// LRU(最近最少使用)緩存機制
#ifndef _ZD_LRU_CACHE_H_
#define _ZD_LRU_CACHE_H_#include <unordered_map>
#include <list>
#include <mutex>class ZDLRUCahce
{
public:ZDLRUCahce(int capacity): m_capacity(capacity){}~ZDLRUCahce(){}// 1.key不存在,返回-1// 2.key存在,list中刪除key,在list頭部重新插入,更新mapint Get(int key){RecursiveGuard mtx(m_recursive_mutex);auto it = m_mapCache.find(key);if (it == m_mapCache.end())return -1;std::pair<int, int> kv = *m_mapCache[key];m_listCache.erase(m_mapCache[key]);m_listCache.push_front(kv);m_mapCache[key] = m_listCache.begin();return kv.second;}// 1.key存在:刪除該key,在list頭部插入數據,更新map// 2.key不存在 2.1 容量未滿:在list頭部插入數據,更新map 2.2 容量已滿:刪除list尾部數據,在list頭部重新插入數據,,更新mapvoid Put(int key, int value){RecursiveGuard mtx(m_recursive_mutex);auto it = m_mapCache.find(key);if (it != m_mapCache.end()){m_listCache.erase(m_mapCache[key]);m_listCache.push_front(std::make_pair(key, value));m_mapCache[key] = m_listCache.begin();return;}if (m_listCache.size() == m_capacity){auto iter = m_listCache.back();m_mapCache.erase(iter.first);m_listCache.pop_back();m_listCache.push_front(std::make_pair(key, value));m_mapCache[key] = m_listCache.begin();}else{m_listCache.push_front(std::make_pair(key, value));m_mapCache[key] = m_listCache.begin();}}private:int m_capacity;typedef std::lock_guard<std::recursive_mutex> RecursiveGuard;typedef std::list<std::pair<int, int>> Cache;typedef std::unordered_map<int, Cache::iterator> CacheMap;std::recursive_mutex m_recursive_mutex;Cache      m_listCache;CacheMap   m_mapCache;
};#endif