iOS CRC16校验

+(uint16_t)calculateCRC:(NSData *)data start:(int)start end:(int)end{
    Byte *bts = (Byte *)[data bytes];
    uint16_t crc = (short) 0x0000;
    uint8_t i;
    for (int ii = start; ii <= end; ii++) {
        crc = crc ^ (bts[ii] << 8);
        for (i = 0; i < 8; i++) {
            if (crc & 0X8000) {
                crc = (crc << 1) ^ 0x1021;
            } else {
                crc <<= 1;
            }
        }
        crc &= 0XFFFF;
    }
    return crc;
}

NSData *data = [@"abc" dataUsingEncoding:NSUTF8StringEncoding];
uint16_t res = [BluetoothManager calculateCRC:data start:0 end:2];
NSLog(@"calculateCRC %04x", res);