namespace ErvProtocol
{
    // CRC-16/MODBUS (poly 0xA001 reflected, init 0xFFFF)
    // PC_ERV_Protocol.md 1장 - CMD~PAYLOAD 구간, 결과 리틀엔디안
    public static class Crc16
    {
        public static ushort Modbus(byte[] data, int start, int length)
        {
            ushort crc = 0xFFFF;
            for (int i = 0; i < length; i++)
            {
                crc ^= data[start + i];
                for (int b = 0; b < 8; b++)
                    crc = (crc & 0x0001) != 0 ? (ushort)((crc >> 1) ^ 0xA001) : (ushort)(crc >> 1);
            }
            return crc;
        }
    }
}