According the documentation
http://www.isd.mel.nist.gov/projects/rcslib/NMLcpp.html there is a
blocking_read() function that internally waits until it is signalled that
there is a message to be read. You can either look into the blocking_read
implementation to see if the events/fds are exposed, or set up your own
background thread to do wait.
Frank
_____
From: Maxime Lemonnier [mailto:maxime.lemonn...@gmail.com]
Sent: Saturday, 1 August 2009 8:37 AM
To: EMC developers
Subject: [Emc-developers] RCS/CMS/NML question
Hi,
I'm looking for someone familiar enough with the RCS/CMS/NML subsystem.
I'm looking for a way to implement the observer pattern so, what I'd need is
a way to register some callback function(s) when shared memory is written.
This is where I'm starting from :
[17:54] <alex_joni> in cms/cms_in.cc
[17:55] <alex_joni> you can probably (somehow) add your callback there
[17:55] <alex_joni> the write_raw gets called when a new function gets
written to the unbuffered channel
[17:55] <alex_joni> and queue_write_raw gets called for buffered channels
It appears that the
CMS_STATUS CMS::write_XXX
family of function would be the right places to add a callbacks queue, but I
still don't know what to do with queued writes, I'll continue to
investigate. Also, I'm looking for a good place in the server to execute my
callbacks, when idle for instance. I don't want the write function to wait
for my callback to return, which would slow down the server.
At worst I'll spawn a thread, but that means semaphores, so I'd rather used
an existing facility.
Any other input would be welcome
Thank you,
(I'm still working on a PyQ4t-based gui project, it is going on well, but
poll-based refresh is a no go for a project which main intent is a cleaner
design.)
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