De-virtualize destructors
[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 void Structure::destroy(JSCell* cell)
222 {
223     jsCast<Structure*>(cell)->Structure::~Structure();
224 }
225
226 void Structure::materializePropertyMap(JSGlobalData& globalData)
227 {
228     ASSERT(structure()->classInfo() == &s_info);
229     ASSERT(!m_propertyTable);
230
231     Vector<Structure*, 8> structures;
232     structures.append(this);
233
234     Structure* structure = this;
235
236     // Search for the last Structure with a property table.
237     while ((structure = structure->previousID())) {
238         if (structure->m_isPinnedPropertyTable) {
239             ASSERT(structure->m_propertyTable);
240             ASSERT(!structure->m_previous);
241
242             m_propertyTable = structure->m_propertyTable->copy(globalData, 0, m_offset + 1);
243             break;
244         }
245
246         structures.append(structure);
247     }
248
249     if (!m_propertyTable)
250         createPropertyMap(m_offset + 1);
251
252     for (ptrdiff_t i = structures.size() - 2; i >= 0; --i) {
253         structure = structures[i];
254         PropertyMapEntry entry(globalData, this, structure->m_nameInPrevious.get(), structure->m_offset, structure->m_attributesInPrevious, structure->m_specificValueInPrevious.get());
255         m_propertyTable->add(entry);
256     }
257 }
258
259 void Structure::growPropertyStorageCapacity()
260 {
261     if (isUsingInlineStorage())
262         m_propertyStorageCapacity = JSObject::baseExternalStorageCapacity;
263     else
264         m_propertyStorageCapacity *= 2;
265 }
266
267 void Structure::despecifyDictionaryFunction(JSGlobalData& globalData, const Identifier& propertyName)
268 {
269     StringImpl* rep = propertyName.impl();
270
271     materializePropertyMapIfNecessary(globalData);
272
273     ASSERT(isDictionary());
274     ASSERT(m_propertyTable);
275
276     PropertyMapEntry* entry = m_propertyTable->find(rep).first;
277     ASSERT(entry);
278     entry->specificValue.clear();
279 }
280
281 Structure* Structure::addPropertyTransitionToExistingStructure(Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
282 {
283     ASSERT(!structure->isDictionary());
284     ASSERT(structure->isObject());
285
286     if (Structure* existingTransition = structure->m_transitionTable.get(propertyName.impl(), attributes)) {
287         JSCell* specificValueInPrevious = existingTransition->m_specificValueInPrevious.get();
288         if (specificValueInPrevious && specificValueInPrevious != specificValue)
289             return 0;
290         ASSERT(existingTransition->m_offset != noOffset);
291         offset = existingTransition->m_offset;
292         return existingTransition;
293     }
294
295     return 0;
296 }
297
298 Structure* Structure::addPropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset)
299 {
300     // If we have a specific function, we may have got to this point if there is
301     // already a transition with the correct property name and attributes, but
302     // specialized to a different function.  In this case we just want to give up
303     // and despecialize the transition.
304     // In this case we clear the value of specificFunction which will result
305     // in us adding a non-specific transition, and any subsequent lookup in
306     // Structure::addPropertyTransitionToExistingStructure will just use that.
307     if (specificValue && structure->m_transitionTable.contains(propertyName.impl(), attributes))
308         specificValue = 0;
309
310     ASSERT(!structure->isDictionary());
311     ASSERT(structure->isObject());
312     ASSERT(!Structure::addPropertyTransitionToExistingStructure(structure, propertyName, attributes, specificValue, offset));
313     
314     if (structure->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
315         specificValue = 0;
316
317     if (structure->transitionCount() > s_maxTransitionLength) {
318         Structure* transition = toCacheableDictionaryTransition(globalData, structure);
319         ASSERT(structure != transition);
320         offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
321         if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
322             transition->growPropertyStorageCapacity();
323         return transition;
324     }
325
326     Structure* transition = create(globalData, structure);
327
328     transition->m_cachedPrototypeChain.setMayBeNull(globalData, transition, structure->m_cachedPrototypeChain.get());
329     transition->m_previous.set(globalData, transition, structure);
330     transition->m_nameInPrevious = propertyName.impl();
331     transition->m_attributesInPrevious = attributes;
332     transition->m_specificValueInPrevious.setMayBeNull(globalData, transition, specificValue);
333
334     if (structure->m_propertyTable) {
335         if (structure->m_isPinnedPropertyTable)
336             transition->m_propertyTable = structure->m_propertyTable->copy(globalData, transition, structure->m_propertyTable->size() + 1);
337         else
338             transition->m_propertyTable = structure->m_propertyTable.release();
339     } else {
340         if (structure->m_previous)
341             transition->materializePropertyMap(globalData);
342         else
343             transition->createPropertyMap();
344     }
345
346     offset = transition->putSpecificValue(globalData, propertyName, attributes, specificValue);
347     if (transition->propertyStorageSize() > transition->propertyStorageCapacity())
348         transition->growPropertyStorageCapacity();
349
350     transition->m_offset = offset;
351     structure->m_transitionTable.add(globalData, transition);
352     return transition;
353 }
354
355 Structure* Structure::removePropertyTransition(JSGlobalData& globalData, Structure* structure, const Identifier& propertyName, size_t& offset)
356 {
357     ASSERT(!structure->isUncacheableDictionary());
358
359     Structure* transition = toUncacheableDictionaryTransition(globalData, structure);
360
361     offset = transition->remove(propertyName);
362
363     return transition;
364 }
365
366 Structure* Structure::changePrototypeTransition(JSGlobalData& globalData, Structure* structure, JSValue prototype)
367 {
368     Structure* transition = create(globalData, structure);
369
370     transition->m_prototype.set(globalData, transition, prototype);
371
372     // Don't set m_offset, as one can not transition to this.
373
374     structure->materializePropertyMapIfNecessary(globalData);
375     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
376     transition->pin();
377
378     return transition;
379 }
380
381 Structure* Structure::despecifyFunctionTransition(JSGlobalData& globalData, Structure* structure, const Identifier& replaceFunction)
382 {
383     ASSERT(structure->m_specificFunctionThrashCount < maxSpecificFunctionThrashCount);
384     Structure* transition = create(globalData, structure);
385
386     ++transition->m_specificFunctionThrashCount;
387
388     // Don't set m_offset, as one can not transition to this.
389
390     structure->materializePropertyMapIfNecessary(globalData);
391     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
392     transition->pin();
393
394     if (transition->m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
395         transition->despecifyAllFunctions(globalData);
396     else {
397         bool removed = transition->despecifyFunction(globalData, replaceFunction);
398         ASSERT_UNUSED(removed, removed);
399     }
400
401     return transition;
402 }
403
404 Structure* Structure::getterSetterTransition(JSGlobalData& globalData, Structure* structure)
405 {
406     Structure* transition = create(globalData, structure);
407
408     // Don't set m_offset, as one can not transition to this.
409
410     structure->materializePropertyMapIfNecessary(globalData);
411     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
412     transition->pin();
413
414     return transition;
415 }
416
417 Structure* Structure::toDictionaryTransition(JSGlobalData& globalData, Structure* structure, DictionaryKind kind)
418 {
419     ASSERT(!structure->isUncacheableDictionary());
420     
421     Structure* transition = create(globalData, structure);
422
423     structure->materializePropertyMapIfNecessary(globalData);
424     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
425     transition->m_dictionaryKind = kind;
426     transition->pin();
427
428     return transition;
429 }
430
431 Structure* Structure::toCacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
432 {
433     return toDictionaryTransition(globalData, structure, CachedDictionaryKind);
434 }
435
436 Structure* Structure::toUncacheableDictionaryTransition(JSGlobalData& globalData, Structure* structure)
437 {
438     return toDictionaryTransition(globalData, structure, UncachedDictionaryKind);
439 }
440
441 // In future we may want to cache this transition.
442 Structure* Structure::sealTransition(JSGlobalData& globalData, Structure* structure)
443 {
444     Structure* transition = preventExtensionsTransition(globalData, structure);
445
446     if (transition->m_propertyTable) {
447         PropertyTable::iterator end = transition->m_propertyTable->end();
448         for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
449             iter->attributes |= DontDelete;
450     }
451
452     return transition;
453 }
454
455 // In future we may want to cache this transition.
456 Structure* Structure::freezeTransition(JSGlobalData& globalData, Structure* structure)
457 {
458     Structure* transition = preventExtensionsTransition(globalData, structure);
459
460     if (transition->m_propertyTable) {
461         PropertyTable::iterator end = transition->m_propertyTable->end();
462         for (PropertyTable::iterator iter = transition->m_propertyTable->begin(); iter != end; ++iter)
463             iter->attributes |= (DontDelete | ReadOnly);
464     }
465
466     return transition;
467 }
468
469 // In future we may want to cache this transition.
470 Structure* Structure::preventExtensionsTransition(JSGlobalData& globalData, Structure* structure)
471 {
472     Structure* transition = create(globalData, structure);
473
474     // Don't set m_offset, as one can not transition to this.
475
476     structure->materializePropertyMapIfNecessary(globalData);
477     transition->m_propertyTable = structure->copyPropertyTableForPinning(globalData, transition);
478     transition->m_preventExtensions = true;
479     transition->pin();
480
481     return transition;
482 }
483
484 // In future we may want to cache this property.
485 bool Structure::isSealed(JSGlobalData& globalData)
486 {
487     if (isExtensible())
488         return false;
489
490     materializePropertyMapIfNecessary(globalData);
491     if (!m_propertyTable)
492         return true;
493
494     PropertyTable::iterator end = m_propertyTable->end();
495     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
496         if ((iter->attributes & DontDelete) != DontDelete)
497             return false;
498     }
499     return true;
500 }
501
502 // In future we may want to cache this property.
503 bool Structure::isFrozen(JSGlobalData& globalData)
504 {
505     if (isExtensible())
506         return false;
507
508     materializePropertyMapIfNecessary(globalData);
509     if (!m_propertyTable)
510         return true;
511
512     PropertyTable::iterator end = m_propertyTable->end();
513     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
514         if ((iter->attributes & (DontDelete | ReadOnly)) != (DontDelete | ReadOnly))
515             return false;
516     }
517     return true;
518 }
519
520 Structure* Structure::flattenDictionaryStructure(JSGlobalData& globalData, JSObject* object)
521 {
522     ASSERT(isDictionary());
523     if (isUncacheableDictionary()) {
524         ASSERT(m_propertyTable);
525
526         size_t propertyCount = m_propertyTable->size();
527         Vector<JSValue> values(propertyCount);
528
529         unsigned i = 0;
530         PropertyTable::iterator end = m_propertyTable->end();
531         for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter, ++i) {
532             values[i] = object->getDirectOffset(iter->offset);
533             // Update property table to have the new property offsets
534             iter->offset = i;
535         }
536         
537         // Copy the original property values into their final locations
538         for (unsigned i = 0; i < propertyCount; i++)
539             object->putDirectOffset(globalData, i, values[i]);
540
541         m_propertyTable->clearDeletedOffsets();
542     }
543
544     m_dictionaryKind = NoneDictionaryKind;
545     return this;
546 }
547
548 size_t Structure::addPropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
549 {
550     ASSERT(!m_enumerationCache);
551
552     if (m_specificFunctionThrashCount == maxSpecificFunctionThrashCount)
553         specificValue = 0;
554
555     materializePropertyMapIfNecessaryForPinning(globalData);
556     
557     pin();
558
559     size_t offset = putSpecificValue(globalData, propertyName, attributes, specificValue);
560     if (propertyStorageSize() > propertyStorageCapacity())
561         growPropertyStorageCapacity();
562     return offset;
563 }
564
565 size_t Structure::removePropertyWithoutTransition(JSGlobalData& globalData, const Identifier& propertyName)
566 {
567     ASSERT(isUncacheableDictionary());
568     ASSERT(!m_enumerationCache);
569
570     materializePropertyMapIfNecessaryForPinning(globalData);
571
572     pin();
573     size_t offset = remove(propertyName);
574     return offset;
575 }
576
577 void Structure::pin()
578 {
579     ASSERT(m_propertyTable);
580     m_isPinnedPropertyTable = true;
581     m_previous.clear();
582     m_nameInPrevious.clear();
583 }
584
585 #if DUMP_PROPERTYMAP_STATS
586
587 struct PropertyMapStatisticsExitLogger {
588     ~PropertyMapStatisticsExitLogger();
589 };
590
591 static PropertyMapStatisticsExitLogger logger;
592
593 PropertyMapStatisticsExitLogger::~PropertyMapStatisticsExitLogger()
594 {
595     printf("\nJSC::PropertyMap statistics\n\n");
596     printf("%d probes\n", numProbes);
597     printf("%d collisions (%.1f%%)\n", numCollisions, 100.0 * numCollisions / numProbes);
598     printf("%d rehashes\n", numRehashes);
599     printf("%d removes\n", numRemoves);
600 }
601
602 #endif
603
604 #if !DO_PROPERTYMAP_CONSTENCY_CHECK
605
606 inline void Structure::checkConsistency()
607 {
608 }
609
610 #endif
611
612 PassOwnPtr<PropertyTable> Structure::copyPropertyTable(JSGlobalData& globalData, Structure* owner)
613 {
614     return adoptPtr(m_propertyTable ? new PropertyTable(globalData, owner, *m_propertyTable) : 0);
615 }
616
617 PassOwnPtr<PropertyTable> Structure::copyPropertyTableForPinning(JSGlobalData& globalData, Structure* owner)
618 {
619     return adoptPtr(m_propertyTable ? new PropertyTable(globalData, owner, *m_propertyTable) : new PropertyTable(m_offset == noOffset ? 0 : m_offset));
620 }
621
622 size_t Structure::get(JSGlobalData& globalData, StringImpl* propertyName, unsigned& attributes, JSCell*& specificValue)
623 {
624     materializePropertyMapIfNecessary(globalData);
625     if (!m_propertyTable)
626         return WTF::notFound;
627
628     PropertyMapEntry* entry = m_propertyTable->find(propertyName).first;
629     if (!entry)
630         return WTF::notFound;
631
632     attributes = entry->attributes;
633     specificValue = entry->specificValue.get();
634     return entry->offset;
635 }
636
637 bool Structure::despecifyFunction(JSGlobalData& globalData, const Identifier& propertyName)
638 {
639     materializePropertyMapIfNecessary(globalData);
640     if (!m_propertyTable)
641         return false;
642
643     ASSERT(!propertyName.isNull());
644     PropertyMapEntry* entry = m_propertyTable->find(propertyName.impl()).first;
645     if (!entry)
646         return false;
647
648     ASSERT(entry->specificValue);
649     entry->specificValue.clear();
650     return true;
651 }
652
653 void Structure::despecifyAllFunctions(JSGlobalData& globalData)
654 {
655     materializePropertyMapIfNecessary(globalData);
656     if (!m_propertyTable)
657         return;
658
659     PropertyTable::iterator end = m_propertyTable->end();
660     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter)
661         iter->specificValue.clear();
662 }
663
664 size_t Structure::putSpecificValue(JSGlobalData& globalData, const Identifier& propertyName, unsigned attributes, JSCell* specificValue)
665 {
666     ASSERT(!propertyName.isNull());
667     ASSERT(get(globalData, propertyName) == notFound);
668
669     checkConsistency();
670     if (attributes & DontEnum)
671         m_hasNonEnumerableProperties = true;
672
673     StringImpl* rep = propertyName.impl();
674
675     if (!m_propertyTable)
676         createPropertyMap();
677
678     unsigned newOffset;
679
680     if (m_propertyTable->hasDeletedOffset())
681         newOffset = m_propertyTable->getDeletedOffset();
682     else
683         newOffset = m_propertyTable->size();
684
685     m_propertyTable->add(PropertyMapEntry(globalData, this, rep, newOffset, attributes, specificValue));
686
687     checkConsistency();
688     return newOffset;
689 }
690
691 size_t Structure::remove(const Identifier& propertyName)
692 {
693     ASSERT(!propertyName.isNull());
694
695     checkConsistency();
696
697     StringImpl* rep = propertyName.impl();
698
699     if (!m_propertyTable)
700         return notFound;
701
702     PropertyTable::find_iterator position = m_propertyTable->find(rep);
703     if (!position.first)
704         return notFound;
705
706     size_t offset = position.first->offset;
707
708     m_propertyTable->remove(position);
709     m_propertyTable->addDeletedOffset(offset);
710
711     checkConsistency();
712     return offset;
713 }
714
715 void Structure::createPropertyMap(unsigned capacity)
716 {
717     ASSERT(!m_propertyTable);
718
719     checkConsistency();
720     m_propertyTable = adoptPtr(new PropertyTable(capacity));
721     checkConsistency();
722 }
723
724 void Structure::getPropertyNamesFromStructure(JSGlobalData& globalData, PropertyNameArray& propertyNames, EnumerationMode mode)
725 {
726     materializePropertyMapIfNecessary(globalData);
727     if (!m_propertyTable)
728         return;
729
730     bool knownUnique = !propertyNames.size();
731
732     PropertyTable::iterator end = m_propertyTable->end();
733     for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
734         ASSERT(m_hasNonEnumerableProperties || !(iter->attributes & DontEnum));
735         if (!(iter->attributes & DontEnum) || (mode == IncludeDontEnumProperties)) {
736             if (knownUnique)
737                 propertyNames.addKnownUnique(iter->key);
738             else
739                 propertyNames.add(iter->key);
740         }
741     }
742 }
743
744 void Structure::visitChildren(JSCell* cell, SlotVisitor& visitor)
745 {
746     Structure* thisObject = jsCast<Structure*>(cell);
747     ASSERT_GC_OBJECT_INHERITS(thisObject, &s_info);
748     ASSERT(thisObject->structure()->typeInfo().overridesVisitChildren());
749     JSCell::visitChildren(thisObject, visitor);
750     if (thisObject->m_globalObject)
751         visitor.append(&thisObject->m_globalObject);
752     if (!thisObject->isObject())
753         thisObject->m_cachedPrototypeChain.clear();
754     else {
755         if (thisObject->m_prototype)
756             visitor.append(&thisObject->m_prototype);
757         if (thisObject->m_cachedPrototypeChain)
758             visitor.append(&thisObject->m_cachedPrototypeChain);
759     }
760     if (thisObject->m_previous)
761         visitor.append(&thisObject->m_previous);
762     if (thisObject->m_specificValueInPrevious)
763         visitor.append(&thisObject->m_specificValueInPrevious);
764     if (thisObject->m_enumerationCache)
765         visitor.append(&thisObject->m_enumerationCache);
766     if (thisObject->m_propertyTable) {
767         PropertyTable::iterator end = thisObject->m_propertyTable->end();
768         for (PropertyTable::iterator ptr = thisObject->m_propertyTable->begin(); ptr != end; ++ptr) {
769             if (ptr->specificValue)
770                 visitor.append(&ptr->specificValue);
771         }
772     }
773 }
774
775 #if DO_PROPERTYMAP_CONSTENCY_CHECK
776
777 void PropertyTable::checkConsistency()
778 {
779     ASSERT(m_indexSize >= PropertyTable::MinimumTableSize);
780     ASSERT(m_indexMask);
781     ASSERT(m_indexSize == m_indexMask + 1);
782     ASSERT(!(m_indexSize & m_indexMask));
783
784     ASSERT(m_keyCount <= m_indexSize / 2);
785     ASSERT(m_keyCount + m_deletedCount <= m_indexSize / 2);
786     ASSERT(m_deletedCount <= m_indexSize / 4);
787
788     unsigned indexCount = 0;
789     unsigned deletedIndexCount = 0;
790     for (unsigned a = 0; a != m_indexSize; ++a) {
791         unsigned entryIndex = m_index[a];
792         if (entryIndex == PropertyTable::EmptyEntryIndex)
793             continue;
794         if (entryIndex == deletedEntryIndex()) {
795             ++deletedIndexCount;
796             continue;
797         }
798         ASSERT(entryIndex < deletedEntryIndex());
799         ASSERT(entryIndex - 1 <= usedCount());
800         ++indexCount;
801
802         for (unsigned b = a + 1; b != m_indexSize; ++b)
803             ASSERT(m_index[b] != entryIndex);
804     }
805     ASSERT(indexCount == m_keyCount);
806     ASSERT(deletedIndexCount == m_deletedCount);
807
808     ASSERT(!table()[deletedEntryIndex() - 1].key);
809
810     unsigned nonEmptyEntryCount = 0;
811     for (unsigned c = 0; c < usedCount(); ++c) {
812         StringImpl* rep = table()[c].key;
813         if (rep == PROPERTY_MAP_DELETED_ENTRY_KEY)
814             continue;
815         ++nonEmptyEntryCount;
816         unsigned i = rep->existingHash();
817         unsigned k = 0;
818         unsigned entryIndex;
819         while (1) {
820             entryIndex = m_index[i & m_indexMask];
821             ASSERT(entryIndex != PropertyTable::EmptyEntryIndex);
822             if (rep == table()[entryIndex - 1].key)
823                 break;
824             if (k == 0)
825                 k = 1 | doubleHash(rep->existingHash());
826             i += k;
827         }
828         ASSERT(entryIndex == c + 1);
829     }
830
831     ASSERT(nonEmptyEntryCount == m_keyCount);
832 }
833
834 void Structure::checkConsistency()
835 {
836     if (!m_propertyTable)
837         return;
838
839     if (!m_hasNonEnumerableProperties) {
840         PropertyTable::iterator end = m_propertyTable->end();
841         for (PropertyTable::iterator iter = m_propertyTable->begin(); iter != end; ++iter) {
842             ASSERT(!(iter->attributes & DontEnum));
843         }
844     }
845
846     m_propertyTable->checkConsistency();
847 }
848
849 #endif // DO_PROPERTYMAP_CONSTENCY_CHECK
850
851 } // namespace JSC