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List: freedesktop-dbus
Subject: Re: dbus questions
From: Gordon Tyler <gordon () doxxx ! net>
Date: 2003-12-09 16:23:58
Message-ID: 3FD5F71E.7080405 () doxxx ! net
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David Zeuthen wrote:
> 2. Message dependencies
>
> I have an situation where I know that I will receive several messages,
> but one of
> the early messages need to wait for a later message to have been processed,
> before the early message itself can be processed (possibly with some
> timeout).
>
> How is this easiest achieved? I suppose the only answer is go
> multithreaded (even
> though I really want to avoid this); Is D-BUS designed to do this? I
> can't seem to
> find anything useful about this in the docs..
I get the impression that this is not within D-BUS' domain. It's an
application-level requirement which you could probably achieve without
multi-threading by using a queue-like system:
1. You receive message A but you determine that it requires message B to
be processed first. You push it onto the queue, making a note of its
dependencies and continue listening for messages.
2. You receive message B but you determine that it requires message C to
be processed first. You also push it onto the queue and continue
listening for messages.
3. You receive message C that has no dependencies. You process it:
a. You search through the queue in most-recent-to-oldest order,
looking for a message that depends on the message being processed,
finding message B.
b. Having found message B, you make a note in the message that it's
message C dependency has been satisified.
c. Since message B has had all its dependencies satisfied, you
process it as above.
d. Continue searching for a message which depends on message C.
Or something along those lines. Some provision would have to be made to
keep track of situations like message C arriving first.
Ciao,
Gordon
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