weex_core/Source/include/JavaScriptCore/runtime/PrototypeMap.h

/*
 * Copyright (C) 2013, 2016-2017 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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#pragma once

#include "IndexingType.h"
#include "JSTypeInfo.h"
#include "WeakGCMap.h"
#include <wtf/TriState.h>

namespace JSC {

class JSGlobalObject;
class JSObject;
class Structure;
class VM;

// Tracks the canonical structure an object should be allocated with when inheriting from a given prototype.
class PrototypeMap {
public:
    explicit PrototypeMap(VM& vm)
        : m_prototypes(vm)
        , m_structures(vm)
    {
    }

    JS_EXPORT_PRIVATE Structure* emptyObjectStructureForPrototype(JSGlobalObject*, JSObject*, unsigned inlineCapacity);
    JS_EXPORT_PRIVATE Structure* emptyStructureForPrototypeFromBaseStructure(JSGlobalObject*, JSObject*, Structure*);
    void clearEmptyObjectStructureForPrototype(JSGlobalObject*, JSObject*, unsigned inlineCapacity);
    JS_EXPORT_PRIVATE void addPrototype(JSObject*);
    inline TriState isPrototype(JSObject*) const; // Returns a conservative estimate.

private:
    Structure* createEmptyStructure(JSGlobalObject*, JSObject* prototype, const TypeInfo&, const ClassInfo*, IndexingType, unsigned inlineCapacity);

    WeakGCMap<JSObject*, JSObject> m_prototypes;
    // FIXME: make the key a struct.
    typedef WeakGCMap<std::tuple<JSObject*, unsigned, const ClassInfo*, JSGlobalObject*>, Structure> StructureMap;
    StructureMap m_structures;
};

} // namespace JSC