package crc4

func Checksum(b []byte) uint8 {
        crc := 0xFFFF
        for bI := 0; bI < len(b); bI++ {
                bit := uint8(0x80)
                for bitI := 0; bitI < 8; bitI++ {
                        xorFlag := ((crc & 0x8000) == 0x8000)
                        crc = crc << 1
                        if ((b[bI] & bit) ^ uint8(0xFF)) != uint8(0xFF) {
                                crc = crc + 1
                        }

                        if xorFlag {
                                crc = crc ^ 0x1021
                        }

                        bit = bit >> 1
                }
        }
        return uint8(crc)
}