实现可读流
stream.Readable
类被扩展以实现 Readable
流。
自定义 Readable
流必须调用 new stream.Readable([options])
构造函数并实现 readable._read()
方法。
The stream.Readable
class is extended to implement a Readable
stream.
Custom Readable
streams must call the new stream.Readable([options])
constructor and implement the readable._read()
method.