is there any function to convert sensor_msg::pointcloud2 to velodyne_pointcloud::PointXYZIR? I want to get the ring number

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I am getting the data as a sensor_msg::pointcloud2 and then i convert them in to pcl::pointcloud to do clustering and ground plane removal and other processing. Now i am in need to access the ring number. what i thought is it would be easier if i can convert the sensor_msg::pointcloud2 to velodyne_pointcloud::PointXYZIR. which gives me the ring values of the corresponding points in the pcl::pointcloud. but i could not find any functions doing this conversion