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      1 /*
      2  * Copyright (C) 2012, 2013 Apple Inc. All Rights Reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  *
     25  */
     26 
     27 #include "config.h"
     28 #include "core/dom/ElementDataCache.h"
     29 
     30 #include "core/dom/ElementData.h"
     31 
     32 namespace blink {
     33 
     34 DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(ElementDataCache)
     35 
     36 inline unsigned attributeHash(const Vector<Attribute>& attributes)
     37 {
     38     return StringHasher::hashMemory(attributes.data(), attributes.size() * sizeof(Attribute));
     39 }
     40 
     41 inline bool hasSameAttributes(const Vector<Attribute>& attributes, ShareableElementData& elementData)
     42 {
     43     if (attributes.size() != elementData.attributes().size())
     44         return false;
     45     return !memcmp(attributes.data(), elementData.m_attributeArray, attributes.size() * sizeof(Attribute));
     46 }
     47 
     48 PassRefPtrWillBeRawPtr<ShareableElementData> ElementDataCache::cachedShareableElementDataWithAttributes(const Vector<Attribute>& attributes)
     49 {
     50     ASSERT(!attributes.isEmpty());
     51 
     52     ShareableElementDataCache::ValueType* it = m_shareableElementDataCache.add(attributeHash(attributes), nullptr).storedValue;
     53 
     54     // FIXME: This prevents sharing when there's a hash collision.
     55     if (it->value && !hasSameAttributes(attributes, *it->value))
     56         return ShareableElementData::createWithAttributes(attributes);
     57 
     58     if (!it->value)
     59         it->value = ShareableElementData::createWithAttributes(attributes);
     60 
     61     return it->value.get();
     62 }
     63 
     64 ElementDataCache::ElementDataCache()
     65 {
     66 }
     67 
     68 void ElementDataCache::trace(Visitor* visitor)
     69 {
     70 #if ENABLE(OILPAN)
     71     visitor->trace(m_shareableElementDataCache);
     72 #endif
     73 }
     74 
     75 }
     76