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

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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#include "core/dom/ChildListMutationScope.h"

#include "core/dom/MutationObserverInterestGroup.h"
#include "core/dom/MutationRecord.h"
#include "core/dom/StaticNodeList.h"
#include "wtf/HashMap.h"
#include "wtf/StdLibExtras.h"

namespace blink {

// The accumulator map is used to make sure that there is only one mutation
// accumulator for a given node even if there are multiple ChildListMutationScopes
// on the stack. The map is always empty when there are no ChildListMutationScopes
// on the stack.
typedef HeapHashMap<Member<Node>, Member<ChildListMutationAccumulator>> AccumulatorMap;

static AccumulatorMap& accumulatorMap()
{
    DEFINE_STATIC_LOCAL(AccumulatorMap, map, (new AccumulatorMap));
    return map;
}

ChildListMutationAccumulator::ChildListMutationAccumulator(Node* target, MutationObserverInterestGroup* observers)
    : m_target(target)
    , m_lastAdded(nullptr)
    , m_observers(observers)
    , m_mutationScopes(0)
{
}

void ChildListMutationAccumulator::leaveMutationScope()
{
    DCHECK_GT(m_mutationScopes, 0u);
    if (!--m_mutationScopes) {
        if (!isEmpty())
            enqueueMutationRecord();
        accumulatorMap().remove(m_target.get());
    }
}

ChildListMutationAccumulator* ChildListMutationAccumulator::getOrCreate(Node& target)
{
    AccumulatorMap::AddResult result = accumulatorMap().add(&target, nullptr);
    ChildListMutationAccumulator* accumulator;
    if (!result.isNewEntry) {
        accumulator = result.storedValue->value;
    } else {
        accumulator = new ChildListMutationAccumulator(&target, MutationObserverInterestGroup::createForChildListMutation(target));
        result.storedValue->value = accumulator;
    }
    return accumulator;
}

inline bool ChildListMutationAccumulator::isAddedNodeInOrder(Node* child)
{
    return isEmpty() || (m_lastAdded == child->previousSibling() && m_nextSibling == child->nextSibling());
}

void ChildListMutationAccumulator::childAdded(Node* child)
{
    DCHECK(hasObservers());

    if (!isAddedNodeInOrder(child))
        enqueueMutationRecord();

    if (isEmpty()) {
        m_previousSibling = child->previousSibling();
        m_nextSibling = child->nextSibling();
    }

    m_lastAdded = child;
    m_addedNodes.append(child);
}

inline bool ChildListMutationAccumulator::isRemovedNodeInOrder(Node* child)
{
    return isEmpty() || m_nextSibling == child;
}

void ChildListMutationAccumulator::willRemoveChild(Node* child)
{
    DCHECK(hasObservers());

    if (!m_addedNodes.isEmpty() || !isRemovedNodeInOrder(child))
        enqueueMutationRecord();

    if (isEmpty()) {
        m_previousSibling = child->previousSibling();
        m_nextSibling = child->nextSibling();
        m_lastAdded = child->previousSibling();
    } else {
        m_nextSibling = child->nextSibling();
    }

    m_removedNodes.append(child);
}

void ChildListMutationAccumulator::enqueueMutationRecord()
{
    DCHECK(hasObservers());
    DCHECK(!isEmpty());

    StaticNodeList* addedNodes = StaticNodeList::adopt(m_addedNodes);
    StaticNodeList* removedNodes = StaticNodeList::adopt(m_removedNodes);
    MutationRecord* record = MutationRecord::createChildList(m_target, addedNodes, removedNodes, m_previousSibling.release(), m_nextSibling.release());
    m_observers->enqueueMutationRecord(record);
    m_lastAdded = nullptr;
    DCHECK(isEmpty());
}

bool ChildListMutationAccumulator::isEmpty()
{
    bool result = m_removedNodes.isEmpty() && m_addedNodes.isEmpty();
#if DCHECK_IS_ON()
    if (result) {
        DCHECK(!m_previousSibling);
        DCHECK(!m_nextSibling);
        DCHECK(!m_lastAdded);
    }
#endif
    return result;
}

DEFINE_TRACE(ChildListMutationAccumulator)
{
    visitor->trace(m_target);
    visitor->trace(m_removedNodes);
    visitor->trace(m_addedNodes);
    visitor->trace(m_previousSibling);
    visitor->trace(m_nextSibling);
    visitor->trace(m_lastAdded);
    visitor->trace(m_observers);
}

} // namespace blink