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64 lines
1.2 KiB
64 lines
1.2 KiB
#ifndef LRU_CACHE_POLICY_HPP
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#define LRU_CACHE_POLICY_HPP
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#include <list>
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#include <unordered_map>
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#include "cache_policy.hpp"
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namespace caches
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{
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template <typename Key>
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class LRUCachePolicy : public ICachePolicy<Key>
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{
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public:
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using lru_iterator = typename std::list<Key>::const_iterator;
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LRUCachePolicy() = default;
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~LRUCachePolicy() = default;
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void Insert(const Key& key) override
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{
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lru_queue.emplace_front(key);
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key_finder[key] = lru_queue.cbegin();
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}
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void Touch(const Key& key) override
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{
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// move the touched element at the beginning of the lru_queue
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lru_queue.splice(lru_queue.cbegin(), lru_queue, key_finder[key]);
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}
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void Erase(const Key& key) override
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{
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// remove the least recently used element
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key_finder.erase(lru_queue.back());
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lru_queue.pop_back();
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}
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// return a key of a displacement candidate
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const Key& ReplCandidate() const override
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{
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return lru_queue.back();
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}
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// return a key of a displacement candidate
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void Clear() override
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{
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lru_queue.clear();
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key_finder.clear();
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}
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private:
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std::list<Key> lru_queue;
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std::unordered_map<Key, lru_iterator> key_finder;
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};
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} // namespace caches
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#endif // LRU_CACHE_POLICY_HPP
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