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77 lines
1.7 KiB
77 lines
1.7 KiB
#ifndef LFU_CACHE_POLICY_HPP
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#define LFU_CACHE_POLICY_HPP
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#include <cstddef>
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#include <unordered_map>
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#include <map>
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#include <iostream>
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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 LFUCachePolicy : public ICachePolicy<Key>
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{
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public:
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using lfu_iterator = typename std::multimap<std::size_t, Key>::iterator;
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LFUCachePolicy() = default;
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~LFUCachePolicy() override = default;
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void Insert(const Key& key) override
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{
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constexpr std::size_t INIT_VAL = 1;
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// all new value initialized with the frequency 1
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lfu_storage[key] = frequency_storage.emplace_hint(
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frequency_storage.cbegin(), INIT_VAL, key);
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}
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void Touch(const Key& key) override
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{
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// get the previous frequency value of a key
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auto elem_for_update = lfu_storage[key];
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auto updated_elem = std::make_pair(
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elem_for_update->first + 1, elem_for_update->second);
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// update the previous value
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frequency_storage.erase(elem_for_update);
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lfu_storage[key] = frequency_storage.emplace_hint(
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frequency_storage.cend(), std::move(updated_elem));
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}
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void Erase(const Key& key) override
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{
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frequency_storage.erase(lfu_storage[key]);
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lfu_storage.erase(key);
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}
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const Key& ReplCandidate() const override
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{
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// at the beginning of the frequency_storage we have the
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// least frequency used value
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return frequency_storage.cbegin()->second;
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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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frequency_storage.clear();
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lfu_storage.clear();
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}
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private:
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std::multimap<std::size_t, Key> frequency_storage;
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std::unordered_map<Key, lfu_iterator> lfu_storage;
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};
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} // namespace caches
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#endif // LFU_CACHE_POLICY_HPP
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