Source/JavaScriptCore/runtime/WeakGCMap.h

/*
 * Copyright (C) 2009, 2015-2016 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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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 * 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 INC. OR ITS CONTRIBUTORS
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#pragma once

#include "Weak.h"
#include <wtf/HashMap.h>

namespace JSC {

// A HashMap with Weak<JSCell> values, which automatically removes values once they're garbage collected.

class WeakGCMapBase {
public:
    virtual ~WeakGCMapBase() { }
    virtual void pruneStaleEntries() = 0;
};

template<typename KeyArg, typename ValueArg, typename HashArg = typename DefaultHash<KeyArg>::Hash,
    typename KeyTraitsArg = HashTraits<KeyArg>>
class WeakGCMap final : public WeakGCMapBase {
    WTF_MAKE_FAST_ALLOCATED;
    typedef Weak<ValueArg> ValueType;
    typedef HashMap<KeyArg, ValueType, HashArg, KeyTraitsArg> HashMapType;

public:
    typedef typename HashMapType::KeyType KeyType;
    typedef typename HashMapType::AddResult AddResult;
    typedef typename HashMapType::iterator iterator;
    typedef typename HashMapType::const_iterator const_iterator;

    explicit WeakGCMap(VM&);
    ~WeakGCMap() final;

    ValueArg* get(const KeyType& key) const
    {
        return m_map.get(key);
    }

    AddResult set(const KeyType& key, ValueType value)
    {
        return m_map.set(key, WTFMove(value));
    }

    bool remove(const KeyType& key)
    {
        return m_map.remove(key);
    }

    void clear()
    {
        m_map.clear();
    }

    bool isEmpty() const
    {
        const_iterator it = m_map.begin();
        const_iterator end = m_map.end();
        while (it != end) {
            if (it->value)
                return true;
        }
        return false;
    }

    inline iterator find(const KeyType& key);

    inline const_iterator find(const KeyType& key) const;

    inline bool contains(const KeyType& key) const;

    void pruneStaleEntries() final;

private:
    HashMapType m_map;
    VM& m_vm;
};

} // namespace JSC