[cpp] Serialize ROS2 message for mcap outside of ROS2

[andrewwongagility]

Hello,
I'm trying to serialize a ROS2 message outside of ROS2 (using a custom middleware). I've provided some cpp toy code below that demonstrates what I'm trying to accomplish:

Writing data to mcap file (shown below)

1. Convert our custom image format to ROS2 raw image msg
2. Serialize the ROS2 image msg to a byte array (std::array<uint8_t>)

Reading data from mcap file (not shown below)

1. I'd also like to deserialize this message to use within our custom middleware

#include std_msgs/ImageRaw.cpp // ROS2 Image Raw msg

ImageFrame* frame;  // our custom image format

std_msgs::ImageRaw ros2_img; // ROS2 image format

// Fill out ROS 2 message struct with out custom image format
ros2_img.width = frame->width;
ros2_img.height = frame->height;
...
ros2_img.data = frame->data;

// TODO: perform serialization

Does foxglove provide any cpp libraries that serialize a ROS2 message? So far, I've looked into the serialization code in rclcpp, included in ROS2, but it appears that rclcpp has lots of dependencies, making it cumbersome to include as a library in our software. I would prefer to use a library instead of writing the serialization/deserialization myself, because I think it is easier to upgrade a library than rewrite custom code in the event that the ROS2 message definitions change in the future.

Thank you for your help!

[jtbandes]

The only implementation we currently provide is in TypeScript, in @foxglove/rosmsg2-serialization which uses @foxglove/cdr under the hood.

[andrewwongagility]

I apologize for the late reply. Thank you for your help; I've decided to use flatbuffers, since this is another workflow supported by Foxglove