[ros-users] Generic transport plugins and shared memory

[Dejan Pangercic]

Dear Cedric,

where are the packages
message_transport
sharedmem_transport
coming from? Are those yours?

cheers, D.
On Mon, May 10, 2010 at 11:09 PM, Cedric Pradalier
<cedric.pradalier at mavt.ethz.ch> wrote:
> Hi all,
>
> I'm not quite sure who will be interested by this message, but since we
> don't have (yet) our official ros repository, I'll send the info here.
> Please feel free to contact me or discuss on the list if you want more
> information.
>
> Given the long travel time coming back from ICRA, and my experience with
> the image_transport plugin architecture, I found that being only able to
> make transport_plugin and shared memory only for sensor_msgs::Image was
> a bit limiting.
>
> So I've adapted the image_transport framework using templates to make it
> generic, and integrated a generic shared memory transport into the
> framework. I've also ported the compressed and theora transport, but
> still keeping them specialised to Image.
>
> The resulting framework allow to create a starting set of plugins (raw
> and sharedmem) for (e.g) PointCloud using the following code:
>
> manifest.cpp:
> #include <pluginlib/class_list_macros.h>
> #include <message_transport/raw_publisher.h>
> #include <message_transport/raw_subscriber.h>
> #include <sharedmem_transport/sharedmem_publisher.h>
> #include <sharedmem_transport/sharedmem_subscriber.h>
> #include <sensor_msgs/PointCloud.h>
>
> // Raw class
> PLUGINLIB_REGISTER_CLASS(raw_pub,
>    message_transport::RawPublisher<sensor_msgs::PointCloud>,
>    message_transport::PublisherPlugin<sensor_msgs::PointCloud>)
> PLUGINLIB_REGISTER_CLASS(raw_sub,
>    message_transport::RawSubscriber<sensor_msgs::PointCloud>,
>    message_transport::SubscriberPlugin<sensor_msgs::PointCloud>)
>
> // Sharedmem class (the PointCloud message contains a header, which the
> publisher uses)
> PLUGINLIB_REGISTER_CLASS(sharedmem_pub,
>
> sharedmem_transport::SharedmemPublisherWithHeader<sensor_msgs::PointCloud>,
>
>    message_transport::PublisherPlugin<sensor_msgs::PointCloud>)
> PLUGINLIB_REGISTER_CLASS(sharedmem_sub,
>    sharedmem_transport::SharedmemSubscriber<sensor_msgs::PointCloud>,
>    message_transport::SubscriberPlugin<sensor_msgs::PointCloud>)
>
> Note that a specialised list_transport must be compiled for each message
> classes where plugins are developed:
> list_transport.cpp:
> #include <message_transport/list_transport.h>
> #include <sensor_msgs/PointCloud.h>
>
> using namespace message_transport;
>
> int main(int argc, char** argv)
> {
>    LIST_TRANSPORT("pointcloud_transport",sensor_msgs::PointCloud);
>
>    return 0;
> }
>
> As an instance, the plugin declaration for the compressed images starts
> with:
>
> class CompressedPublisher : public
>    message_transport::SimplePublisherPlugin<sensor_msgs::Image,
>        sensor_msgs::CompressedImage>
> { ...
>
> protected:
>  virtual void publish(const sensor_msgs::Image& message,
>          const message_transport::SimplePublisherPlugin<sensor_msgs::Image,
>                sensor_msgs::CompressedImage>::PublishFn& publish_fn)
> const ;
> };
>
>
> For the moment, my message_transport stack contains -- i.e. written and
> tested -- (indentation means dependency):
> message_transport_common
> ->sharedmem_transport
>  ->pointcloud_transport
>  ->imagem_transport
>    ->compressed_imagem_transport
>    ->theora_imagem_transport
>
> Other plugins are obviously possible and easy to write, to extend the
> library for image and pointcloud or for other types of message.
>
> HTH
>
> --
> Dr. Cedric Pradalier
> http://www.asl.ethz.ch/people/cedricp
>
> _______________________________________________
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>



-- 
MSc. Dejan Pangercic
PhD Student/Researcher
Intelligent Autonomous Systems Group
Technische Universität München
Telephone: +49 (89) 289-26908
E-Mail: dejan.pangercic at cs.tum.edu
WWW: http://ias.cs.tum.edu/people/pangercic