Add function rcl_event_is_valid

rcl/include/rcl/event.h

@@ -170,6 +170,28 @@ RCL_WARN_UNUSED
 rmw_event_t *
 rcl_event_get_rmw_handle(const rcl_event_t * event);
 
+/// Check that the event is valid.
+/**
+ * The bool returned is `false` if `event` is invalid.
+ * The bool returned is `true` otherwise.
+ * In the case where `false` is to be returned, an error message is set.
+ * This function cannot fail.
+ *
+ * <hr>
+ * Attribute          | Adherence
+ * ------------------ | -------------
+ * Allocates Memory   | No
+ * Thread-Safe        | No
+ * Uses Atomics       | No
+ * Lock-Free          | Yes
+ *
+ * \param[in] event pointer to the rcl event
+ * \return `true` if `event` is valid, otherwise `false`
+ */
+RCL_PUBLIC
+bool
+rcl_event_is_valid(const rcl_event_t * event);
+
 #ifdef __cplusplus
 }
 #endif

rcl/src/rcl/event.c

@@ -190,6 +190,20 @@ rcl_event_get_rmw_handle(const rcl_event_t * event)
   }
 }
 
+bool
+rcl_event_is_valid(const rcl_event_t * event)
+{
+  RCL_CHECK_FOR_NULL_WITH_MSG(event, "event pointer is invalid", return false);
+  RCL_CHECK_FOR_NULL_WITH_MSG(event->impl, "event's implementation is invalid", return false);
+  /*
+  if (event->impl->rmw_handle.event_type == RMW_EVENT_INVALID) {
+    RCUTILS_SET_ERROR_MSG("event's implementation not init");
+    return false;
+  }
+  */
+  return true;
+}
+
 #ifdef __cplusplus
 }
 #endif

rcl/test/rcl/test_events.cpp

@@ -730,6 +730,27 @@ TEST_F(TestEventFixture, test_bad_get_handle)
   EXPECT_EQ(NULL, rcl_event_get_rmw_handle(NULL));
 }
 
+/*
+ * Test cases for the event_is_valid function
+ */
+TEST_F(TestEventFixture, test_event_is_valid)
+{
+  EXPECT_FALSE(rcl_event_is_valid(nullptr));
+
+  setup_publisher_subscriber(default_qos_profile, default_qos_profile);
+  rcl_event_t publisher_event_test = rcl_get_zero_initialized_event();
+  EXPECT_FALSE(rcl_event_is_valid(&publisher_event_test));
+
+  rcl_ret_t ret = rcl_publisher_event_init(
+    &publisher_event_test, &publisher, RCL_PUBLISHER_OFFERED_DEADLINE_MISSED);
+  ASSERT_EQ(ret, RCL_RET_OK) << rcl_get_error_string().str;
+  EXPECT_TRUE(rcl_event_is_valid(&publisher_event_test));
+
+  ret = rcl_event_fini(&publisher_event_test);
+  EXPECT_EQ(ret, RCL_RET_OK) << rcl_get_error_string().str;
+  tear_down_publisher_subscriber();
+}
+
 static
 std::array<TestIncompatibleQosEventParams, 5>
 get_test_pubsub_incompatible_qos_inputs()