Add function to get publisher actual qos settings (#169)

* Added rmw_publisher_get_actual_qos function

Signed-off-by: ivanpauno <[email protected]>

* Add RMW_QOS_POLICY_*_UNKNOWN enum value

Signed-off-by: ivanpauno <[email protected]>

Author: ivanpauno

rmw/include/rmw/rmw.h

@@ -251,6 +251,32 @@ rmw_publisher_count_matched_subscriptions(
   const rmw_publisher_t * publisher,
   size_t * subscription_count);
 
+/// Retrieve the actual qos settings of the publisher.
+/**
+ * Query the underlying middleware to determine the qos settings
+ * of the publisher.
+ * The actual configuration applied when using RMW_*_SYSTEM_DEFAULT
+ * can only be resolved after the creation of the publisher, and it
+ * depends on the underlying rmw implementation.
+ * If the underlying setting in use can't be represented in ROS terms,
+ * it will be set to RMW_*_UNKNOWN.
+ * The value of avoid_ros_namespace_conventions field is not resolved
+ * with this function. The rcl function rcl_publisher_get_actual_qos
+ * resolves it.
+ *
+ * \param[in] publisher the publisher object to inspect
+ * \param[out] qos the actual qos settings
+ * \return `RMW_RET_OK` if successful, or
+ * \return `RMW_RET_INVALID_ARGUMENT` if either argument is null, or
+ * \return `RMW_RET_ERROR` if an unexpected error occurs.
+ */
+RMW_PUBLIC
+RMW_WARN_UNUSED
+rmw_ret_t
+rmw_publisher_get_actual_qos(
+  const rmw_publisher_t * publisher,
+  rmw_qos_profile_t * qos);
+
 /// Publish an already serialized message.
 /**
  * The publisher must already be registered with the correct message type

rmw/include/rmw/types.h

@@ -175,21 +175,24 @@ enum RMW_PUBLIC_TYPE rmw_qos_reliability_policy_t
 {
   RMW_QOS_POLICY_RELIABILITY_SYSTEM_DEFAULT,
   RMW_QOS_POLICY_RELIABILITY_RELIABLE,
-  RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT
+  RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT,
+  RMW_QOS_POLICY_RELIABILITY_UNKNOWN
 };
 
 enum RMW_PUBLIC_TYPE rmw_qos_history_policy_t
 {
   RMW_QOS_POLICY_HISTORY_SYSTEM_DEFAULT,
   RMW_QOS_POLICY_HISTORY_KEEP_LAST,
-  RMW_QOS_POLICY_HISTORY_KEEP_ALL
+  RMW_QOS_POLICY_HISTORY_KEEP_ALL,
+  RMW_QOS_POLICY_HISTORY_UNKNOWN
 };
 
 enum RMW_PUBLIC_TYPE rmw_qos_durability_policy_t
 {
   RMW_QOS_POLICY_DURABILITY_SYSTEM_DEFAULT,
   RMW_QOS_POLICY_DURABILITY_TRANSIENT_LOCAL,
-  RMW_QOS_POLICY_DURABILITY_VOLATILE
+  RMW_QOS_POLICY_DURABILITY_VOLATILE,
+  RMW_QOS_POLICY_DURABILITY_UNKNOWN
 };
 
 /// ROS MiddleWare quality of service profile.