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| #pragma once
#include <list>
#include <unordered_map>
#include <mutex>
#include <memory>
template <typename K, typename V>
class LRUCache
{
private:
using Cache = std::list<std::pair<K, V>>;
Cache cache;
std::unordered_map<K, typename Cache::iterator> um;
const size_t capacity;
std::unique_ptr<std::mutex> mtx;
public:
LRUCache(size_t capacity) : capacity(capacity),mtx{new std::mutex()} {}
template <typename K1>
V *get(K1 &&key)
{
std::unique_lock<std::mutex> ul{*mtx};
auto it = um.find(std::forward<K1>(key));
if (it == um.end())
{
return nullptr;
}
cache.splice(cache.end(), cache, it->second);
return &it->second->second;
}
template <typename K1, typename V1>
void put(K1 &&key, V1 &&value)
{
if (capacity == 0)
{
return;
}
std::unique_lock<std::mutex> ul{*mtx};
auto it = um.find(std::forward<K1>(key));
if (it == um.end())
{
if (cache.size() == capacity)
{
um.erase(cache.front().first);
cache.pop_front();
}
auto cache_it = cache.emplace(cache.end(), std::forward<K1>(key), std::forward<V1>(value));
um.emplace(cache_it->first, cache_it);
}
else
{
it->second->second = std::forward<V1>(value);
cache.splice(cache.end(), cache, it->second);
}
}
};
|