Add rmw_publisher_wait_for_all_acked support (#296)

Signed-off-by: Barry Xu <[email protected]>

rmw/include/rmw/rmw.h

@@ -806,6 +806,51 @@ RMW_WARN_UNUSED
 rmw_ret_t
 rmw_publisher_assert_liveliness(const rmw_publisher_t * publisher);
 
+/// Wait until all published message data is acknowledged or until the specified timeout elapses.
+/**
+ * This function waits until all published message data were acknowledged by peer node or timeout.
+ *
+ * This function only works effectively while QOS profile of publisher is set to RELIABLE.
+ * Otherwise this function will immediately return RMW_RET_OK.
+ *
+ * <hr>
+ * Attribute          | Adherence
+ * ------------------ | -------------
+ * Allocates Memory   | Maybe [1]
+ * Thread-Safe        | Yes
+ * Uses Atomics       | Maybe [1]
+ * Lock-Free          | Maybe [1]
+ * <i>[1] rmw implementation defined, check the implementation documentation</i>
+ *
+ * \par Runtime behavior
+ *   Waiting for all acknowledgments is synchronous operation.
+ *   So the calling thread is blocked until all published message data is acknowledged or specified
+ *   duration elapses.
+ *
+ * \par Thread-Safety
+ *   Publishers are thread-safe objects, and so are all operations on them except for finalization.
+ *   Therefore, it is safe to call this function using the same publisher concurrently.
+ *
+ * \pre Given `publisher` must be a valid publisher, as returned by rmw_create_publisher().
+ *
+ * \param[in] publisher handle to the publisher that needs to wait for all acked.
+ * \param[in] wait_timeout represents the maximum amount of time to wait for all published message
+ *   data were acknowledged.
+ * \return `RMW_RET_OK` if successful, or
+ * \return `RMW_RET_TIMEOUT` if wait timed out, or
+ * \return `RMW_RET_INVALID_ARGUMENT` if `publisher` is `NULL`, or
+ * \return `RMW_RET_INCORRECT_RMW_IMPLEMENTATION` if the `publisher` implementation
+ *   identifier does not match this implementation, or
+ * \return `RMW_RET_ERROR` if an unspecified error occurs, or
+ * \return `RMW_RET_UNSUPPORTED` if the rmw implementation is unimplemented.
+ */
+RMW_PUBLIC
+RMW_WARN_UNUSED
+rmw_ret_t
+rmw_publisher_wait_for_all_acked(
+  const rmw_publisher_t * publisher,
+  rmw_time_t wait_timeout);
+
 /// Serialize a ROS message into a rmw_serialized_message_t.
 /**
  * The ROS message is serialized into a byte stream contained within the