1 /* 2 * Copyright (C) 2010 Apple Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' 14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS 17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 23 * THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #ifndef AtomicStringKeyedMRUCache_h 27 #define AtomicStringKeyedMRUCache_h 28 29 #include <wtf/text/AtomicString.h> 30 31 namespace WebCore { 32 33 template<typename T, size_t capacity = 4> 34 class AtomicStringKeyedMRUCache { 35 public: get(const AtomicString & key)36 T get(const AtomicString& key) 37 { 38 if (key.isNull()) { 39 DEFINE_STATIC_LOCAL(T, valueForNull, (createValueForNullKey())); 40 return valueForNull; 41 } 42 43 for (size_t i = 0; i < m_cache.size(); ++i) { 44 if (m_cache[i].first == key) { 45 size_t foundIndex = i; 46 if (foundIndex + 1 < m_cache.size()) { 47 Entry entry = m_cache[foundIndex]; 48 m_cache.remove(foundIndex); 49 foundIndex = m_cache.size(); 50 m_cache.append(entry); 51 } 52 return m_cache[foundIndex].second; 53 } 54 } 55 if (m_cache.size() == capacity) 56 m_cache.remove(0); 57 58 m_cache.append(std::make_pair(key, createValueForKey(key))); 59 return m_cache.last().second; 60 } 61 62 private: 63 T createValueForNullKey(); 64 T createValueForKey(const AtomicString&); 65 66 typedef pair<AtomicString, T> Entry; 67 typedef Vector<Entry, capacity> Cache; 68 Cache m_cache; 69 }; 70 71 } 72 73 #endif // AtomicStringKeyedMRUCache_h 74