[ros-users] Shared memory image plugin

Cedric Pradalier cedric.pradalier at mavt.ethz.ch
Fri May 7 00:05:08 UTC 2010

Hi All,

I've just written a small shared-memory based image_transport_plugin 
using boost::interprocess and it raises 2 questions:

- First, I don't see how to write it efficiently while having the 
publish function const in image_transport/publisher.h. I currently wait 
to receive the first image to allocate the shared memory segment, and as 
far as I could tell, I can only do it in the publish function of the 
plugin, so this has to be non-const. Any reason why it would have to be 
const? Or any hint on how to achieve the same result while having the 
function const?

- Second, as it is written now, the plugin does not care at all that the 
object it manipulates are images (it cares that the object are 
constant/bounded size though). So would it be possible to extend/convert 
the image_transport plugin architecture, to a generic message_transport 
plugin architecture? I think sharedmem transfer would be particularly 
suitable for big point clouds...

I attach the targz of the package if someone wants to review it. It will 
NOT compile in a standard install, because of the "const" problem 
mentioned above. I include a patch to image_transport that removes the 
"const". Note that if you apply it, you also need to check the const in 
the other image_transport_plugins (2nd patch).


Dr. Cedric Pradalier

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