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User:Brahmana/Netwerk Docs/Stream Operations: Difference between revisions
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User:Brahmana/Netwerk Docs/Stream Operations (view source)
Revision as of 17:45, 4 January 2009
, 4 January 2009Answers to questions
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The Stream is a straight forward thing and here it represents a stream of data that can be read. The stream can be blocking or non-blocking. Lets assume for now that it is not | The Stream is a straight forward thing and here it represents a stream of data that can be read. The stream can be blocking or non-blocking. Lets assume for now that it is not | ||
blocking. Now the standard way of reading from the stream would be to poll the stream at some regular intervals and ask it if there is some data. If it says yes then we call read. | blocking. Now the standard way of reading from the stream would be to poll the stream at some regular intervals and ask it if there is some data. [<i>Actually the standard way is to QueryInterface the stream for nsIAsyncInputStream and use asyncWait; regular polling is only necessary if you want to use a nonblocking stream that doesn't support nsIAsyncInputStream, which is rare. A blocking stream that doesn't support nsIAsyncInputStream can of course simply be read on a background thread. [[User:Biesi|Biesi]] 17:45, 4 January 2009 (UTC)</i>] If it says yes then we call read. | ||
To avoid this, there are stream listeners, The Listener in our case. The Listener provides methods to notify it of Start, Stop and data availability. Now we would expect The Stream to take this listener and call the methods on it. But that is not how it works here. Probably because it is not a good to tie the listener with Stream. Honestly I do not know the precise reason. It might have something to do with blocking streams. Basically you cannot just directly pass a listener to a stream and ask it to notify you when there is data. '''[biesi: Any explanation?]''' | To avoid this, there are stream listeners, The Listener in our case. The Listener provides methods to notify it of Start, Stop and data availability. Now we would expect The Stream to take this listener and call the methods on it. But that is not how it works here. Probably because it is not a good to tie the listener with Stream. Honestly I do not know the precise reason. It might have something to do with blocking streams. Basically you cannot just directly pass a listener to a stream and ask it to notify you when there is data. '''[biesi: Any explanation?]''' [<i>There's nsIAsyncInputStream, see above. That said, streamlistener semantics are somewhat complicated so it makes sense not to require all streams to be able to handle them. [[User:Biesi|Biesi]] 17:45, 4 January 2009 (UTC)</i>] | ||
This is where The Pump comes into picture. The pump takes a stream and a listener and plays the mediator between the two. It basically factors out the responsibility of | This is where The Pump comes into picture. The pump takes a stream and a listener and plays the mediator between the two. It basically factors out the responsibility of | ||
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EnsureWaiting(). Since we get one notification for every call to asyncWait(), EnsureWaiting() is called after processing every callback notification. | EnsureWaiting(). Since we get one notification for every call to asyncWait(), EnsureWaiting() is called after processing every callback notification. | ||
With this the user of this stream can create a StreamPump and pass his listener to it. The pump will then notify the listener about the Start, Stop and availability of data. | With this the user of this stream can create a StreamPump and pass his listener to it. The pump will then notify the listener about the Start, Stop and availability of data. [<i>Well, the pump itself handles that too, the user doesn't have to create the nsITransport themselves. [[User:Biesi|Biesi]] 17:45, 4 January 2009 (UTC)</i>] | ||