73 lines
2.2 KiB
C++
73 lines
2.2 KiB
C++
/*
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open source routing machine
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Copyright (C) Dennis Luxen, others 2010
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU AFFERO General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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or see http://www.gnu.org/licenses/agpl.txt.
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*/
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#ifndef LRUCACHE_H
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#define LRUCACHE_H
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#include <list>
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#include <boost/unordered_map.hpp>
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template<typename KeyT, typename ValueT>
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class LRUCache {
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private:
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struct CacheEntry {
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CacheEntry(KeyT k, ValueT v) : key(k), value(v) {}
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KeyT key;
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ValueT value;
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};
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unsigned capacity;
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std::list<CacheEntry> itemsInCache;
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boost::unordered_map<KeyT, typename std::list<CacheEntry>::iterator > positionMap;
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public:
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LRUCache(unsigned c) : capacity(c) {}
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bool Holds(KeyT key) {
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if(positionMap.find(key) != positionMap.end()) {
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return true;
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}
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return false;
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}
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void Insert(const KeyT key, ValueT &value) {
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itemsInCache.push_front(CacheEntry(key, value));
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positionMap.insert(std::make_pair(key, itemsInCache.begin()));
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if(itemsInCache.size() > capacity) {
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positionMap.erase(itemsInCache.back().key);
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itemsInCache.pop_back();
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}
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}
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bool Fetch(const KeyT key, ValueT& result) {
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if(Holds(key)) {
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CacheEntry e = *(positionMap.find(key)->second);
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result = e.value;
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//move to front
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itemsInCache.splice(positionMap.find(key)->second, itemsInCache, itemsInCache.begin());
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positionMap.find(key)->second = itemsInCache.begin();
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return true;
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}
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return false;
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}
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unsigned Size() const {
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return itemsInCache.size();
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}
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};
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#endif //LRUCACHE_H
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