LRU cache实现，还是使用伪头部和伪尾部节点写代码更加简单

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class Node:     def __init__(self, key, val):         self.key = key         self.val = val         self.prev = None         self.next = None   class LRUCache:     def __init__(self, capacity):         self.capacity = capacity         self.hashmap = {}         # 使用伪头部和伪尾部节点         self.head = Node(0, 0)         self.tail = Node(0, 0)         self.head.next = self.tail         self.tail.prev = self.head       def get(self, key):         if key in self.hashmap:             node = self.hashmap[key]             self._remove(node)             self._add(node)             return node.val         return -1       def put(self, key, value):         if key in self.hashmap:             self._remove(self.hashmap[key])         node = Node(key, value)         self._add(node)         self.hashmap[key] = node         if len(self.hashmap) > self.capacity:             node = self.head.next             self._remove(node)             del self.hashmap[node.key]       def _remove(self, node):         prev = node.prev         next = node.next         prev.next = next         next.prev = prev       def _add(self, node):         prev = self.tail.prev         prev.next = node         self.tail.prev = node         node.prev = prev         node.next = self.tail   # 创建一个容量为2的LRU缓存 cache = LRUCache(2)   # 插入键值对("192.168.1.1", 1) cache.put("192.168.1.1", 1) assert cache.get("192.168.1.1") == 1  # 返回1   # 插入键值对("192.168.1.2", 2) cache.put("192.168.1.2", 2) assert cache.get("192.168.1.2") == 2  # 返回2   # 再次访问键"192.168.1.1" assert cache.get("192.168.1.1") == 1  # 返回1   # 插入键值对("192.168.1.3", 3)，这会导致键"192.168.1.2"被删除，因为它是最近最少使用的键 cache.put("192.168.1.3", 3) assert cache.get("192.168.1.2") == -1  # 返回-1，因为键"192.168.1.2"已经被删除   # 再次访问键"192.168.1.1" assert cache.get("192.168.1.1") == 1  # 返回1   # 插入键值对("192.168.1.4", 4)，这会导致键"192.168.1.3"被删除，因为它是最近最少使用的键 cache.put("192.168.1.4", 4) assert cache.get("192.168.1.3") == -1  # 返回-1，因为键"192.168.1.3"已经被删除

　　

核心：

（1）只要访问过，或者新节点，就将节点放到tail，区别无非是访问的节点修改前后link；

（2）只要是删除，就将节点从head里remove。

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void lru_add_to_tail(struct brief_asset_info *node) {     // 将对应的节点添加到双向链表的尾部，作为LRU的最新节点     node->prev = g_asset_portray_lru.dummy_tail->prev;     node->next = g_asset_portray_lru.dummy_tail;     g_asset_portray_lru.dummy_tail->prev->next = node;     g_asset_portray_lru.dummy_tail->prev = node; }   void lru_move_to_tail(struct brief_asset_info *node) {     // 移动节点到到双向链表的尾部，作为LRU的最新节点     node->prev->next = node->next;     node->next->prev = node->prev;     lru_add_to_tail(node); }   struct brief_asset_info *lru_delete_head() {     struct brief_asset_info *node = g_asset_portray_lru.dummy_head->next;     g_asset_portray_lru.dummy_head->next = node->next;     node->next->prev = g_asset_portray_lru.dummy_head;     return node; }

　　

实际C代码应用伪代码：

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struct asset_nlog_ua *asset_check_iot_xxx(struct asset_info *info, bool *is_counterfeit) {     struct ip_mac ip_mac_key = {0};     ip_mac_key.ip = info->ip;     ip_mac_key.mac = info->mac;     struct ase_hash *asset_portray = g_asset_portray_lru.asset_portray_map;     struct brief_asset_info *found_info = asset_find_iot_portray(&ip_mac_key, asset_portray);     struct asset_nlog_ua *event = NULL;     if (found_info != NULL) {         if (check_asset_conflict(found_info, info)) {             // 误报检查，非误报才生成事件             if (!asset_check_counterfeit_false_alarm(&found_info->ip_mac_key.ip, &found_info->ip_mac_key.mac)) {                 *is_counterfeit = true;                 event = asset_generate_iot_event(found_info, info);                 // 刷新LRU cache，更新访问的最新资产                 lru_move_to_tail(found_info);                 return;             }         }           // 资产属性不冲突，或者冲突但属于误报，更新已经存在的画像         asset_update_iot_portray(info, found_info, asset_portray);         // 刷新LRU cache，更新修改后的最新资产         lru_move_to_tail(found_info);     } else {         // 新建画像，需要考虑是否满规格，满规格情况下需要删除LRU中的老资产         if (g_asset_portray_lru.asset_portray_map->n_entry >= g_asset_portray_lru.capacity) {             ASE_INFO(ASE_CATE_ASSET, "[iot] asset_portray_map exceed max capacity, will asset_delete_oldest_portray.");             asset_delete_oldest_portray(asset_portray);         }           struct brief_asset_info *new_info = asset_insert_iot_portray(info, asset_portray);         // 刷新LRU cache，更新新建的最新资产         lru_add_to_tail(new_info);     }     return event; }