rcl: Common functionality ROS actions

rcl_action provides a pure C implementation of the ROS concept of an action. It builds on top of the implementation of topics and services in rcl.

rcl_action consists of functions and structs for the following ROS action entities:

• Action client
  • rcl_action/action_client.h
• Action server
  • rcl_action/action_server.h
• Goal handle
  • rcl_action/goal_handle.h
• Goal state machine
  • rcl_action/goal_state_machine.h

It also has some machinery that is necessary to wait on and act on these entities:

• Wait sets for waiting on actions clients and action servers to be ready
  • rcl_action/wait.h

Some useful abstractions and utilities:

• Return codes and other types
  • rcl_action/types.h