Add continuos serialization

Acuadros95 · Acuadros95 · commit d9df00b9b3af · 2021-08-27T09:45:33.000+02:00
diff --git a/_docs/tutorials/programming_rcl_rclc/executor/executor.md b/_docs/tutorials/programming_rcl_rclc/executor/executor.md
@@ -53,7 +53,6 @@ void timer_callback(rcl_timer_t * timer, int64_t last_call_time)
 
 During the callback the timer can be canceled or have its period and/or callback modified using the passed pointer. Check [rcl/timer.h](https://github.com/ros2/rcl/blob/galactic/rcl/include/rcl/timer.h) for details.
 
-
 ### Cleaning Up
 
 To destroy an initialized timer:
diff --git a/_docs/tutorials/programming_rcl_rclc/micro-ROS/micro-ROS.md b/_docs/tutorials/programming_rcl_rclc/micro-ROS/micro-ROS.md
@@ -168,9 +168,62 @@ else
 
 ## Continous serialization
 
--```c
-void rmw_uros_set_continous_serialization_callbacks(
-rmw_publisher_t * publisher,
-rmw_uros_continous_serialization_size size_cb,
-rmw_uros_continous_serialization serialization_cb);
-```
+This utility allows the client to serialize and send data up to a customized size. The user can set the topic lenght and then serialize the data within the publish process. An example can be found on [`micro-ROS-demos/rclc/ping_uros_agent`](https://github.com/micro-ROS/micro-ROS-demos/blob/galactic/rclc/ping_uros_agent/main.c), where fragments from an image are requested and serialized on the spot.
+
+The user needs to define two callbacks, then set them on the `rmw`. It is recommended to clean the callbacks after the publication, to avoid interferences with other topics on the same process:
+
+```c
+// Set serialization callbacks
+rmw_uros_set_continous_serialization_callbacks(size_cb, serialization_cb);
+
+// Publish message
+rcl_publish(...);
+
+// Clean callbacks
+rmw_uros_set_continous_serialization_callbacks(NULL, NULL);
+```
+
+- Size callback:
+
+This callback will pass a pointer with the calculated message size. The user is responsible of increase this size to the expected value:
+
+```c
+// Function prototype:
+void (* rmw_uros_continous_serialization_size)(uint32_t * topic_length);
+
+// Implementation example:
+void size_cb(uint32_t * topic_length){
+    // Increase message size
+    *topic_length += ucdr_alignment(*topic_length, sizeof(uint32_t)) + sizeof(uint32_t);
+    *topic_length += IMAGE_BYTES;
+}
+```
+
+- Serialize callback:
+
+This callback gives the user the message buffer to be completed. The user is responsible of serialize the data up to the lenght established on the size callback:
+
+```c
+// Function prototype:
+void (* rmw_uros_continous_serialization)(ucdrBuffer * ucdr);
+
+// Implementation example:
+void serialization_cb(ucdrBuffer * ucdr){
+    size_t len = 0;
+    micro_ros_fragment_t fragment;
+
+    // Serialize array size
+    ucdr_serialize_uint32_t(ucdr, IMAGE_BYTES); 
+
+    while(len < IMAGE_BYTES){
+      // Wait for new image "fragment"
+      ...
+
+      // Serialize data fragment
+      ucdr_serialize_array_uint8_t(ucdr, fragment.data, fragment.len);
+      len += fragment.len;
+    }
+}
+```
+
+*Note: When the callback ends, the message will be published.*
diff --git a/_docs/tutorials/programming_rcl_rclc/pub_sub/pub_sub.md b/_docs/tutorials/programming_rcl_rclc/pub_sub/pub_sub.md
@@ -199,7 +199,7 @@ The function will have the message as its only argument, containing the values s
 // Function prototype:
 void (* rclc_subscription_callback_t)(const void *);
 
-// Example:
+// Implementation example:
 void subscription_callback(const void * msgin)
 {
   // Cast received message to used type
@@ -210,7 +210,6 @@ void subscription_callback(const void * msgin)
 }
 ```
 
-
 Once the subscriber and the executor are initialized, the subscriber callback must be added to the executor to receive incoming publications once its spinning:
 
 ```c
@@ -225,6 +224,7 @@ rcl_ret_t rc = rclc_executor_add_subscription(
 if (RCL_RET_OK != rc) {
   ...  // Handle error
   return -1;
+}
 
 // Spin executor to receive messages
 rclc_executor_spin(&executor);
diff --git a/_docs/tutorials/programming_rcl_rclc/qos/QoS.md b/_docs/tutorials/programming_rcl_rclc/qos/QoS.md
@@ -3,9 +3,6 @@ title: Quality of service
 permalink: /docs/tutorials/programming_rcl_rclc/qos/
 ---
 
-// Add benchmark results for Throughput and RTT to compare both modes?
-// Explain custom QoS options
-
 - [Reliable QoS](#reliable-qos)
 - [Best Effort](#best-effort)
 - [Custom QoS configuration](#custom-qos-configuration)
diff --git a/_docs/tutorials/programming_rcl_rclc/service/services.md b/_docs/tutorials/programming_rcl_rclc/service/services.md
@@ -113,7 +113,7 @@ The client request message will contain two integers `a` and `b`, and expects th
 // Function prototype:
 void (* rclc_service_callback_t)(const void *, void *);
 
-// Example:
+// Implementation example:
 void service_callback(const void * request_msg, void * response_msg){
   // Cast messages to expected types
   example_interfaces__srv__AddTwoInts_Request * req_in =
@@ -233,7 +233,7 @@ It is necessary to cast the response message to the expected type. Example:
 // Function prototype:
 void (* rclc_client_callback_t)(const void *);
 
-// Example:
+// Implementation example:
 void client_callback(const void * response_msg){
   // Cast response message to expected type
   example_interfaces__srv__AddTwoInts_Response * msgin =
