doc,stream: _transform happens one at a time

Add a note to the stream docs specifying that at most a single call to _transform can happen, and the provided callback() should be used to process another chunk. Fixes: #3208 PR-URL: #14321 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Colin Ihrig <[email protected]>
nodejs · Jul 24, 2017 · 53ad91c · 53ad91c
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commit 53ad91c
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diff --git a/doc/api/stream.md b/doc/api/stream.md
@@ -2033,6 +2033,10 @@ The `transform._transform()` method is prefixed with an underscore because it
 is internal to the class that defines it, and should never be called directly by
 user programs.
 
+`transform._transform()` is never called in  parallel; streams implement a
+queue mechanism, and to receive the next chunk, `callback` must be
+called, either synchronously or asychronously.
+
 #### Class: stream.PassThrough
 
 The `stream.PassThrough` class is a trivial implementation of a [Transform][]