rcl: Common functionality for other ROS Client Libraries

rcl consists of functions and structs (pure C) organized into ROS concepts:

• Nodes
  • rcl/node.h
• Publisher
  • rcl/publisher.h
• Subscription
  • rcl/subscription.h
• Service Client
  • rcl/client.h
• Service Server
  • rcl/service.h
• Timer
  • rcl/timer.h

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

• Initialization and shutdown management (global for now)
  • rcl/rcl.h
• Wait sets for waiting on messages/service requests and responses/timers to be ready
  • rcl/wait.h
• Guard conditions for waking up wait sets asynchronously
  • rcl/guard_condition.h
• Functions for introspecting and getting notified of changes of the ROS graph
  • rcl/graph.h

Further still there are some useful abstractions and utilities:

• Allocator concept, which can used to control allocation in rcl_* functions
  • rcl/allocator.h
• Concept of ROS Time and access to steady and system wall time
  • rcl/time.h
• Error handling functionality (C style)
  • rcl/error_handling.h
• Macros
  • rcl/macros.h
• Return code types
  • rcl/types.h
• Macros for controlling symbol visibility on the library
  • rcl/visibility_control.h