JavaScriptCore/runtime/JSVariableObject.h

/*
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#ifndef JSVariableObject_h
#define JSVariableObject_h

#include "JSObject.h"
#include "Register.h"
#include "SymbolTable.h"
#include "UnusedParam.h"
#include <wtf/OwnArrayPtr.h>
#include <wtf/UnusedParam.h>

namespace JSC {

    class Register;

    class JSVariableObject : public JSObject {
        friend class JIT;

    public:
        SymbolTable& symbolTable() const { return *d->symbolTable; }

        virtual void putWithAttributes(ExecState*, const Identifier&, JSValue, unsigned attributes) = 0;

        virtual bool deleteProperty(ExecState*, const Identifier&);
        virtual void getOwnPropertyNames(ExecState*, PropertyNameArray&, EnumerationMode mode = ExcludeDontEnumProperties);
        
        virtual bool isVariableObject() const;
        virtual bool isDynamicScope(bool& requiresDynamicChecks) const = 0;

        Register& registerAt(int index) const { return d->registers[index]; }

        static PassRefPtr<Structure> createStructure(JSValue prototype)
        {
            return Structure::create(prototype, TypeInfo(ObjectType, StructureFlags), AnonymousSlotCount);
        }
        
    protected:
        static const unsigned StructureFlags = OverridesGetPropertyNames | JSObject::StructureFlags;
        // Subclasses of JSVariableObject can subclass this struct to add data
        // without increasing their own size (since there's a hard limit on the
        // size of a JSCell).
        struct JSVariableObjectData {
            JSVariableObjectData(SymbolTable* symbolTable, Register* registers)
                : symbolTable(symbolTable)
                , registers(registers)
            {
                ASSERT(symbolTable);
            }

            SymbolTable* symbolTable; // Maps name -> offset from "r" in register file.
            Register* registers; // "r" in the register file.
            OwnArrayPtr<Register> registerArray; // Independent copy of registers, used when a variable object copies its registers out of the register file.

        private:
            JSVariableObjectData(const JSVariableObjectData&);
            JSVariableObjectData& operator=(const JSVariableObjectData&);
        };

        JSVariableObject(NonNullPassRefPtr<Structure> structure, JSVariableObjectData* data)
            : JSObject(structure)
            , d(data) // Subclass owns this pointer.
        {
        }

        Register* copyRegisterArray(Register* src, size_t count);
        void setRegisters(Register* r, Register* registerArray);

        bool symbolTableGet(const Identifier&, PropertySlot&);
        bool symbolTableGet(const Identifier&, PropertyDescriptor&);
        bool symbolTableGet(const Identifier&, PropertySlot&, bool& slotIsWriteable);
        bool symbolTablePut(const Identifier&, JSValue);
        bool symbolTablePutWithAttributes(const Identifier&, JSValue, unsigned attributes);

        JSVariableObjectData* d;
    };

    inline bool JSVariableObject::symbolTableGet(const Identifier& propertyName, PropertySlot& slot)
    {
        SymbolTableEntry entry = symbolTable().inlineGet(propertyName.ustring().rep());
        if (!entry.isNull()) {
            slot.setRegisterSlot(&registerAt(entry.getIndex()));
            return true;
        }
        return false;
    }

    inline bool JSVariableObject::symbolTableGet(const Identifier& propertyName, PropertySlot& slot, bool& slotIsWriteable)
    {
        SymbolTableEntry entry = symbolTable().inlineGet(propertyName.ustring().rep());
        if (!entry.isNull()) {
            slot.setRegisterSlot(&registerAt(entry.getIndex()));
            slotIsWriteable = !entry.isReadOnly();
            return true;
        }
        return false;
    }

    inline bool JSVariableObject::symbolTablePut(const Identifier& propertyName, JSValue value)
    {
        ASSERT(!Heap::heap(value) || Heap::heap(value) == Heap::heap(this));

        SymbolTableEntry entry = symbolTable().inlineGet(propertyName.ustring().rep());
        if (entry.isNull())
            return false;
        if (entry.isReadOnly())
            return true;
        registerAt(entry.getIndex()) = value;
        return true;
    }

    inline bool JSVariableObject::symbolTablePutWithAttributes(const Identifier& propertyName, JSValue value, unsigned attributes)
    {
        ASSERT(!Heap::heap(value) || Heap::heap(value) == Heap::heap(this));

        SymbolTable::iterator iter = symbolTable().find(propertyName.ustring().rep());
        if (iter == symbolTable().end())
            return false;
        SymbolTableEntry& entry = iter->second;
        ASSERT(!entry.isNull());
        entry.setAttributes(attributes);
        registerAt(entry.getIndex()) = value;
        return true;
    }

    inline Register* JSVariableObject::copyRegisterArray(Register* src, size_t count)
    {
        Register* registerArray = new Register[count];
        memcpy(registerArray, src, count * sizeof(Register));

        return registerArray;
    }

    inline void JSVariableObject::setRegisters(Register* registers, Register* registerArray)
    {
        ASSERT(registerArray != d->registerArray.get());
        d->registerArray.set(registerArray);
        d->registers = registers;
    }

} // namespace JSC

#endif // JSVariableObject_h