[FFmpeg-devel] [RFC] Event loop

[Mark Thompson]

On 17/02/2021 20:57, Nicolas George wrote:
> Mark Thompson (12021-02-17):
>> I can see that this is all sensible stuff on Unix, but can you explain
>> a bit more of what your Windows implementation is going to look like?
> 
> I have no intention to write Windows code for this. Our current
> protocols use poll() internally, this event loop will do the same, and
> be exactly as portable as things are now.
> 
> But it will be modular: if somebody later wants to write specific code
> for Windows, it will be possible and I will make sure it is as easy as
> possible.
> 
> Does that sound acceptable?

I'm not sure you can avoid writing Windows code for this to work at all, because I don't think poll() as we have now is sufficient to get the functionality you want.

I also worry that codifying something in this form is going to exclude the possibility of getting a better result on Windows later, because that wouldn't involve file descriptors or internals calling default BSD send()/recv().

For example:

On 01/02/2021 19:14, Nicolas George wrote:
 >      The API would consist of just a few entry points:
 >
 >      - allocate, init, free an AVScheduler;
 >      - allocate, add, alter, remove, free events;
 >      - start, run, stop the loop.

How are you going to implement altering/removing an event or stopping the loop?

On Unix you of course have an eventfd/self-pipe sitting in the poll() set on the event loop to interrupt it.  On Windows you can't, because those things are not file descriptors.

- Mark