Source/JavaScriptCore/heap/HandleBlock.h

/*
 * Copyright (C) 2013-2019 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 INC. AND ITS CONTRIBUTORS ``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 INC. OR ITS 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
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <wtf/DoublyLinkedList.h>

namespace JSC {

class HandleSet;
class HandleNode;

class HandleBlock : public DoublyLinkedListNode<HandleBlock> {
    friend class WTF::DoublyLinkedListNode<HandleBlock>;
public:
    static HandleBlock* create(HandleSet*);
    static void destroy(HandleBlock*);
    static HandleBlock* blockFor(HandleNode*);

    static constexpr size_t blockSize = 4 * KB;

    HandleSet* handleSet();

    HandleNode* nodes();
    HandleNode* nodeAtIndex(unsigned);
    unsigned nodeCapacity();

private:
    HandleBlock(HandleSet*);

    char* payload();
    char* payloadEnd();

    static constexpr size_t s_blockMask = ~(blockSize - 1);

    HandleBlock* m_prev;
    HandleBlock* m_next;
    HandleSet* m_handleSet;
};

inline HandleBlock* HandleBlock::blockFor(HandleNode* node)
{
    return reinterpret_cast<HandleBlock*>(reinterpret_cast<size_t>(node) & s_blockMask);
}

inline HandleSet* HandleBlock::handleSet()
{
    return m_handleSet;
}

} // namespace JSC