fix: to #590 flip buffer before read ops

Signed-off-by: Li Zhanhui <[email protected]>

store/src/main/java/com/automq/rocketmq/store/queue/DefaultLogicQueueStateMachine.java

@@ -673,6 +673,8 @@ public ByteBuffer getAckBitmapBuffer() throws IOException {
             int length = bitmap.serializedSizeInBytes();
             ByteBuffer buffer = ByteBuffer.allocate(length);
             bitmap.serialize(buffer);
+            // Flip buffer to prepare read
+            buffer.flip();
             return buffer;
         }
     }

store/src/test/java/com/automq/rocketmq/store/queue/AckCommitterTest.java

@@ -0,0 +1,36 @@
+/*
+ * 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.
+ */
+
+package com.automq.rocketmq.store.queue;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class AckCommitterTest {
+
+    @Test
+    public void testGetAckBitmapBuffer() throws IOException {
+        DefaultLogicQueueStateMachine.AckCommitter ackCommitter = new DefaultLogicQueueStateMachine.AckCommitter(100,
+            System.out::println);
+        ackCommitter.commitAck(102);
+        ByteBuffer buffer = ackCommitter.getAckBitmapBuffer();
+        Assertions.assertEquals(0, buffer.position());
+        Assertions.assertTrue(buffer.limit() > 0);
+    }
+}