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做项目遇到需要使用到键值对的，一般我们会优先考虑map,multimap。

最近在看cocos2d-x源码，发现了一个更高效的用法uthash

头文件uthash.h在cocos2dx\support\data_support\下可以找到

下面是一个简单的使用：

#include "uthash.h"#include 
   
    #include 
    
     /*这个uthash必须构造一个结构体*/struct packet{	int key;            /*这个是用来做hash的key值*/	char msg[10]; 	UT_hash_handle hh; /*这个结构是uthash的结构体，里面包含next，prev，hash值等信息*/};int main(){	struct packet *pkt, *tmp;	int i;	struct packet *hash_packet = NULL; /*必须初始化为NULL*/	/*打印这个hash的节点数*/	printf ("hash count = %d \n", HASH_COUNT(hash_packet));	/*往hash中添加节点*/	for (i=0; i<10; i++)	{		pkt = (struct packet *)malloc(sizeof(struct packet));		pkt->key = i;		sprintf (pkt->msg, "i=%d", i);		HASH_FIND_INT(hash_packet, &i, tmp);		if (tmp != NULL)		{			printf ("The key(%d) exists in hash. \n", i);			continue;		}		HASH_ADD_INT(hash_packet, key, pkt);		printf ("insert item. key=%d,value=%p \n", i, pkt);	}	printf ("hash count = %d \n", HASH_COUNT(hash_packet));	/*通过key查找*/	for (i=0; i<13; i++)	{		HASH_FIND_INT(hash_packet, &i, tmp);		if (tmp == NULL)		{			printf ("find not item. key=%d,value=%p \n", i, tmp);			continue;		}		printf ("find item. key=%d,value=%p \n", i, tmp);	}	printf ("hash count = %d \n", HASH_COUNT(hash_packet));	/*遍历这个hash表*/	struct packet* mytemp = NULL;	for (mytemp = hash_packet; mytemp != NULL; mytemp = (packet*)mytemp->hh.next)		printf (" %d => %s \n", mytemp->key, mytemp->msg);	/*删除节点*/	for (i=0; i<13; i++)	{		HASH_FIND_INT(hash_packet, &i, tmp);		if (tmp == NULL)		{			printf ("find not item. key=%d,value=%p \n", i, tmp);			continue;		}		/*删除节点不会释放你的空间必须自己释放*/		HASH_DEL(hash_packet, tmp);		free(tmp);		printf ("delete itme. key=%d,value=%p \n", i, tmp);	}	printf ("hash count = %d \n", HASH_COUNT(hash_packet));	system("pause");	return 0;}
    
   

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