//this fun create a new threadpool   
xx_thread_pool xx_threadpool_create(int min_threadnum,int max_threadnum);   
 
//add a new task into threadpool   
int xx_threadpool_add(xx_thread_pool pool,XX_ThreadFun func,void *arg);  
 
//stop and delete the threadpool   
int xx_threadpool_del(xx_thread_pool pool);