I note (now :-) that QueueAsyncCall() works on a strictly LIFO basis, i.e. it's really a stack rather than a queue.

Has anybody ever built a simple round-robin scheduler based on this, for example to handle low-speed comms on an indeterminate number of serial ports?

Which revision of lazarus? IIRC it was very recently changed (corrected) to FIFO.

0.9.28.3. I saw the discussion from earlier in the year, but I was specifically considering code that could handle several serial ports pseudo-concurrently while being able to display messages etc. using visual controls. Obviously I could go for a full-blooded multithreaded solution, but async calls work very well for one port at a time...

Maybe look at trunk, I don't know if that ever went into any branch.

Revision: 25698
Date: 16:29:53, 27 May 2010
Message: Change ASyncQueue to run in forward order (first in / first out)

Mark Morgan Lloyd wrote

I note (now :-) that QueueAsyncCall() works on a strictly LIFO basis, i.e. it's really a stack rather than a queue.

hunh? i thought a queue was an orderly format already... just like a stack... like getting in the queue to get on the metro or to enter the stadium to see your favorite band or to even buy lunch ;)

i must admit that i don't see the apparent difference :?

Has anybody ever built a simple round-robin scheduler based on this, for example to handle low-speed comms on an indeterminate number of serial ports?

i haven't, yet :P

So I take it you'd be happy if the last person to join the queue was always the first to be served, possibly taking the place of somebody currently /being/ served. Whatever, that aspect is apparently being changed.

I'm planning a crude hack, hopefully just a list of TDataEvent with control being distributed by a shim in a single async call procedure. However I've got some system management work that's intruding...

You did see my mail, that this was changed in Revision 25698?

So you can now, use QueueAsyncCall to *queue* several events, for several comms, and they will be executed first-in, first-out.

Martin

Martin wrote

You did see my mail, that this was changed in Revision 25698? So you can now, use QueueAsyncCall to *queue* several events, for several comms, and they will be executed first-in, first-out.

Yes, I did. And if I understand things correctly each will be executed to completion, first in first out, so it's not very much help for something that needs to loop.

Well each called function/procedure must voluntary return anyway (if you do not use threads). So if a method returns, it just adds itself to the end of the list again => and that way you keep looping.

I've done exactly that myself (but with only one method), instead of ProcessMessages, the method reschedules itself.

Yes, I agree that that's probably a valid way of implementing it.

yeah, it was later that i caught the LIFO vs FIFO flow... my above is mainly that a stack and a queue are, at least to me, the same but then i always do FIFO except in extremely rare cases...

don'cha hate it when that happens? ;)