[Twisted-Python] Fwd: [Twisted-commits] r11032 - Made LineReceiver about 3x as fast, and clarified some of the docstrings.

[James Y Knight]

On Jun 18, 2005, at 2:58 PM, Jp Calderone wrote:
> This changes dataReceived to call down into user code while the  
> LineReceiver's instance attributes are in an inconsistent state.   
> This can lead to duplicate data delivery if dataReceived is called  
> into from lineReceived.  Normally this sounds like a ridiculous  
> thing to do, but notice the implementation of resumeProducing():
>
>     def resumeProducing(self):
>         self.paused = False
>         self.dataReceived('')
>         self.transport.resumeProducing()
>
> Since resumeProducing is called immediately when a producer is  
> registered, this means LineReceivers can no longer register  
> themselves as producers for their transports from lineReceived,  
> which is a much more reasonable thing to do.
>
> Demonstration of the bug in action attached.

Two things about that:
1) resumeProducing actually now says:
     def resumeProducing(self):
         self.paused = False
         self.transport.resumeProducing()
         self.dataReceived('')

This was changed because of <http://twistedmatrix.com/pipermail/ 
twisted-python/2005-February/009626.html> also <http:// 
twistedmatrix.com/bugs/issue899>.

However, if resumeProducing is allowed to immediately produce data,  
this is somewhat bogus, as it could reverse the order of the data. In  
reality, a TCP transport's resumeProducing will not immediately  
produce data, but I think that's a fragile API to both have  
resumeProducing immediately produce data, and depend on a call to  
someone else resumeProducing not immediately producing data. I think  
there's an issue here.

2) dataReceived can be easily fixed to handle this by using a local  
-- patch coming separately.

James