Source/WebCore/dom/ElementData.cpp

/*
 * Copyright (C) 2013, 2014 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
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 *    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. ``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
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#include "config.h"
#include "ElementData.h"

#include "Attr.h"
#include "HTMLNames.h"
#include "StyleProperties.h"
#include "XMLNames.h"

namespace WebCore {

void ElementData::destroy()
{
    if (is<UniqueElementData>(*this))
        delete downcast<UniqueElementData>(this);
    else
        delete downcast<ShareableElementData>(this);
}

ElementData::ElementData()
    : m_arraySizeAndFlags(s_flagIsUnique)
{
}

ElementData::ElementData(unsigned arraySize)
    : m_arraySizeAndFlags(arraySize << s_flagCount)
{
}

struct SameSizeAsElementData : public RefCounted<SameSizeAsElementData> {
    unsigned bitfield;
    void* refPtrs[3];
};

COMPILE_ASSERT(sizeof(ElementData) == sizeof(SameSizeAsElementData), element_attribute_data_should_stay_small);

static size_t sizeForShareableElementDataWithAttributeCount(unsigned count)
{
    return sizeof(ShareableElementData) + sizeof(Attribute) * count;
}

Ref<ShareableElementData> ShareableElementData::createWithAttributes(const Vector<Attribute>& attributes)
{
    void* slot = WTF::fastMalloc(sizeForShareableElementDataWithAttributeCount(attributes.size()));
    return adoptRef(*new (NotNull, slot) ShareableElementData(attributes));
}

Ref<UniqueElementData> UniqueElementData::create()
{
    return adoptRef(*new UniqueElementData);
}

ShareableElementData::ShareableElementData(const Vector<Attribute>& attributes)
    : ElementData(attributes.size())
{
    unsigned attributeArraySize = arraySize();
    for (unsigned i = 0; i < attributeArraySize; ++i)
        new (NotNull, &m_attributeArray[i]) Attribute(attributes[i]);
}

ShareableElementData::~ShareableElementData()
{
    unsigned attributeArraySize = arraySize();
    for (unsigned i = 0; i < attributeArraySize; ++i)
        m_attributeArray[i].~Attribute();
}

ShareableElementData::ShareableElementData(const UniqueElementData& other)
    : ElementData(other, false)
{
    ASSERT(!other.m_presentationAttributeStyle);

    if (other.m_inlineStyle) {
        ASSERT(!other.m_inlineStyle->hasCSSOMWrapper());
        m_inlineStyle = other.m_inlineStyle->immutableCopyIfNeeded();
    }

    unsigned attributeArraySize = arraySize();
    for (unsigned i = 0; i < attributeArraySize; ++i)
        new (NotNull, &m_attributeArray[i]) Attribute(other.m_attributeVector.at(i));
}

inline uint32_t ElementData::arraySizeAndFlagsFromOther(const ElementData& other, bool isUnique)
{
    if (isUnique) {
        // Set isUnique and ignore arraySize.
        return (other.m_arraySizeAndFlags | s_flagIsUnique) & s_flagsMask;
    }
    // Clear isUnique and set arraySize.
    return (other.m_arraySizeAndFlags & (s_flagsMask & ~s_flagIsUnique)) | other.length() << s_flagCount;
}

ElementData::ElementData(const ElementData& other, bool isUnique)
    : m_arraySizeAndFlags(ElementData::arraySizeAndFlagsFromOther(other, isUnique))
    , m_classNames(other.m_classNames)
    , m_idForStyleResolution(other.m_idForStyleResolution)
{
    // NOTE: The inline style is copied by the subclass copy constructor since we don't know what to do with it here.
}

UniqueElementData::UniqueElementData()
{
}

UniqueElementData::UniqueElementData(const UniqueElementData& other)
    : ElementData(other, true)
    , m_presentationAttributeStyle(other.m_presentationAttributeStyle)
    , m_attributeVector(other.m_attributeVector)
{
    if (other.m_inlineStyle)
        m_inlineStyle = other.m_inlineStyle->mutableCopy();
}

UniqueElementData::UniqueElementData(const ShareableElementData& other)
    : ElementData(other, true)
{
    // An ShareableElementData should never have a mutable inline StyleProperties attached.
    ASSERT(!other.m_inlineStyle || !other.m_inlineStyle->isMutable());
    m_inlineStyle = other.m_inlineStyle;

    unsigned otherLength = other.length();
    m_attributeVector.reserveCapacity(otherLength);
    for (unsigned i = 0; i < otherLength; ++i)
        m_attributeVector.uncheckedAppend(other.m_attributeArray[i]);
}

Ref<UniqueElementData> ElementData::makeUniqueCopy() const
{
    if (isUnique())
        return adoptRef(*new UniqueElementData(static_cast<const UniqueElementData&>(*this)));
    return adoptRef(*new UniqueElementData(static_cast<const ShareableElementData&>(*this)));
}

Ref<ShareableElementData> UniqueElementData::makeShareableCopy() const
{
    void* slot = WTF::fastMalloc(sizeForShareableElementDataWithAttributeCount(m_attributeVector.size()));
    return adoptRef(*new (NotNull, slot) ShareableElementData(*this));
}

bool ElementData::isEquivalent(const ElementData* other) const
{
    if (!other)
        return isEmpty();

    if (length() != other->length())
        return false;

    for (const Attribute& attribute : attributesIterator()) {
        const Attribute* otherAttr = other->findAttributeByName(attribute.name());
        if (!otherAttr || attribute.value() != otherAttr->value())
            return false;
    }

    return true;
}

Attribute* UniqueElementData::findAttributeByName(const QualifiedName& name)
{
    for (auto& attribute : m_attributeVector) {
        if (attribute.name().matches(name))
            return &attribute;
    }
    return nullptr;
}

const Attribute* ElementData::findLanguageAttribute() const
{
    ASSERT(XMLNames::langAttr->localName() == HTMLNames::langAttr->localName());

    const Attribute* attributes = attributeBase();
    // Spec: xml:lang takes precedence over html:lang -- http://www.w3.org/TR/xhtml1/#C_7
    const Attribute* languageAttribute = nullptr;
    for (unsigned i = 0, count = length(); i < count; ++i) {
        const QualifiedName& name = attributes[i].name();
        if (name.localName() != HTMLNames::langAttr->localName())
            continue;
        if (name.namespaceURI() == XMLNames::langAttr->namespaceURI())
            return &attributes[i];
        if (name.namespaceURI() == HTMLNames::langAttr->namespaceURI())
            languageAttribute = &attributes[i];
    }
    return languageAttribute;
}

}