226 lines
7.8 KiB
C++
226 lines
7.8 KiB
C++
/*
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* Copyright (C) 2013-2017 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <wtf/Vector.h>
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namespace WebCore {
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WEBCORE_EXPORT void reportExtraMemoryAllocatedForCollectionIndexCache(size_t);
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template <class Collection, class Iterator>
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class CollectionIndexCache {
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public:
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CollectionIndexCache();
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typedef typename std::iterator_traits<Iterator>::value_type NodeType;
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unsigned nodeCount(const Collection&);
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NodeType* nodeAt(const Collection&, unsigned index);
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bool hasValidCache() const { return m_current || m_nodeCountValid || m_listValid; }
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void invalidate();
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size_t memoryCost()
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{
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// memoryCost() may be invoked concurrently from a GC thread, and we need to be careful
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// about what data we access here and how. Accessing m_cachedList.capacity() is safe
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// because it doesn't involve any pointer chasing.
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return m_cachedList.capacity() * sizeof(NodeType*);
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}
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private:
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unsigned computeNodeCountUpdatingListCache(const Collection&);
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NodeType* traverseBackwardTo(const Collection&, unsigned);
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NodeType* traverseForwardTo(const Collection&, unsigned);
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Iterator m_current { };
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unsigned m_currentIndex { 0 };
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unsigned m_nodeCount { 0 };
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Vector<NodeType*> m_cachedList;
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bool m_nodeCountValid : 1;
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bool m_listValid : 1;
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};
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template<class Collection, class Iterator> CollectionIndexCache<Collection, Iterator>::CollectionIndexCache()
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: m_nodeCountValid(false)
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, m_listValid(false)
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{
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}
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template <class Collection, class Iterator>
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inline unsigned CollectionIndexCache<Collection, Iterator>::nodeCount(const Collection& collection)
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{
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if (!m_nodeCountValid) {
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if (!hasValidCache())
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collection.willValidateIndexCache();
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m_nodeCount = computeNodeCountUpdatingListCache(collection);
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m_nodeCountValid = true;
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}
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return m_nodeCount;
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}
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template <class Collection, class Iterator>
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unsigned CollectionIndexCache<Collection, Iterator>::computeNodeCountUpdatingListCache(const Collection& collection)
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{
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auto current = collection.collectionBegin();
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if (!current)
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return 0;
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unsigned oldCapacity = m_cachedList.capacity();
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while (current) {
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m_cachedList.append(&*current);
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unsigned traversed;
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collection.collectionTraverseForward(current, 1, traversed);
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ASSERT(traversed == (current ? 1 : 0));
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}
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m_listValid = true;
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if (unsigned capacityDifference = m_cachedList.capacity() - oldCapacity)
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reportExtraMemoryAllocatedForCollectionIndexCache(capacityDifference * sizeof(NodeType*));
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return m_cachedList.size();
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}
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template <class Collection, class Iterator>
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inline typename CollectionIndexCache<Collection, Iterator>::NodeType* CollectionIndexCache<Collection, Iterator>::traverseBackwardTo(const Collection& collection, unsigned index)
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{
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ASSERT(m_current);
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ASSERT(index < m_currentIndex);
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bool firstIsCloser = index < m_currentIndex - index;
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if (firstIsCloser || !collection.collectionCanTraverseBackward()) {
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m_current = collection.collectionBegin();
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m_currentIndex = 0;
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if (index)
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collection.collectionTraverseForward(m_current, index, m_currentIndex);
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ASSERT(m_current);
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return &*m_current;
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}
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collection.collectionTraverseBackward(m_current, m_currentIndex - index);
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m_currentIndex = index;
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ASSERT(m_current);
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return &*m_current;
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}
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template <class Collection, class Iterator>
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inline typename CollectionIndexCache<Collection, Iterator>::NodeType* CollectionIndexCache<Collection, Iterator>::traverseForwardTo(const Collection& collection, unsigned index)
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{
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ASSERT(m_current);
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ASSERT(index > m_currentIndex);
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ASSERT(!m_nodeCountValid || index < m_nodeCount);
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bool lastIsCloser = m_nodeCountValid && m_nodeCount - index < index - m_currentIndex;
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if (lastIsCloser && collection.collectionCanTraverseBackward()) {
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ASSERT(hasValidCache());
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m_current = collection.collectionLast();
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if (index < m_nodeCount - 1)
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collection.collectionTraverseBackward(m_current, m_nodeCount - index - 1);
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m_currentIndex = index;
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ASSERT(m_current);
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return &*m_current;
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}
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if (!hasValidCache())
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collection.willValidateIndexCache();
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unsigned traversedCount;
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collection.collectionTraverseForward(m_current, index - m_currentIndex, traversedCount);
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m_currentIndex = m_currentIndex + traversedCount;
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if (!m_current) {
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ASSERT(m_currentIndex < index);
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// Failed to find the index but at least we now know the size.
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m_nodeCount = m_currentIndex + 1;
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m_nodeCountValid = true;
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return nullptr;
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}
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ASSERT(hasValidCache());
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return &*m_current;
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}
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template <class Collection, class Iterator>
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inline typename CollectionIndexCache<Collection, Iterator>::NodeType* CollectionIndexCache<Collection, Iterator>::nodeAt(const Collection& collection, unsigned index)
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{
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if (m_nodeCountValid && index >= m_nodeCount)
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return nullptr;
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if (m_listValid)
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return m_cachedList[index];
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if (m_current) {
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if (index > m_currentIndex)
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return traverseForwardTo(collection, index);
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if (index < m_currentIndex)
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return traverseBackwardTo(collection, index);
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return &*m_current;
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}
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bool lastIsCloser = m_nodeCountValid && m_nodeCount - index < index;
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if (lastIsCloser && collection.collectionCanTraverseBackward()) {
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ASSERT(hasValidCache());
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m_current = collection.collectionLast();
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if (index < m_nodeCount - 1)
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collection.collectionTraverseBackward(m_current, m_nodeCount - index - 1);
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m_currentIndex = index;
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ASSERT(m_current);
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return &*m_current;
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}
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if (!hasValidCache())
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collection.willValidateIndexCache();
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m_current = collection.collectionBegin();
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m_currentIndex = 0;
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bool startIsEnd = !m_current;
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if (index && m_current) {
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collection.collectionTraverseForward(m_current, index, m_currentIndex);
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ASSERT(m_current || m_currentIndex < index);
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}
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if (!m_current) {
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// Failed to find the index but at least we now know the size.
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m_nodeCount = startIsEnd ? 0 : m_currentIndex + 1;
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m_nodeCountValid = true;
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return nullptr;
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}
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ASSERT(hasValidCache());
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return &*m_current;
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}
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template <class Collection, class Iterator>
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void CollectionIndexCache<Collection, Iterator>::invalidate()
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{
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m_current = { };
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m_nodeCountValid = false;
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m_listValid = false;
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m_cachedList.shrink(0);
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}
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}
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