ros2_medkit_serialization

Runtime JSON to ROS 2 message serialization library

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README

ros2_medkit_serialization

Runtime JSON ↔ ROS 2 message serialization library for the ros2_medkit gateway.

Overview

This package provides dynamic message serialization using dynmsg, enabling JSON ↔ ROS 2 message conversion at runtime without compile-time type dependencies. It eliminates CLI fallbacks in the gateway by providing native C++ APIs for all message operations.

Features

• JSON Serialization: Convert ROS 2 messages to/from JSON (via YAML bridge)

• CDR Serialization: Serialize JSON to CDR format for GenericPublisher and GenericClient

• CDR Deserialization: Deserialize CDR data from GenericSubscription to JSON

• Type Caching: Thread-safe caching of type introspection data with LRU eviction

• Service/Action Types: Helper functions for request/response/goal type derivation

• Schema Generation: Generate JSON schemas for ROS 2 message types

Dependencies

• dynmsg - OSRF dynamic message introspection library

• nlohmann_json - JSON library

• yaml_cpp_vendor - YAML library (for dynmsg compatibility)

• rclcpp - ROS 2 client library (for SerializedMessage)

Usage

#include "ros2_medkit_serialization/json_serializer.hpp"
#include "ros2_medkit_serialization/type_cache.hpp"

// Get type info (cached)
auto& cache = ros2_medkit_serialization::TypeCache::instance();
auto type_info = cache.get("std_msgs", "String");

// Create serializer
ros2_medkit_serialization::JsonSerializer serializer;

// Serialize JSON to CDR for GenericPublisher
nlohmann::json msg_json = {{"data", "Hello World"}};
auto serialized = serializer.serialize("std_msgs/msg/String", msg_json);
// Use with: generic_publisher->publish(serialized);

// Deserialize CDR to JSON from GenericSubscription
nlohmann::json result = serializer.deserialize("std_msgs/msg/String", serialized_msg);

// Convert in-memory message to JSON
nlohmann::json json = serializer.to_json(type_info, message_ptr);

// Generate schema for a type
nlohmann::json schema = serializer.get_schema("geometry_msgs/msg/Twist");

API Reference

JsonSerializer

Method	Description
serialize(type, json)	Serialize JSON to CDR SerializedMessage
deserialize(type, msg)	Deserialize CDR to JSON
to_json(type_info, ptr)	Convert in-memory message to JSON
from_json(type, json)	Create message from JSON
get_schema(type)	Get JSON schema for type
get_defaults(type)	Get default values as JSON
yaml_to_json(yaml)	Convert YAML node to JSON (static)

TypeCache

Method	Description
instance()	Get singleton instance
get(pkg, name)	Get cached type info
get(type_string)	Get cached type info from full type string
clear()	Clear all cached entries

Building

cd /path/to/ros2_medkit
colcon build --packages-select ros2_medkit_serialization

Testing

colcon test --packages-select ros2_medkit_serialization
colcon test-result --verbose

Design Documentation

See the design documentation for architecture details.

License

Apache-2.0