//本函数 为CRC16校验
//data为数据地址,len为长度
static int icmp_cksum(void *data, int len)
{int nleft = len;
uint16_t *data_tmp = (uint16_t *)data;
int sum = 0; //校验和存储变量
uint16_t tmp = 0;
//以2字节为一数据累加
while(nleft > 1){
sum += *data_tmp++;
nleft -= 2;
}
//如果是奇数个字节,最后字节如下处理
if(nleft == 1){
*(uint8_t *)(&tmp) = *(uint8_t *)data_tmp;
sum += tmp;
}
sum = (sum >> 16) + (sum &0xffff);
sum += (sum >> 16);
tmp = ~sum; //取反
return tmp;
}