Re: [SDLTF-Members] SDL-News: SAVE: Request for additional feedback

Subject: Re: [SDLTF-Members] SDL-News: SAVE: Request for additional feedback
From: Susanne Graf (
Date: Thu Jan 08 2004 - 16:10:56 GMT

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Indeed, discarding signals which have to be considered as "old" is difficult in
SDL, and this has nothing to do with the save construct. What would be needed is
not to eliminate the SAVE construct, but to add the possibility to discard
signals satisfying some "old" criterion, and this should not only depend on the
signal typ, but on its parameters (which might contain a sequence number, a time
stamp, ...).
Obviously, this doesn't make things simpler but more complicated. But you are
right, the identified problem is a real problem.


Rick Reed TSE wrote:
> William H. Skelton at wrote on 01/08/04 13:04:
>>A problem has been identified that there is no atomic way to flush signals
>>that have been saved. For example, if a signal E1 is saved, then E2 arrives
>>causes a reset of the state machine, then another E1 arrives, there is no way
>>to flush at the time of the reset the saved E1 without losing the new E1.
> Even without SAVE it is not clear how this can be achieved. If we assume
> that the each E1 is buffered internally, when E2 is received the buffer
> could be cleared as part of the reset. If when E2 is received there was an
> E1 in the input queue, this would have arrived BEFORE the reset, but would
> NOT be in the internal buffer and would NOT be cleared. Discarding the E1
> after the reset would also mean that any E1 signals arriving after the reset
> would also be discarded.
> --
> Rick Reed -
> Tel:+44 15394 88462 Mob.:+44 7970 50 96 50

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