node.js - 可读流的_read函数在nodejs中有什么作用？

Question

我正在阅读文档并且有这个描述，但我不明白它的意思。

All Readable stream implementations must provide a _read method to fetch data from the underlying resource.

This method is prefixed with an underscore because it is internal to the class that defines it, and should not be called directly by user programs. However, you are expected to override this method in your own extension classes.

When data is available, put it into the read queue by calling readable.push(chunk). If push returns false, then you should stop reading. When _read is called again, you should start pushing more data.

底层资源是什么？你什么时候会真正指定一个 _read 函数，这意味着它有什么作用？

Answer 1

_read() 函数用于通知 Readable 流尚未达到 highWaterMark 并且该流可以随意从底层读取更多数据资源。传递给 _read() 的参数是建议从底层资源读取的字节数(或者在 objectMode 情况下的项目数)。

文档中提到的基础资源是指任何数据源。它可以是任何东西，包括另一个可读流，也可以是您动态生成的数据(例如，提供随机二进制数据的可读流)。