnownUnique(iter->key);
731             else
732                 propertyNames.add(iter->key);
733         }
734     }
735 }
736
737 void Structure::visitChildren(JSCell* cell, SlotVisitor& visitor)
738 {
739     Structure* thisObject = static_cast<Structure*>(cell);
740     ASSERT_GC_OBJECT_INHERITS(thisObject, &s_info);
741     ASSERT(thisObject->structure()->typeInfo().overridesVisitChildren());
742     JSCell::visitChildren(thisObject, visitor);
743     if (thisObject->m_globalObject)
744         visitor.append(&thisObject->m_globalObject);
745     if (!thisObject->isObject())
746         thisObject->m_cachedPrototypeChain.clear();
747     else {
748         if (thisObject->m_prototype)
749             visitor.append(&thisObject->m_prototype);
750         if (thisObject->m_cachedPrototypeChain)
751             visitor.append(&thisObject->m_cachedPrototypeChain);
752     }
753     if (thisObject->m_previous)
754         visitor.append(&thisObject->m_previous);
755     if (thisObject->m_specificValueInPrevious)
756         visitor.append(&thisObject->m_specificValueInPrevious);
757     if (thisObject->m_enumerationCache)
758         visitor.append(&thisObject->m_enumerationCache);
759     if (thisObject->m_propertyTable) {
760         PropertyTable::iterator end = thisObject->m_propertyTable->end();
761         for (PropertyTable::iterator ptr = thisObject->m_propertyTable->begin(); ptr != end; ++ptr) {
762             if (ptr->specificValue)
763                 visitor.append(&ptr->specificValue);
764         }
765     }
766 }
767
768 #if DO_PROPERTYMAP_CONSTENCY_CHECK
769
770 void PropertyTable::checkConsistency()
771 {
772     ASSERT(m_indexSize >= PropertyTable::MinimumTableSize);
773     ASSERT(m_indexMask);
774     ASSERT(m_indexSize == m_indexMask + 1);
775     ASSERT(!(m_indexSize & m_indexMask));
776
777     ASSERT(m_keyCount <= m_indexSize / 2);
778     ASSERT(m_keyCount + m_deletedCount <= m_indexSize / 2);
779     ASSERT(m_deletedCount <= m_indexSize / 4);
780
781     unsigned indexCount = 0;
782     unsigned deletedIndexCount = 0;
783     for (unsigned a = 0; a != m_indexSize; ++a) {
784         unsigned entryIndex = m_index[a];
785         if (entryIndex == PropertyTable::EmptyEntryIndex)
786             continue;
787         if (entryIndex == deletedEntryIndex()) {
788             ++deletedIndexCount;
789             continue;
790         }
791         ASSERT(entryIndex < deletedEntryIndex());
792         ASSERT(entryIndex - 1 <= usedCount());
793         ++indexCount;
794
795         for (unsigned b = a + 1; b != m_indexSize; ++b)
796             ASSERT(m_index[b] != entryIndex);
797     }
798     ASSERT(indexCount == m_keyCount);
799     ASSERT(deletedIndexCount == m_deletedCount);
800
801     ASSERT(!table()[deletedEntryIndex() - 1].key);
802
803     unsigned nonEmptyEntryCount = 0;
804     for (unsigned c = 0; c < usedCount(); ++c) {
805         StringImpl* rep = table()[c].key;
806         if (rep == PROPERTY_MAP_DELETED_ENTRY_KEY)
807             continue;
808         ++nonEmptyEntryCount;
809         unsigned i = rep->existingHash();
810         unsigned k = 0;
811         unsigned entryIndex;
812         while (1) {
813             entryIndex = m_index[i & m_indexMask];
814             ASSERT(entryIndex != PropertyTable::EmptyEntryIndex);
815             if (rep == table()[entryIndex - 1].key)
816                 break;
817             if (k == 0)
818                 k = 1 | doubleHash(rep->existingHash());
819             i += k;
820         }
821         ASSERT(entryIndex == c + 1);
822     }
823
824     ASSERT(nonEmptyEntryCount == m_keyCount);
825 }
826
827 void Structure::checkConsistency()
828 {
829     if (!m_propertyTable)
830         return;
831
832     if (!m_hasNonEnumerableProperties) {
833         PropertyTable::iterator end = m_propertyTable->end();
834         for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
835             ASSERT(!(iter->attributes & DontEnum));
836         }
837     }
838
839     m_propertyTable->checkConsistency();
840 }
841
842 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK
843
844 } // namespace JSC