updated documentation (#332)

Signed-off-by: Jan Staschulat <[email protected]>
ros2 · Feb 7, 2023 · e63b644 · e63b644
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diff --git a/rclc_examples/CMakeLists.txt b/rclc_examples/CMakeLists.txt
@@ -33,8 +33,8 @@ include_directories(include)
 add_executable(example_executor src/example_executor.c)
 ament_target_dependencies(example_executor rcl rclc std_msgs)
 
-add_executable(example_executor_convenience src/example_executor_convenience.c)
-ament_target_dependencies(example_executor_convenience rcl rclc std_msgs)
+add_executable(example_executor_only_rcl src/example_executor_only_rcl.c)
+ament_target_dependencies(example_executor_only_rcl rcl rclc std_msgs)
 
 add_executable(example_executor_trigger src/example_executor_trigger.c)
 ament_target_dependencies(example_executor_trigger rcl rclc std_msgs)
@@ -69,7 +69,7 @@ ament_target_dependencies(example_short_timer_long_subscription rcl rclc std_msg
 
 install(TARGETS
   example_executor
-  example_executor_convenience
+  example_executor_only_rcl
   example_executor_trigger
   example_lifecycle_node
   example_service_node

diff --git a/rclc_examples/README.md b/rclc_examples/README.md
@@ -2,99 +2,46 @@ General information about this repository, including legal information, build in
 
 # The rclc_examples package
 
-The rclc_examples package provides examples for using the RCLC-Exector and convenience functions.
-- [example_executor.c](src/example_executor.c) provides the example for the RCLC-Executor. It creates one publisher and one subscriber and configures the RCLC-Executor accordingly. Then the spin_some() function is demonstrated.
-- [example_executor_convenience.c](src/example_executor_convenience.c) provides the example for the RCLC-Executor with the convenience functions from rclc. It creates one publisher and one subscriber and configures the RCLC-Executor accordingly. Then the spin_some() function is demonstrated.
+The rclc_examples package provides examples for using the RCLC-Exector and convenience functions for creating RCL objects like subscriptions and timers. 
+
+- [example_executor.c](src/example_executor.c) provides the example for the RCLC-Executor with the convenience functions from rclc. It creates one publisher and one subscriber and configures the RCLC-Executor accordingly.
 - [example_executor_trigger.c](src/example_executor_trigger.c) demonstrates the trigger condition of the RCLC-Executor.
 - [example_service_node.c](src/example_service_node.c) implements a service node with the RCLC-Executor.
 - [example_client_node.c](src/example_client_node.c) implements a client node with RCLC-Executor.
-- [example_short_timer_long_subscription.c](src/example_client_node.c) demo with high frequency timer and subscription with long processing time with one executor.
+- [example_executor_only_rcl.c](src/example_executor_only_rcl.c) provides the example for the RCLC-Executor. It creates one publisher and one subscriber and configures the RCLC-Executor using only the RCL API.
+- [example_short_timer_long_subscription.c](src/example_short_timer_long_subscription.c) demo with high frequency timer and subscription with long processing time with one executor.
+
 
 The reduction of code lines for configuring the necessary RCL objects for RCLC-Executor directly with RCL objects compared to using the convenience functions is about 24%:
 - example_executor.c: 92 LoC (lines 56-148)
 - example_executor_convenience.c: 70 LoC (line 17 + lines 57-126)
 
  counting only the lines of code in which the RCL objects are defined).
 
-## Example RCLC-Executor using RCL objects directly
+## Example RCLC-Executor
 **Step 1** Setup ROS 2 Workspace
 
 Open a terminal with ROS 2 workspace. Assuming that the ROS 2 installation resides in `/opt/ros/ROSDISTRO`, setup the ROS2 environment by:
 ```C
-~$ source /opt/ros/$ROSDISTRO/setup.bash
+~$ source /opt/ros/ROSDISTRO/setup.bash
 ```
 
 **Step 2** Build the package
-Download and build the the packages `rclc` and `rclc_examples` in a workspace (for example `ros2_ws`). Then source the workspace:
+Download and build the rclc repository in a workspace (for example `ros2_ws`). Then source the workspace:
 ```C
 ~/ros2_ws/$ colcon build --packages-up-to rclc_examples
 ~/ros2_ws/$ source ./install/local_setup.bash
 ```
-It should build these packages:
-- rcl_yaml_param_parser
-- rcl
-- rclc
-- rclc_examples
-
 
-**Step 3** Run the example executor.
+**Step 3** Run the example executor demo.
 
 The binary of the example is `example_executor`.
 
 ```C
-~/ros2_ws/$ ros2 run rclc_examples  example_executor
-```
-The publisher publishes the message `Hello World!`in `topic_0` at a rate of 1Hz and the subscriber prints out in the callback `Callback: I heard: Hello World!`.
-
-You should see the following output:
-
-```C
-Created timer with timeout 1000 ms.
-Created subscriber topic_0:
-Debug: number of DDS handles: 2
-Published message Hello World!
-Callback: I heard: Hello World!
-Published message Hello World!
-Callback: I heard: Hello World!
-Published message Hello World!
-Callback: I heard: Hello World!
-Published message Hello World!
-Callback: I heard: Hello World!
-Published message Hello World!
-Callback: I heard: Hello World!
-```
-
-
-
-## Example RCLC-Executor with convenience functions
-**Step 1** Setup ROS 2 Workspace
-
-Open a terminal with ROS 2 workspace. Assuming that the ROS 2 installation resides in `/opt/ros/eloquent`, setup
-the ROS2 environment by:
-```C
-~$ source /opt/ros/eloquent/setup.bash
+~/ros2_ws/$ ros2 run rclc_examples example_executor
 ```
 
-**Step 2** Build the package
-Download and build the the packages `rclc` and `rclc_examples` in a workspace (for example `ros2_ws`). Then source the workspace:
-```C
-~/ros2_ws/$ colcon build --packages-up-to rclc_examples
-~/ros2_ws/$ source ./install/local_setup.bash
-```
-It should build these packages:
-- rcl_yaml_param_parser
-- rcl
-- rclc
-- rclc_examples
-
-**Step 3** Run the example executor with the convenience functions from the package rclc.
-
-The binary of the example is `example_executor_convenience`.
-
-```C
-~/ros2_ws/$ ros2 run rclc_examples  example_executor_convenience
-```
-The same setup as in the example_executor, just using the RCLC convenience functions. You should see the exact same output:
+Example output:
 
 ```C
 Created timer with timeout 1000 ms.
@@ -196,18 +143,65 @@ $ ros2 run rclc_examples example_service_node
 INFO: rcl_wait timeout 10 ms
 Service request value: 24 + 42. Seq 1
 Received service response 24 + 42 = 66. Seq 1
-```C
+```
 
 window 2: start client node
 ```C
 ~$ ros2 run rclc_examples example_client_node
 Send service request 24 + 42. Seq 1
 INFO: rcl_wait timeout 10 ms
-```C
+```
 
 A request message is sent from the client node to the service node and answered.
 
+## Example RCLC-Executor using RCL objects directly
+**Step 1** Setup ROS 2 Workspace
+
+Open a terminal with ROS 2 workspace. Assuming that the ROS 2 installation resides in `/opt/ros/ROSDISTRO`, setup the ROS2 environment by:
+```C
+~$ source /opt/ros/$ROSDISTRO/setup.bash
+```
+
+**Step 2** Build the package
+Download the rclc repository in a workspace (for example `ros2_ws`). Then source the workspace:
+```C
+~/ros2_ws/$ colcon build --packages-up-to rclc_examples
+~/ros2_ws/$ source ./install/local_setup.bash
+```
+It should build these packages:
+- rcl_yaml_param_parser
+- rcl
+- rclc
+- rclc_examples
+
+
+**Step 3** Run the example executor.
+
+The binary of the example is `example_executor_only_rcl`.
+
+```C
+~/ros2_ws/$ ros2 run rclc_examples example_executor_only_rcl
+```
+The publisher publishes the message `Hello World!`in `topic_0` at a rate of 1Hz and the subscriber prints out in the callback `Callback: I heard: Hello World!`.
+
+You should see the following output:
+
+```C
+Created timer with timeout 1000 ms.
+Created subscriber topic_0:
+Debug: number of DDS handles: 2
+Published message Hello World!
+Callback: I heard: Hello World!
+Published message Hello World!
+Callback: I heard: Hello World!
+Published message Hello World!
+Callback: I heard: Hello World!
+Published message Hello World!
+Callback: I heard: Hello World!
+Published message Hello World!
+Callback: I heard: Hello World!
+```
 ## Example real-time concurrency slow timer and long subscription
 This example demonstrates what happens, if a high frequency timer (every 100ms) and
 a subscription with a long processing time is managed by one executor. This demo shows,
-that the timer events are dropped during the long processing time of the subscription and are also not caught-up when there would be sufficient time. 
+that the timer events are dropped during the long processing time of the subscription and are also not caught-up when there would be sufficient time. 
diff --git a/rclc_examples/src/example_executor.c b/rclc_examples/src/example_executor.c
@@ -14,9 +14,9 @@
 // limitations under the License.
 
 #include <stdio.h>
-
-#include <rclc/executor.h>
 #include <std_msgs/msg/string.h>
+#include <rclc/executor.h>
+#include <rclc/rclc.h>
 
 // these data structures for the publisher and subscriber are global, so that
 // they can be configured in main() and can be used in the corresponding callback.
@@ -56,31 +56,22 @@ void my_timer_callback(rcl_timer_t * timer, int64_t last_call_time)
 /******************** MAIN PROGRAM ****************************************/
 int main(int argc, const char * argv[])
 {
-  rcl_context_t context = rcl_get_zero_initialized_context();
-  rcl_init_options_t init_options = rcl_get_zero_initialized_init_options();
   rcl_allocator_t allocator = rcl_get_default_allocator();
+  rclc_support_t support;
   rcl_ret_t rc;
 
   // create init_options
-  rc = rcl_init_options_init(&init_options, allocator);
+  rc = rclc_support_init(&support, argc, argv, &allocator);
   if (rc != RCL_RET_OK) {
-    printf("Error rcl_init_options_init.\n");
-    return -1;
-  }
-
-  // create context
-  rc = rcl_init(argc, argv, &init_options, &context);
-  if (rc != RCL_RET_OK) {
-    printf("Error in rcl_init.\n");
+    printf("Error rclc_support_init.\n");
     return -1;
   }
 
   // create rcl_node
   rcl_node_t my_node = rcl_get_zero_initialized_node();
-  rcl_node_options_t node_ops = rcl_node_get_default_options();
-  rc = rcl_node_init(&my_node, "node_0", "executor_examples", &context, &node_ops);
+  rc = rclc_node_init_default(&my_node, "node_0", "executor_examples", &support);
   if (rc != RCL_RET_OK) {
-    printf("Error in rcl_node_init\n");
+    printf("Error in rclc_node_init_default\n");
     return -1;
   }
 
@@ -89,36 +80,27 @@ int main(int argc, const char * argv[])
   const char * topic_name = "topic_0";
   const rosidl_message_type_support_t * my_type_support =
     ROSIDL_GET_MSG_TYPE_SUPPORT(std_msgs, msg, String);
-  rcl_publisher_options_t pub_options = rcl_publisher_get_default_options();
-  rc = rcl_publisher_init(
+
+  rc = rclc_publisher_init_default(
     &my_pub,
     &my_node,
     my_type_support,
-    topic_name,
-    &pub_options);
+    topic_name);
   if (RCL_RET_OK != rc) {
-    printf("Error in rcl_publisher_init %s.\n", topic_name);
+    printf("Error in rclc_publisher_init_default %s.\n", topic_name);
     return -1;
   }
 
-  // create a timer, which will call the publisher every 'period' ms in the 'my_timer_callback'
-  rcl_clock_t clock;
-  rc = rcl_clock_init(RCL_STEADY_TIME, &clock, &allocator);
-  if (rc != RCL_RET_OK) {
-    printf("Error in rcl_clock_init.\n");
-    return -1;
-  }
+  // create a timer, which will call the publisher with period=`timer_timeout` ms in the 'my_timer_callback'
   rcl_timer_t my_timer = rcl_get_zero_initialized_timer();
   const unsigned int timer_timeout = 1000;
-  rc = rcl_timer_init(
+  rc = rclc_timer_init_default(
     &my_timer,
-    &clock,
-    &context,
+    &support,
     RCL_MS_TO_NS(timer_timeout),
-    my_timer_callback,
-    allocator);
+    my_timer_callback);
   if (rc != RCL_RET_OK) {
-    printf("Error in rcl_timer_init.\n");
+    printf("Error in rcl_timer_init_default.\n");
     return -1;
   } else {
     printf("Created timer with timeout %d ms.\n", timer_timeout);
@@ -134,16 +116,11 @@ int main(int argc, const char * argv[])
 
   // create subscription
   rcl_subscription_t my_sub = rcl_get_zero_initialized_subscription();
-  rcl_subscription_options_t my_subscription_options = rcl_subscription_get_default_options();
-
-
-  rc = rcl_subscription_init(
+  rc = rclc_subscription_init_default(
     &my_sub,
     &my_node,
     my_type_support,
-    topic_name,
-    &my_subscription_options);
-
+    topic_name);
   if (rc != RCL_RET_OK) {
     printf("Failed to create subscriber %s.\n", topic_name);
     return -1;
@@ -158,18 +135,17 @@ int main(int argc, const char * argv[])
   // Configuration of RCL Executor
   ////////////////////////////////////////////////////////////////////////////
   rclc_executor_t executor;
-
-  // compute total number of subsribers and timers
+  executor = rclc_executor_get_zero_initialized_executor();
+  // total number of handles = #subscriptions + #timers
+  //
+  // Note:
+  // If you need more than the default number of publisher/subscribers, etc., you 
+  // need to configure the micro-ROS middleware also!
+  // See documentation in the executor.h at the function rclc_executor_init() 
+  // for more details. 
   unsigned int num_handles = 1 + 1;
   printf("Debug: number of DDS handles: %u\n", num_handles);
-  rclc_executor_init(&executor, &context, num_handles, &allocator);
-
-  // set timeout for rcl_wait()
-  unsigned int rcl_wait_timeout = 1000;   // in ms
-  rc = rclc_executor_set_timeout(&executor, RCL_MS_TO_NS(rcl_wait_timeout));
-  if (rc != RCL_RET_OK) {
-    printf("Error in rclc_executor_set_timeout.");
-  }
+  rclc_executor_init(&executor, &support.context, num_handles, &allocator);
 
   // add subscription to executor
   rc = rclc_executor_add_subscription(
@@ -184,21 +160,16 @@ int main(int argc, const char * argv[])
     printf("Error in rclc_executor_add_timer.\n");
   }
 
-  // Optional prepare for avoiding allocations during spin
-  rclc_executor_prepare(&executor);
+  rclc_executor_spin(&executor);
 
-  for (unsigned int i = 0; i < 10; i++) {
-    // timeout specified in ns (here 1s)
-    rclc_executor_spin_some(&executor, 1000 * (1000 * 1000));
-  }
-
-  // clean up
+  // clean up (never called in this example)
   rc = rclc_executor_fini(&executor);
   rc += rcl_publisher_fini(&my_pub, &my_node);
   rc += rcl_timer_fini(&my_timer);
   rc += rcl_subscription_fini(&my_sub, &my_node);
   rc += rcl_node_fini(&my_node);
-  rc += rcl_init_options_fini(&init_options);
+  rc += rclc_support_fini(&support);
+
   std_msgs__msg__String__fini(&pub_msg);
   std_msgs__msg__String__fini(&sub_msg);