@Override
  public int readUnsignedByteScalar() {
    checkScalar("unsigned byte scalar", 1);
    int result = (currentPayloadSize == 0) ? 0 : payloadByte(0) & 0xff;
    setTo(nextItem());
    return result;
  }
Sets the input to the item provided (an offset to the beginning of an item) and check this is
valid.

@param item the value to which the current item is to be set.
ethereum/rlp/src/main/java/org/hyperledger/besu/ethereum/rlp/AbstractRLPInput.java