在学习Node.js的时候,查看官网文档,关于readable._read(size)这个API,官网中有如下的这段话:
When _read is called, if data is available from the resource, _read should start pushing that data into the read queue by calling this.push(dataChunk). _read should continue reading from the resource and pushing data until push returns false, at which point it should stop reading from the resource. Only when _read is called again after it has stopped should it start reading more data from the resource and pushing that data onto the queue.
Note: once the _read() method is called, it will not be called again until the push method is called.
问题如下:
为什么_read会触发push操作?
_read为什么会设计成关联push的操作?
1）_read方法作为底层借口由你自己实现readable接口的时候实现，不能直接调用
2）_read方法从底层数据流中读取数据内容，然后通过push方法放入用户的数据消费队列中，直到用户数据消费队列满。此时数据的读取动作就为停止。
3）当用户消费队列中的数据在用户通过监听data事件获取到后，_read方法会被再次调用，填充用户数据消费队列
4）这个过程一直持续到读到数据末尾位置
_read方法是需要在实现自己的readable流对象的时候实现的，是底层系统调用触发的。你不好直接调用~~~