用C++实现一个LRU cache

#include <boost/unordered_map.hpp>#define DEFAULT_LRU_CAPACITY 10000template<class K, class V>class LRUCache{struct Node{K key;V value;Node *prev, *next;Node(const K& key, const V& value): key(key), value(value){prev = next = NULL;}Node(){}};public:LRUCache(std::size_t size = DEFAULT_LRU_CAPACITY): size_(size){//Mutex::Lock autolock(lock);assert(size > 0);head_ = new Node;head_->next = head_;head_->prev = head_;//circle}int get(const K& k, V& v){//Mutex::Lock autolock(lock);boost::unordered_map<K, Node*>::const_iterator iter = elems_.find(k);if (iter == elems_.end()) {cout << "get, cannot find:" << k << endl;return -1; //can't find}Node* node = iter->second;if (head_->next != node) {detatch(node);attach(node);}v = node->value;return 0;}int put(const K key, const V& value){//Mutex::Lock autolock(lock);if (elems_.find(key) != elems_.end()) {return -1; //not unique}if (elems_.size() >= size_){drop_oldest();}Node* node = new Node(key, value);elems_[key] = node;attach(node);return 0;}void dump(){std::cout << "dump-----------------------" << endl;Node* node = head_->next;while (node && node != head_) {std::cout << "------------\t" << node->key << "\t" << node->value << endl;node = node->next;}}protected:void detatch(Node* node){node->prev->next = node->next;node->next->prev = node->prev;}void attach(Node* node){node->next = head_->next;node->prev = head_;head_->next->prev = node;head_->next = node;}void drop_oldest(){Node* node = head_->prev;// last nodeassert(node != head_);// not emptyif (node == head_) {return;// empty}K key = node->key;elems_.erase(key);head_->prev = node->prev;node->prev->next = head_;delete node;}protected:boost::unordered_map<K, Node*> elems_;Node* head_;std::size_t size_;//Mutex lock;};