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

/*
 * Copyright (C) 2013 Google 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:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
 * OWNER 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 OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "core/dom/ElementData.h"

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

namespace blink {

struct SameSizeAsElementData
    : public GarbageCollectedFinalized<SameSizeAsElementData> {
  unsigned bitfield;
  Member<void*> willbe_member;
  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()
    : is_unique_(true),
      array_size_(0),
      presentation_attribute_style_is_dirty_(false),
      style_attribute_is_dirty_(false),
      animated_svg_attributes_are_dirty_(false) {}

ElementData::ElementData(unsigned array_size)
    : is_unique_(false),
      array_size_(array_size),
      presentation_attribute_style_is_dirty_(false),
      style_attribute_is_dirty_(false),
      animated_svg_attributes_are_dirty_(false) {}

ElementData::ElementData(const ElementData& other, bool is_unique)
    : is_unique_(is_unique),
      array_size_(is_unique ? 0 : other.Attributes().size()),
      presentation_attribute_style_is_dirty_(
          other.presentation_attribute_style_is_dirty_),
      style_attribute_is_dirty_(other.style_attribute_is_dirty_),
      animated_svg_attributes_are_dirty_(
          other.animated_svg_attributes_are_dirty_),
      class_names_(other.class_names_),
      id_for_style_resolution_(other.id_for_style_resolution_) {
  // 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 (is_unique_)
    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 = Attributes();
  if (!other)
    return attributes.IsEmpty();

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

  for (const Attribute& attribute : attributes) {
    const Attribute* other_attr = other_attributes.Find(attribute.GetName());
    if (!other_attr || attribute.Value() != other_attr->Value())
      return false;
  }
  return true;
}

void ElementData::Trace(blink::Visitor* visitor) {
  if (is_unique_)
    ToUniqueElementData(this)->TraceAfterDispatch(visitor);
  else
    ToShareableElementData(this)->TraceAfterDispatch(visitor);
}

void ElementData::TraceAfterDispatch(blink::Visitor* visitor) {
  visitor->Trace(inline_style_);
}

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

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

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

  if (other.inline_style_) {
    inline_style_ = other.inline_style_->ImmutableCopyIfNeeded();
  }

  for (unsigned i = 0; i < array_size_; ++i)
    new (&attribute_array_[i]) Attribute(other.attribute_vector_.at(i));
}

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

UniqueElementData::UniqueElementData() = default;

UniqueElementData::UniqueElementData(const UniqueElementData& other)
    : ElementData(other, true),
      presentation_attribute_style_(other.presentation_attribute_style_),
      attribute_vector_(other.attribute_vector_) {
  inline_style_ =
      other.inline_style_ ? other.inline_style_->MutableCopy() : nullptr;
}

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

  unsigned length = other.Attributes().size();
  attribute_vector_.ReserveCapacity(length);
  for (unsigned i = 0; i < length; ++i)
    attribute_vector_.UncheckedAppend(other.attribute_array_[i]);
}

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

ShareableElementData* UniqueElementData::MakeShareableCopy() const {
  void* slot = ThreadHeap::Allocate<ElementData>(
      SizeForShareableElementDataWithAttributeCount(attribute_vector_.size()));
  return new (slot) ShareableElementData(*this);
}

void UniqueElementData::TraceAfterDispatch(blink::Visitor* visitor) {
  visitor->Trace(presentation_attribute_style_);
  ElementData::TraceAfterDispatch(visitor);
}

}  // namespace blink