98 lines
3.1 KiB
C++
98 lines
3.1 KiB
C++
/*
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Copyright (c) 2013, Project OSRM, Dennis Luxen, others
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All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this list
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of conditions and the following disclaimer.
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Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or
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other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
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ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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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 <unordered_map>
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template <typename KeyT, typename ValueT> class LRUCache
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{
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private:
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struct CacheEntry
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{
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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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std::unordered_map<KeyT, typename std::list<CacheEntry>::iterator> positionMap;
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public:
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explicit LRUCache(unsigned c) : capacity(c) {}
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bool Holds(KeyT key)
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{
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if (positionMap.find(key) != positionMap.end())
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{
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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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{
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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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{
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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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void Insert(const KeyT key, ValueT value)
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{
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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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{
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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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{
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if (Holds(key))
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{
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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 { return itemsInCache.size(); }
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};
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#endif // LRUCACHE_H
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