code: public static Optional<Byte> readMaybeByte(ByteBuf bf) {
        if (bf.readableBytes() >= 1) {
           return Optional.of(bf.readByte());
        } else {
           bf.resetReaderIndex();
           return Optional.empty();
        }
     }
docs: Reads a byte if possible.  If not present the reader index is reset to the last mark.
  
  @param bf
  @return