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Extract Context from rclcpp participant and add more details about context handles

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Christophe Bedard 2019-05-27 16:34:25 +02:00
parent 19f64b4658
commit 5d3ba8720e
1 changed files with 9 additions and 5 deletions
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14
doc/design_ros_2.md
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@ -16,7 +16,7 @@ This document will (for now) mainly discuss `rcl` and `rclcpp`, but `rclpy` shou
### Process creation
In the call to `rclcpp::init(argc, argv)`, an `rclcpp::Context` object is created and CLI arguments are parsed. Much of the work is actually done by `rcl` through a call to `rcl_init()`.
In the call to `rclcpp::init()`, a process-specific `rclcpp::Context` object is fetched and CLI arguments are parsed. Much of the work is actually done by `rcl` through a call to `rcl_init()`. This call processes the `rcl_context_t` handle, which is wrapped by the `Context` object. Also, inside this call, `rcl` calls `rmw_init()` to process the `rmw` context (`rmw_context_t`) as well. This `rmw` handle is itself part of the `rcl_context_t` handle.
This has to be done once per process, and usually at the very beginning. The components that are then instanciated share this context.
@ -24,15 +24,19 @@ This has to be done once per process, and usually at the very beginning. The com
sequenceDiagram
participant process
participant rclcpp
participant Context
participant rcl
participant rmw
participant tracetools
process->>rclcpp: rclcpp::init()
Note over rclcpp: allocates rclcpp::Context object
rclcpp->>rcl: rcl_init(out context)
Note over rcl: validates & processes context object
process->>rclcpp: rclcpp::init(argc, argv)
Note over rclcpp: fetches process-specific Context object
rclcpp->>Context: init(argc, argv)
Note over Context: allocates rcl_context_t handle
Context->>rcl: rcl_init(out rcl_context_t)
Note over rcl: validates & processes rcl_context_t handle
rcl->>rmw: rmw_init(out rmw_context_t)
Note over rmw: validates & processes rmw_context_t handle
rcl->>tracetools: TP(rcl_init, &context)
```