DocumentSharedObjectPool.cpp   [plain text]

/*
 * Copyright (C) 2012, 2013 Apple Inc. All Rights Reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE 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 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
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#include "config.h"
#include "DocumentSharedObjectPool.h"

#include "Element.h"

namespace WebCore {

inline unsigned attributeHash(const Vector<Attribute>& attributes)
{
    return StringHasher::hashMemory(attributes.data(), attributes.size() * sizeof(Attribute));
}

inline bool hasSameAttributes(const Vector<Attribute>& attributes, ShareableElementData& elementData)
{
    if (attributes.size() != elementData.length())
        return false;
    return !memcmp(attributes.data(), elementData.m_attributeArray, attributes.size() * sizeof(Attribute));
}

Ref<ShareableElementData> DocumentSharedObjectPool::cachedShareableElementDataWithAttributes(const Vector<Attribute>& attributes)
{
    ASSERT(!attributes.isEmpty());

    auto& cachedData = m_shareableElementDataCache.add(attributeHash(attributes), nullptr).iterator->value;

    // FIXME: This prevents sharing when there's a hash collision.
    if (cachedData && !hasSameAttributes(attributes, *cachedData))
        return ShareableElementData::createWithAttributes(attributes);

    if (!cachedData)
        cachedData = ShareableElementData::createWithAttributes(attributes);

    return *cachedData;
}

}