<number> 内部缓冲区的最大长度。如果写入操作导致缓冲区超过 maxLength，则写入的数据将被丢弃，并触发 drop 事件，其中包含丢弃的数据。
¥<number> The maximum length of the internal buffer. If a write
operation would cause the buffer to exceed maxLength, the data written is
dropped and a drop event is emitted with the dropped data.