refactor: add GUARD macro for RAII with C pointers and deleters

Author: BewareMyPower

include/snctl-cpp/raii_helper.h

@@ -0,0 +1,24 @@
+/**
+ * Copyright 2025 Yunze Xu
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+// Call the deleter on ptr when it goes out of scope
+//   ptr must be a pointer type T*
+//   deleter must be a function pointer type void(*)(T*)
+#define GUARD(ptr, deleter)                                                    \
+  std::unique_ptr<std::remove_reference_t<decltype(*(ptr))>,                   \
+                  decltype((deleter))>                                         \
+      ptr##_guard{ptr, deleter};

include/snctl-cpp/topics/create_topic.h

@@ -15,6 +15,7 @@
  */
 #pragma once
 
+#include "snctl-cpp/raii_helper.h"
 #include "snctl-cpp/rk_event_wrapper.h"
 #include <array>
 #include <iostream>
@@ -33,9 +34,7 @@ inline void create_topic(rd_kafka_t *rk, rd_kafka_queue_t *rkqu,
     throw std::runtime_error("Failed to create topic: " +
                              std::string(errstr.data()));
   }
-  std::unique_ptr<std::remove_reference_t<decltype(*rk_topic)>,
-                  decltype(&rd_kafka_NewTopic_destroy)>
-      rk_topic_guard{rk_topic, &rd_kafka_NewTopic_destroy};
+  GUARD(rk_topic, rd_kafka_NewTopic_destroy);
 
   rd_kafka_CreateTopics(rk, &rk_topic, 1, nullptr, rkqu);
 

include/snctl-cpp/topics/delete_topic.h

@@ -15,6 +15,7 @@
  */
 #pragma once
 
+#include "snctl-cpp/raii_helper.h"
 #include "snctl-cpp/rk_event_wrapper.h"
 #include <iostream>
 #include <librdkafka/rdkafka.h>
@@ -26,9 +27,7 @@
 inline void delete_topic(rd_kafka_t *rk, rd_kafka_queue_t *rkqu,
                          const std::string &topic) {
   auto rk_topic = rd_kafka_DeleteTopic_new(topic.c_str());
-  std::unique_ptr<std::remove_reference_t<decltype(*rk_topic)>,
-                  decltype(&rd_kafka_DeleteTopic_destroy)>
-      rk_topic_guard{rk_topic, &rd_kafka_DeleteTopic_destroy};
+  GUARD(rk_topic, rd_kafka_DeleteTopic_destroy);
 
   rd_kafka_DeleteTopics(rk, &rk_topic, 1, nullptr, rkqu);
 

include/snctl-cpp/topics/describe_topic.h

@@ -15,6 +15,7 @@
  */
 #pragma once
 
+#include "snctl-cpp/raii_helper.h"
 #include "snctl-cpp/rk_event_wrapper.h"
 #include <iostream>
 #include <librdkafka/rdkafka.h>
@@ -25,9 +26,7 @@ inline void describe_topic(rd_kafka_t *rk, rd_kafka_queue_t *rkqu,
                            const std::string &topic) {
   const char *topics[] = {topic.c_str()};
   auto topic_names = rd_kafka_TopicCollection_of_topic_names(topics, 1);
-  std::unique_ptr<std::remove_reference_t<decltype(*topic_names)>,
-                  decltype(&rd_kafka_TopicCollection_destroy)>
-      topic_names_guard{topic_names, &rd_kafka_TopicCollection_destroy};
+  GUARD(topic_names, rd_kafka_TopicCollection_destroy);
 
   rd_kafka_DescribeTopics(rk, topic_names, nullptr, rkqu);
 

src/main.cc

@@ -29,6 +29,7 @@
 #include <type_traits>
 #include <vector>
 
+#include "snctl-cpp/raii_helper.h"
 #include "snctl-cpp/topics.h"
 
 int main(int argc, char *argv[]) {
@@ -137,14 +138,10 @@ int main(int argc, char *argv[]) {
   if (!rk) {
     fail("create producer");
   }
-  std::unique_ptr<std::remove_reference_t<decltype(*rk)>,
-                  decltype(&rd_kafka_destroy)>
-      rk_guard{rk, &rd_kafka_destroy};
+  GUARD(rk, rd_kafka_destroy);
 
   auto rkqu = rd_kafka_queue_new(rk);
-  std::unique_ptr<std::remove_reference_t<decltype(*rkqu)>,
-                  decltype(&rd_kafka_queue_destroy)>
-      rkque_guard{rkqu, &rd_kafka_queue_destroy};
+  GUARD(rkqu, rd_kafka_queue_destroy);
 
   if (program.is_subcommand_used(topics.handle())) {
     return topics.run(rk, rkqu) ? 0 : 1;