字符串hash fuction

资料：http://blog.csdn.net/liuben/article/details/5050697

1. 简单的方法：

unsigned int simple_hash(char *str)  
{  
    register unsigned int hash;  
    register unsigned char *p;  
  
    for(hash = 0, p = (unsigned char *)str; *p ; p++)  
        hash = 31 * hash + *p;  
  
    return (hash & 0x7FFFFFFF);  
}