code: function($buf) {
        if ($buf.length < 20) throw new IncorrectBufferSizeError(20, $buf.length);
        return {
          a: $buf.slice(0, 5),
          b: $buf.slice(5, 15),
          c: $buf.slice(15, 20).toString(),
          d: $buf.slice(20).toString(),
        };
      }
docs: 严格模式的解码器