third_party/WebKit/Source/core/dom/ElementData.cpp

/*
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 * modification, are permitted provided that the following conditions are
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 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
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#include "core/dom/ElementData.h"

#include "core/css/StylePropertySet.h"
#include "core/dom/QualifiedName.h"
#include "wtf/Vector.h"

namespace blink {

struct SameSizeAsElementData
    : public GarbageCollectedFinalized<SameSizeAsElementData> {
  unsigned bitfield;
  Member<void*> willbeMember;
  void* pointers[2];
};

static_assert(sizeof(ElementData) == sizeof(SameSizeAsElementData),
              "ElementData should stay small");

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

ElementData::ElementData()
    : m_isUnique(true),
      m_arraySize(0),
      m_presentationAttributeStyleIsDirty(false),
      m_styleAttributeIsDirty(false),
      m_animatedSVGAttributesAreDirty(false) {}

ElementData::ElementData(unsigned arraySize)
    : m_isUnique(false),
      m_arraySize(arraySize),
      m_presentationAttributeStyleIsDirty(false),
      m_styleAttributeIsDirty(false),
      m_animatedSVGAttributesAreDirty(false) {}

ElementData::ElementData(const ElementData& other, bool isUnique)
    : m_isUnique(isUnique),
      m_arraySize(isUnique ? 0 : other.attributes().size()),
      m_presentationAttributeStyleIsDirty(
          other.m_presentationAttributeStyleIsDirty),
      m_styleAttributeIsDirty(other.m_styleAttributeIsDirty),
      m_animatedSVGAttributesAreDirty(other.m_animatedSVGAttributesAreDirty),
      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.
}

void ElementData::finalizeGarbageCollectedObject() {
  if (m_isUnique)
    toUniqueElementData(this)->~UniqueElementData();
  else
    toShareableElementData(this)->~ShareableElementData();
}

UniqueElementData* ElementData::makeUniqueCopy() const {
  if (isUnique())
    return new UniqueElementData(toUniqueElementData(*this));
  return new UniqueElementData(toShareableElementData(*this));
}

bool ElementData::isEquivalent(const ElementData* other) const {
  AttributeCollection attributes = this->attributes();
  if (!other)
    return attributes.isEmpty();

  AttributeCollection otherAttributes = other->attributes();
  if (attributes.size() != otherAttributes.size())
    return false;

  for (const Attribute& attribute : attributes) {
    const Attribute* otherAttr = otherAttributes.find(attribute.name());
    if (!otherAttr || attribute.value() != otherAttr->value())
      return false;
  }
  return true;
}

DEFINE_TRACE(ElementData) {
  if (m_isUnique)
    toUniqueElementData(this)->traceAfterDispatch(visitor);
  else
    toShareableElementData(this)->traceAfterDispatch(visitor);
}

DEFINE_TRACE_AFTER_DISPATCH(ElementData) {
  visitor->trace(m_inlineStyle);
}

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

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

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

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

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

ShareableElementData* ShareableElementData::createWithAttributes(
    const Vector<Attribute>& attributes) {
  void* slot = ThreadHeap::allocate<ElementData>(
      sizeForShareableElementDataWithAttributeCount(attributes.size()));
  return new (slot) ShareableElementData(attributes);
}

UniqueElementData::UniqueElementData() {}

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

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

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

UniqueElementData* UniqueElementData::create() {
  return new UniqueElementData;
}

ShareableElementData* UniqueElementData::makeShareableCopy() const {
  void* slot = ThreadHeap::allocate<ElementData>(
      sizeForShareableElementDataWithAttributeCount(m_attributeVector.size()));
  return new (slot) ShareableElementData(*this);
}

DEFINE_TRACE_AFTER_DISPATCH(UniqueElementData) {
  visitor->trace(m_presentationAttributeStyle);
  ElementData::traceAfterDispatch(visitor);
}

}  // namespace blink