text: /*
   * Copyright (C) 2011 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.
   */
  
  #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_DOM_CHILD_LIST_MUTATION_SCOPE_H_
  #define THIRD_PARTY_BLINK_RENDERER_CORE_DOM_CHILD_LIST_MUTATION_SCOPE_H_
  
  #include "base/macros.h"
  #include "third_party/blink/renderer/core/dom/document.h"
  #include "third_party/blink/renderer/core/dom/mutation_observer.h"
  #include "third_party/blink/renderer/core/dom/node.h"
  #include "third_party/blink/renderer/platform/heap/handle.h"
  
  namespace blink {
  
  class MutationObserverInterestGroup;
  
  // ChildListMutationAccumulator is not meant to be used directly;
  // ChildListMutationScope is the public interface.
  //
  // One ChildListMutationAccumulator for a given Node is shared between all the
  // active ChildListMutationScopes for that Node. Once the last
  // ChildListMutationScope is destructed the accumulator enqueues a mutation
  // record for the recorded mutations and the accumulator can be garbage
  // collected.
  class ChildListMutationAccumulator final
      : public GarbageCollected<ChildListMutationAccumulator> {
   public:
    static ChildListMutationAccumulator* GetOrCreate(Node&);
  
    void ChildAdded(Node*);
    void WillRemoveChild(Node*);
  
    bool HasObservers() const { return observers_; }
  
    // Register and unregister mutation scopes that are using this mutation
    // accumulator.
    void EnterMutationScope() { mutation_scopes_++; }
    void LeaveMutationScope();
  
    void Trace(blink::Visitor*);
  
   private:
    ChildListMutationAccumulator(Node*, MutationObserverInterestGroup*);
  
    void EnqueueMutationRecord();
    bool IsEmpty();
    bool IsAddedNodeInOrder(Node*);
    bool IsRemovedNodeInOrder(Node*);
  
    Member<Node> target_;
  
    HeapVector<Member<Node>> removed_nodes_;
    HeapVector<Member<Node>> added_nodes_;
    Member<Node> previous_sibling_;
    Member<Node> next_sibling_;
    Member<Node> last_added_;
  
    Member<MutationObserverInterestGroup> observers_;
  
    unsigned mutation_scopes_;
  };
  
  class ChildListMutationScope final {
    STACK_ALLOCATED();
  
   public:
    explicit ChildListMutationScope(Node& target) {
      if (target.GetDocument().HasMutationObserversOfType(
              MutationObserver::kChildList)) {
        accumulator_ = ChildListMutationAccumulator::GetOrCreate(target);
        // Register another user of the accumulator.
        accumulator_->EnterMutationScope();
      }
    }
  
    ~ChildListMutationScope() {
      if (accumulator_) {
        // Unregister a user of the accumulator. If this is the last user
        // the accumulator will enqueue a mutation record for the mutations.
        accumulator_->LeaveMutationScope();
      }
    }
  
    void ChildAdded(Node& child) {
      if (accumulator_ && accumulator_->HasObservers())
        accumulator_->ChildAdded(&child);
    }
  
    void WillRemoveChild(Node& child) {
      if (accumulator_ && accumulator_->HasObservers())
        accumulator_->WillRemoveChild(&child);
    }
  
   private:
    Member<ChildListMutationAccumulator> accumulator_;
    DISALLOW_COPY_AND_ASSIGN(ChildListMutationScope);
  };
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_DOM_CHILD_LIST_MUTATION_SCOPE_H_
  