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cx_ros_msgs_plugin package from clips_executive repo

clips_executive cx_bringup cx_clips_env_manager cx_msgs cx_plugin cx_ament_index_plugin cx_config_plugin cx_example_plugin cx_executive_plugin cx_file_load_plugin cx_protobuf_plugin cx_ros_msgs_plugin cx_ros_param_plugin cx_tf2_pose_tracker_plugin cx_ros_comm_gen cx_tutorial_agents cx_utils

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Package Summary

Tags	No category tags.
Version	0.1.2
License	Apache-2.0
Build type	AMENT_CMAKE
Use	RECOMMENDED

Repository Summary

Description
Checkout URI	https://github.com/carologistics/clips_executive.git
VCS Type	git
VCS Version	master
Last Updated	2025-07-18
Dev Status	MAINTAINED
Released	RELEASED
Tags	No category tags.
Contributing	Help Wanted (-) Good First Issues (-) Pull Requests to Review (-)

Package Description

CLIPS plugin for using generic ROS topics via introspection API

Additional Links

No additional links.

Maintainers

Tarik Viehmann

Authors

No additional authors.

cx_plugins/ros_msgs_plugin/README.md

cx_ros_msgs_plugin

This package offers the `cx::RosMsgsPlugin’ that provides functions to interface with ros topics of any type. It makes use of the ROS introspection API to create generic publishers and subscriptions on-the-fly and to serialize and deserialize ROS messages.

Usage

Register this plugin with the plugin manager. It requires no additional configuration, an example setup is shown below:

clips_manager:
  ros__parameters:
    environments: ["main"]
    main:
      plugins: ["ros_msgs"]

    ros_msgs:
      plugin: "cx::RosMsgsPlugin"

CLIPS Features

This plugin defines deftemplates and user-defined functions that are described below.

Deftemplates

; Asserted by the create-subscription function.
; Retracted by the destroy-subscription function.
(deftemplate ros-msgs-subscription
  (slot topic (type STRING)) ; example: "/cx_string_in"
  (slot type (type STRING))  ; example: "std_msgs/msg/String"
)

; Asserted by the ros-msgs-create-publisher function.
; Retracted by the respective ros-msgs-destroy-publisher function.
(deftemplate-ros-msgs-publisher
  (slot topic (type STRING)) ; example: "/cx_string_out"
  (slot type (type STRING))  ; example: "std_msgs/msg/String"
)

; Asserted by the callback of a subscriber whenever a message arrives.
; Process the message and then call ros-msgs-destroy-msgs before retracting!
(deftemplate ros-msgs-message
  (slot topic (type STRING)) ; example          : "/cx_string_in"
  (slot msg-ptr (type EXTERNAL-ADDRESS)) example: <Pointer-C-0x7f1550001d20>
)

Functions

; Create and destroy publishers and subscribers.
(ros-msgs-create-publisher ?topic-name ?msg-type)    ; example args: "/cx_string_out" "std_msgs/msg/String"
(ros-msgs-destroy-publisher ?topic-name)             ; example args: "/cx_string_out"
(ros-msgs-create-subscription ?topic-name ?msg-type) ; example args: "/cx_string_in" "std_msgs/msg/String"
(ros-msgs-destroy-subscription ?topic-name)          ; example args: "/cx_string_in"

; Publish a given message over a topic.
; Requires the publisher to be created first using create-publisher.
(ros-msgs-publish ?msg-ptr ?topic-name)

; Create a message and return a pointer to it
(bind ?msg-ptr (ros-msgs-create-message ?msg-type)) ; example args: "std_msgs/msg/String"
                                                    ; example ret: <Pointer-C-0x7f1550001d20>

; Destroy a message, call this after publishing a message or processing an incoming message to prevent it from staying in memory.
(ros-msgs-destroy-message ?msg-ptr) ; example args: <Pointer-C-0x7f1550001d20>

; Populate the field of a message.
; If the field is a message, then pass a pointer to that message obtained from ros-msgs-create-message.
(ros-msgs-set-field ?msg-ptr ?field-name ?field-value) ; example args: <Pointer-C-0x7f1550001d20> "data" "Hello World"

; Retrieve a field of a message.
; If the field is a message, then a pointer is returned that can be further inspected by passing it to ros-msgs-get-field.
(ros-msgs-get-field ?msg-ptr ?field-name)

Object Lifetimes and CLIPS

Since clips stores objects via void pointers, dynamic object lifetime management via std::shared_ptr does not work direcly from within CLIPS. Instead, object lifetimes need to be managed more explicitly through the usage of create and destroy functions.

It is advised to clean up all objects as soon as they are not needed anymore in order to free up memory.

Note that when processing nested messages, the message obtained via ros-msgs-get-field is not allocating new memory, but rather points to the memory of the parent message. Calling ros-msgs-destroy-message is not necessary, as sub-messages retrieved via ros-msgs-get-field only hold a shallow reference and are cleaned up when the parent message is destroyed. Calling it anyways, will only invalidate this shallow reference.

When creating a new message via ros-msgs-create-message, new memory is allocated. When using ros-msgs-set-field to set a nested message, dynamic memory from the sub-message is moved to the parent message, hence the nested message loses all dynamicly allocated data (e.g., unbound arrays, strings). See the example below:

(bind ?new-msg (ros-msgs-create-message "geometry_msgs/msg/Twist"))
(bind ?sub-msg (ros-msgs-create-message "geometry_msgs/msg/Vector3"))
(ros-msgs-set-field ?sub-msg "x" 5.5)
(ros-msgs-set-field ?new-msg "linear" ?sub-msg)
; now all dynamicly allocated members of ?sub-msg are reset,
; as they are moved to the parent message.

In particular, obtaining a nested message from one message ?source and setting it as a member to another message ?sink will cause ?source to lose all dynamic data within it’s sub-message, as the sub-message obtained is actually pointing to memory within ?source:

```lisp (bind ?source (ros-msgs-create-message “geometry_msgs/msg/Twist”)) (bind ?sub-msg (ros-msgs-create-message “geometry_msgs/msg/Vector3”)) (ros-msgs-set-field ?sub-msg “x” 5.5) (ros-msgs-set-field ?source “linear” ?sub-msg) (bind ?sink (ros-msgs-create-message “geometry_msgs/msg/Twist”))

File truncated at 100 lines see the full file

CHANGELOG

Changelog for package cx_ros_msgs_plugin

0.1.2 (2025-07-16)

0.1.1 (2025-07-11)

project: prepare for first ros2 release
Contributors: Tarik Viehmann

Package Dependencies

Deps	Name
	ament_cmake
	rclcpp
	pluginlib
	cx_plugin
	cx_utils
	clips_vendor
	rosidl_typesupport_cpp
	rosidl_typesupport_introspection_cpp
	rcutils

System Dependencies

Name
libicu-dev

Dependant Packages

Name	Deps
clips_executive
cx_bringup

Launch files

No launch files found

Messages

No message files found.

Services

No service files found

Plugins

cx_plugin

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