当C++遇到IOS应用开发---LRUCache缓存(3)

template <> 
struct hashkey_compare<HashKey> 
{ 
    bool operator()(HashKey __x, HashKey __y) const{ 
        string x = [__x.key UTF8String]; 
        string y = [__y.key UTF8String]; 
        return x < y; 
    } 
}; 
        
//自定义map类型 
template <typename K, typename V, typename _Compare = hashkey_compare<K>, 
typename _Alloc = std::allocator<std::pair<const K, V> > > 
class  lru_map: public map<K, V, _Compare, _Alloc>{}; 
            
class CLRUCache 
{ 
public: 
    
    CLRUCache() : _now(0){ 
        _lru_list = shared_ptr<lru_map<virtual_time, HashKey> >(new lru_map<virtual_time, HashKey>); 
        _hash_table = shared_ptr<lru_map<HashKey, HashValue> > (new lru_map<HashKey, HashValue>); 
    } 
    
    ~CLRUCache(){ 
        _lru_list->clear(); 
        _hash_table->clear(); 
    } 
    
    int set( const HashKey& key, const id &value ) 
    { 
        HashValue hash_value; 
        hash_value.value_ = value; 
        hash_value.access_ = get_virtual_time(); 
        pair< map<HashKey, HashValue>::iterator, bool > ret = _hash_table->insert(make_pair(key, hash_value)); 
        if ( !ret.second ){ 
            // key already exist 
            virtual_time old_access = (*_hash_table)[key].access_; 
            map<virtual_time, HashKey>::iterator iter = _lru_list->find(old_access); 
            if(iter != _lru_list->end()) 
            { 
                _lru_list->erase(iter); 
            }