feat: Support message copy for C client.

include/pulsar/c/message.h

@@ -33,6 +33,15 @@ typedef struct _pulsar_message pulsar_message_t;
 typedef struct _pulsar_message_id pulsar_message_id_t;
 
 PULSAR_PUBLIC pulsar_message_t *pulsar_message_create();
+/**
+ * Copy the contents of one pulsar_message_t object to another.
+ *
+ * Note: This method is a shallow copy, which will copy the pulsar::Message.
+ *
+ * @param from  A pointer to the pulsar_message_t object that you want to copy from
+ * @param to  A pointer to the pulsar_message_t object that you want to copy to
+ */
+PULSAR_PUBLIC void pulsar_message_copy(const pulsar_message_t *from, pulsar_message_t *to);
 PULSAR_PUBLIC void pulsar_message_free(pulsar_message_t *message);
 
 /// Builder

lib/c/c_Message.cc

@@ -23,6 +23,11 @@
 
 pulsar_message_t *pulsar_message_create() { return new pulsar_message_t; }
 
+void pulsar_message_copy(const pulsar_message_t *from, pulsar_message_t *to) {
+    to->builder = from->builder;
+    to->message = from->message;
+}
+
 void pulsar_message_free(pulsar_message_t *message) { delete message; }
 
 void pulsar_message_set_content(pulsar_message_t *message, const void *data, size_t size) {

tests/c/c_MessageTest.cc

@@ -0,0 +1,34 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+#include <gtest/gtest.h>
+#include <lib/c/c_structs.h>
+#include <pulsar/c/message.h>
+
+TEST(c_MessageTest, MessageCopy) {
+    pulsar_message_t *from = pulsar_message_create();
+    pulsar_message_set_content(from, "hello", 5);
+    from->message = from->builder.build();
+    pulsar_message_t *to = pulsar_message_create();
+
+    pulsar_message_copy(from, to);
+    ASSERT_STREQ((const char *)pulsar_message_get_data(to), (const char *)pulsar_message_get_data(from));
+
+    pulsar_message_free(from);
+    pulsar_message_free(to);
+}