Source/JavaScriptCore/runtime/Structure.h

/*
 * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#ifndef Structure_h
#define Structure_h

#include "Identifier.h"
#include "JSType.h"
#include "JSValue.h"
#include "PropertyMapHashTable.h"
#include "PropertyNameArray.h"
#include "Protect.h"
#include "StructureTransitionTable.h"
#include "JSTypeInfo.h"
#include "UString.h"
#include "WeakGCPtr.h"
#include <wtf/PassRefPtr.h>
#include <wtf/RefCounted.h>


namespace JSC {

    class MarkStack;
    class PropertyNameArray;
    class PropertyNameArrayData;
    class StructureChain;

    struct ClassInfo;

    enum EnumerationMode {
        ExcludeDontEnumProperties,
        IncludeDontEnumProperties
    };

    class Structure : public RefCounted<Structure> {
    public:
        friend class StructureTransitionTable;
        static PassRefPtr<Structure> create(JSGlobalData&, JSValue prototype, const TypeInfo& typeInfo, unsigned anonymousSlotCount, const ClassInfo* classInfo)
        {
            return adoptRef(new Structure(prototype, typeInfo, anonymousSlotCount, classInfo));
        }

        enum VPtrStealingHackType { VPtrStealingHack };
        static PassRefPtr<Structure> create(VPtrStealingHackType, const ClassInfo* classInfo)
        {
            return adoptRef(new Structure(jsNull(), TypeInfo(UnspecifiedType), 0, classInfo));
        }

        static void startIgnoringLeaks();
        static void stopIgnoringLeaks();

        static void dumpStatistics();

        static PassRefPtr<Structure> addPropertyTransition(Structure*, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset);
        static PassRefPtr<Structure> addPropertyTransitionToExistingStructure(Structure*, const Identifier& propertyName, unsigned attributes, JSCell* specificValue, size_t& offset);
        static PassRefPtr<Structure> removePropertyTransition(Structure*, const Identifier& propertyName, size_t& offset);
        static PassRefPtr<Structure> changePrototypeTransition(Structure*, JSValue prototype);
        static PassRefPtr<Structure> despecifyFunctionTransition(Structure*, const Identifier&);
        static PassRefPtr<Structure> getterSetterTransition(Structure*);
        static PassRefPtr<Structure> toCacheableDictionaryTransition(Structure*);
        static PassRefPtr<Structure> toUncacheableDictionaryTransition(Structure*);
        static PassRefPtr<Structure> sealTransition(Structure*);
        static PassRefPtr<Structure> freezeTransition(Structure*);
        static PassRefPtr<Structure> preventExtensionsTransition(Structure*);

        bool isSealed();
        bool isFrozen();
        bool isExtensible() const { return !m_preventExtensions; }

        PassRefPtr<Structure> flattenDictionaryStructure(JSGlobalData&, JSObject*);

        ~Structure();

        // These should be used with caution.  
        size_t addPropertyWithoutTransition(const Identifier& propertyName, unsigned attributes, JSCell* specificValue);
        size_t removePropertyWithoutTransition(const Identifier& propertyName);
        void setPrototypeWithoutTransition(JSValue prototype) { m_prototype = prototype; }
        
        bool isDictionary() const { return m_dictionaryKind != NoneDictionaryKind; }
        bool isUncacheableDictionary() const { return m_dictionaryKind == UncachedDictionaryKind; }

        const TypeInfo& typeInfo() const { return m_typeInfo; }

        JSValue storedPrototype() const { return m_prototype.get(); }
        DeprecatedPtr<Unknown>* storedPrototypeSlot() { return &m_prototype; }
        JSValue prototypeForLookup(ExecState*) const;
        StructureChain* prototypeChain(ExecState*) const;
        DeprecatedPtr<StructureChain>* cachedPrototypeChainSlot() { return &m_cachedPrototypeChain; }

        Structure* previousID() const { return m_previous.get(); }

        void growPropertyStorageCapacity();
        unsigned propertyStorageCapacity() const { return m_propertyStorageCapacity; }
        unsigned propertyStorageSize() const { return m_anonymousSlotCount + (m_propertyTable ? m_propertyTable->propertyStorageSize() : static_cast<unsigned>(m_offset + 1)); }
        bool isUsingInlineStorage() const;

        size_t get(const Identifier& propertyName);
        size_t get(StringImpl* propertyName, unsigned& attributes, JSCell*& specificValue);
        size_t get(const Identifier& propertyName, unsigned& attributes, JSCell*& specificValue)
        {
            ASSERT(!propertyName.isNull());
            return get(propertyName.impl(), attributes, specificValue);
        }

        bool hasGetterSetterProperties() const { return m_hasGetterSetterProperties; }
        void setHasGetterSetterProperties(bool hasGetterSetterProperties) { m_hasGetterSetterProperties = hasGetterSetterProperties; }

        bool hasNonEnumerableProperties() const { return m_hasNonEnumerableProperties; }

        bool hasAnonymousSlots() const { return !!m_anonymousSlotCount; }
        unsigned anonymousSlotCount() const { return m_anonymousSlotCount; }
        
        bool isEmpty() const { return m_propertyTable ? m_propertyTable->isEmpty() : m_offset == noOffset; }

        void despecifyDictionaryFunction(const Identifier& propertyName);
        void disableSpecificFunctionTracking() { m_specificFunctionThrashCount = maxSpecificFunctionThrashCount; }

        void setEnumerationCache(JSGlobalData&, JSPropertyNameIterator* enumerationCache); // Defined in JSPropertyNameIterator.h.
        void clearEnumerationCache(); // Defined in JSPropertyNameIterator.h.
        JSPropertyNameIterator* enumerationCache(); // Defined in JSPropertyNameIterator.h.
        void getPropertyNames(PropertyNameArray&, EnumerationMode mode);

        const ClassInfo* classInfo() const { return m_classInfo; }

        static void initializeThreading();

        static ptrdiff_t prototypeOffset()
        {
            return OBJECT_OFFSETOF(Structure, m_prototype);
        }

        static ptrdiff_t typeInfoFlagsOffset()
        {
            return OBJECT_OFFSETOF(Structure, m_typeInfo) + TypeInfo::flagsOffset();
        }

        static ptrdiff_t typeInfoTypeOffset()
        {
            return OBJECT_OFFSETOF(Structure, m_typeInfo) + TypeInfo::typeOffset();
        }

    private:
        Structure(JSValue prototype, const TypeInfo&, unsigned anonymousSlotCount, const ClassInfo*);
        Structure(const Structure*);

        static PassRefPtr<Structure> create(const Structure* structure)
        {
            return adoptRef(new Structure(structure));
        }
        
        typedef enum { 
            NoneDictionaryKind = 0,
            CachedDictionaryKind = 1,
            UncachedDictionaryKind = 2
        } DictionaryKind;
        static PassRefPtr<Structure> toDictionaryTransition(Structure*, DictionaryKind);

        size_t put(const Identifier& propertyName, unsigned attributes, JSCell* specificValue);
        size_t remove(const Identifier& propertyName);

        void createPropertyMap(unsigned keyCount = 0);
        void checkConsistency();

        bool despecifyFunction(const Identifier&);
        void despecifyAllFunctions();

        PropertyTable* copyPropertyTable();
        void materializePropertyMap();
        void materializePropertyMapIfNecessary()
        {
            if (!m_propertyTable && m_previous)
                materializePropertyMap();
        }

        signed char transitionCount() const
        {
            // Since the number of transitions is always the same as m_offset, we keep the size of Structure down by not storing both.
            return m_offset == noOffset ? 0 : m_offset + 1;
        }

        bool isValid(ExecState*, StructureChain* cachedPrototypeChain) const;

        static const signed char s_maxTransitionLength = 64;

        static const signed char noOffset = -1;

        static const unsigned maxSpecificFunctionThrashCount = 3;

        TypeInfo m_typeInfo;

        DeprecatedPtr<Unknown> m_prototype;
        mutable DeprecatedPtr<StructureChain> m_cachedPrototypeChain;

        RefPtr<Structure> m_previous;
        RefPtr<StringImpl> m_nameInPrevious;
        JSCell* m_specificValueInPrevious;

        const ClassInfo* m_classInfo;

        StructureTransitionTable m_transitionTable;

        WeakGCPtr<JSPropertyNameIterator> m_enumerationCache;

        OwnPtr<PropertyTable> m_propertyTable;

        uint32_t m_propertyStorageCapacity;

        // m_offset does not account for anonymous slots
        signed char m_offset;

        unsigned m_dictionaryKind : 2;
        bool m_isPinnedPropertyTable : 1;
        bool m_hasGetterSetterProperties : 1;
        bool m_hasNonEnumerableProperties : 1;
#if COMPILER(WINSCW)
        // Workaround for Symbian WINSCW compiler that cannot resolve unsigned type of the declared 
        // bitfield, when used as argument in make_pair() function calls in structure.ccp.
        // This bitfield optimization is insignificant for the Symbian emulator target.
        unsigned m_attributesInPrevious;
#else
        unsigned m_attributesInPrevious : 7;
#endif
        unsigned m_specificFunctionThrashCount : 2;
        unsigned m_anonymousSlotCount : 5;
        unsigned m_preventExtensions : 1;
        // 4 free bits
    };

    inline size_t Structure::get(const Identifier& propertyName)
    {
        materializePropertyMapIfNecessary();
        if (!m_propertyTable)
            return notFound;

        PropertyMapEntry* entry = m_propertyTable->find(propertyName.impl()).first;
        ASSERT(!entry || entry->offset >= m_anonymousSlotCount);
        return entry ? entry->offset : notFound;
    }

} // namespace JSC

#endif // Structure_h