| /* |
| * Copyright (C) 2013 Apple Inc. All rights reserved. |
| * Copyright (C) 2014 Samsung Electronics. 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 CollectionIndexCache_h |
| #define CollectionIndexCache_h |
| |
| #include "core/dom/Element.h" |
| |
| namespace WebCore { |
| |
| template <typename Collection, typename NodeType> |
| class CollectionIndexCache { |
| DISALLOW_ALLOCATION(); |
| public: |
| CollectionIndexCache(); |
| |
| bool isEmpty(const Collection& collection) |
| { |
| if (isCachedNodeCountValid()) |
| return !cachedNodeCount(); |
| if (cachedNode()) |
| return false; |
| return !nodeAt(collection, 0); |
| } |
| bool hasExactlyOneNode(const Collection& collection) |
| { |
| if (isCachedNodeCountValid()) |
| return cachedNodeCount() == 1; |
| if (cachedNode()) |
| return !cachedNodeIndex() && !nodeAt(collection, 1); |
| return nodeAt(collection, 0) && !nodeAt(collection, 1); |
| } |
| |
| unsigned nodeCount(const Collection&); |
| NodeType* nodeAt(const Collection&, unsigned index); |
| |
| void invalidate(); |
| |
| void trace(Visitor* visitor) |
| { |
| visitor->trace(m_currentNode); |
| } |
| |
| private: |
| NodeType* nodeBeforeCachedNode(const Collection&, unsigned index); |
| NodeType* nodeAfterCachedNode(const Collection&, unsigned index); |
| |
| ALWAYS_INLINE NodeType* cachedNode() const { return m_currentNode; } |
| ALWAYS_INLINE unsigned cachedNodeIndex() const { ASSERT(cachedNode()); return m_cachedNodeIndex; } |
| ALWAYS_INLINE void setCachedNode(NodeType* node, unsigned index) |
| { |
| ASSERT(node); |
| m_currentNode = node; |
| m_cachedNodeIndex = index; |
| } |
| |
| ALWAYS_INLINE bool isCachedNodeCountValid() const { return m_isLengthCacheValid; } |
| ALWAYS_INLINE unsigned cachedNodeCount() const { return m_cachedNodeCount; } |
| ALWAYS_INLINE void setCachedNodeCount(unsigned length) |
| { |
| m_cachedNodeCount = length; |
| m_isLengthCacheValid = true; |
| } |
| |
| RawPtrWillBeMember<NodeType> m_currentNode; |
| unsigned m_cachedNodeCount; |
| unsigned m_cachedNodeIndex; |
| unsigned m_isLengthCacheValid : 1; |
| }; |
| |
| template <typename Collection, typename NodeType> |
| CollectionIndexCache<Collection, NodeType>::CollectionIndexCache() |
| : m_currentNode(nullptr) |
| , m_cachedNodeCount(0) |
| , m_cachedNodeIndex(0) |
| , m_isLengthCacheValid(false) |
| { |
| } |
| |
| template <typename Collection, typename NodeType> |
| void CollectionIndexCache<Collection, NodeType>::invalidate() |
| { |
| m_currentNode = nullptr; |
| m_isLengthCacheValid = false; |
| } |
| |
| template <typename Collection, typename NodeType> |
| inline unsigned CollectionIndexCache<Collection, NodeType>::nodeCount(const Collection& collection) |
| { |
| if (isCachedNodeCountValid()) |
| return cachedNodeCount(); |
| |
| nodeAt(collection, UINT_MAX); |
| ASSERT(isCachedNodeCountValid()); |
| |
| return cachedNodeCount(); |
| } |
| |
| template <typename Collection, typename NodeType> |
| inline NodeType* CollectionIndexCache<Collection, NodeType>::nodeAt(const Collection& collection, unsigned index) |
| { |
| if (isCachedNodeCountValid() && index >= cachedNodeCount()) |
| return 0; |
| |
| if (cachedNode()) { |
| if (index > cachedNodeIndex()) |
| return nodeAfterCachedNode(collection, index); |
| if (index < cachedNodeIndex()) |
| return nodeBeforeCachedNode(collection, index); |
| return cachedNode(); |
| } |
| |
| // No valid cache yet, let's find the first matching element. |
| ASSERT(!isCachedNodeCountValid()); |
| NodeType* firstNode = collection.traverseToFirstElement(); |
| if (!firstNode) { |
| // The collection is empty. |
| setCachedNodeCount(0); |
| return 0; |
| } |
| setCachedNode(firstNode, 0); |
| return index ? nodeAfterCachedNode(collection, index) : firstNode; |
| } |
| |
| template <typename Collection, typename NodeType> |
| inline NodeType* CollectionIndexCache<Collection, NodeType>::nodeBeforeCachedNode(const Collection& collection, unsigned index) |
| { |
| ASSERT(cachedNode()); // Cache should be valid. |
| unsigned currentIndex = cachedNodeIndex(); |
| ASSERT(currentIndex > index); |
| |
| // Determine if we should traverse from the beginning of the collection instead of the cached node. |
| bool firstIsCloser = index < currentIndex - index; |
| if (firstIsCloser || !collection.canTraverseBackward()) { |
| NodeType* firstNode = collection.traverseToFirstElement(); |
| ASSERT(firstNode); |
| setCachedNode(firstNode, 0); |
| return index ? nodeAfterCachedNode(collection, index) : firstNode; |
| } |
| |
| // Backward traversal from the cached node to the requested index. |
| ASSERT(collection.canTraverseBackward()); |
| NodeType* currentNode = collection.traverseBackwardToOffset(index, *cachedNode(), currentIndex); |
| ASSERT(currentNode); |
| setCachedNode(currentNode, currentIndex); |
| return currentNode; |
| } |
| |
| template <typename Collection, typename NodeType> |
| inline NodeType* CollectionIndexCache<Collection, NodeType>::nodeAfterCachedNode(const Collection& collection, unsigned index) |
| { |
| ASSERT(cachedNode()); // Cache should be valid. |
| unsigned currentIndex = cachedNodeIndex(); |
| ASSERT(currentIndex < index); |
| |
| // Determine if we should traverse from the end of the collection instead of the cached node. |
| bool lastIsCloser = isCachedNodeCountValid() && cachedNodeCount() - index < index - currentIndex; |
| if (lastIsCloser && collection.canTraverseBackward()) { |
| NodeType* lastItem = collection.traverseToLastElement(); |
| ASSERT(lastItem); |
| setCachedNode(lastItem, cachedNodeCount() - 1); |
| if (index < cachedNodeCount() - 1) |
| return nodeBeforeCachedNode(collection, index); |
| return lastItem; |
| } |
| |
| // Forward traversal from the cached node to the requested index. |
| NodeType* currentNode = collection.traverseForwardToOffset(index, *cachedNode(), currentIndex); |
| if (!currentNode) { |
| // Did not find the node. On plus side, we now know the length. |
| setCachedNodeCount(currentIndex + 1); |
| return 0; |
| } |
| setCachedNode(currentNode, currentIndex); |
| return currentNode; |
| } |
| |
| } // namespace WebCore |
| |
| #endif // CollectionIndexCache_h |