scodec XOR checksum Codec

XorChecksumCodec.scala

object XorChecksumCodec {

  def xorByte(bits: BitVector): BitVector = BitVector(bits.bytes.foldLeft[Byte](0)((a, b) => (a ^ b).asInstanceOf[Byte]))

  def apply[T](target: Codec[T]) = checksummed(target, xorByte, trailer(target), true)

  def trailer[T](target: Codec[T]): Codec[(BitVector, BitVector)] = new Codec[(BitVector, BitVector)] {
    def sizeBound = target.sizeBound + new SizeBound(0, Some(8L))
    def encode(value: (BitVector, BitVector)): Attempt[BitVector] = Attempt.successful(value._1 ++ value._2)
    def decode(bits: BitVector): Attempt[DecodeResult[(BitVector, BitVector)]] =
      Attempt.successful(DecodeResult((bits.dropRight(8), bits.takeRight(8)), BitVector.empty))
  }

}