From 4952e2b4d22958aa374f7f61813326ab4159e86d Mon Sep 17 00:00:00 2001 From: fresheneesz Date: Thu, 25 Jun 2015 16:05:40 -0700 Subject: [PATCH] doc: clarify Readable._read and Readable.push Minor clarifications around Readable._read and Readable.push to make their implementation/usage easier to understand. https://github.com/joyent/node/issues/14124#issuecomment-115392674 Reviewed-By: James M Snell PR-URL: https://github.com/joyent/node/pull/25591 --- doc/api/stream.markdown | 45 ++++++++++++++++++----------------------- 1 file changed, 20 insertions(+), 25 deletions(-) diff --git a/doc/api/stream.markdown b/doc/api/stream.markdown index 42cb7e3d702..0ab98a863bb 100644 --- a/doc/api/stream.markdown +++ b/doc/api/stream.markdown @@ -944,24 +944,22 @@ initialized. * `size` {Number} Number of bytes to read asynchronously -Note: **Implement this function, but do NOT call it directly.** +Note: **Implement this method, but do NOT call it directly.** -This function should NOT be called directly. It should be implemented -by child classes, and only called by the internal Readable class -methods. +This method is prefixed with an underscore because it is internal to the +class that defines it and should only be called by the internal Readable +class methods. All Readable stream implementations must provide a _read +method to fetch data from the underlying resource. -All Readable stream implementations must provide a `_read` method to -fetch data from the underlying resource. +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. -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. +Note: once the `_read()` method is called, it will not be called again until +the `push` method is called. The `size` argument is advisory. Implementations where a "read" is a single call that returns data can use this to know how much data to @@ -977,19 +975,16 @@ becomes available. There is no need, for example to "wait" until Buffer encoding, such as `'utf8'` or `'ascii'` * return {Boolean} Whether or not more pushes should be performed -Note: **This function should be called by Readable implementors, NOT +Note: **This method should be called by Readable implementors, NOT by consumers of Readable streams.** -The `_read()` function will not be called again until at least one -`push(chunk)` call is made. - -The `Readable` class works by putting data into a read queue to be -pulled out later by calling the `read()` method when the `'readable'` -event fires. +If a value other than null is passed, The `push()` method adds a chunk of data +into the queue for subsequent stream processors to consume. If `null` is +passed, it signals the end of the stream (EOF), after which no more data +can be written. -The `push()` method will explicitly insert some data into the read -queue. If it is called with `null` then it will signal the end of the -data (EOF). +The data added with `push` can be pulled out by calling the `read()` method +when the `'readable'`event fires. This API is designed to be as flexible as possible. For example, you may be wrapping a lower-level source which has some sort of