code: private static int parseCode(ByteBuf buffer) {
          final int first = parseNumber(buffer.readByte()) * 100;
          final int second = parseNumber(buffer.readByte()) * 10;
          final int third = parseNumber(buffer.readByte());
          return first + second + third;
      }
docs: Parses the io.netty.handler.codec.smtp code without any allocation, which is three digits.