Fix CRC calculation for heap buffers

Fixes #16

Author: acogoluegnes

src/main/java/com/rabbitmq/stream/impl/JdkChunkChecksum.java

@@ -39,7 +39,8 @@ class JdkChunkChecksum implements ChunkChecksum {
   public void checksum(ByteBuf byteBuf, long dataLength, long expected) {
     Checksum checksum = checksumSupplier.get();
     if (byteBuf.hasArray()) {
-      checksum.update(byteBuf.array(), byteBuf.readerIndex(), byteBuf.readableBytes());
+      checksum.update(
+          byteBuf.array(), byteBuf.arrayOffset() + byteBuf.readerIndex(), byteBuf.readableBytes());
     } else {
       byteBuf.forEachByte(
           byteBuf.readerIndex(), byteBuf.readableBytes(), new UpdateProcessor(checksum));

src/test/java/com/rabbitmq/stream/impl/ClientTest.java

@@ -32,6 +32,8 @@
 import com.rabbitmq.stream.impl.Client.ClientParameters;
 import com.rabbitmq.stream.impl.Client.Response;
 import com.rabbitmq.stream.impl.Client.StreamParametersBuilder;
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.buffer.UnpooledByteBufAllocator;
 import java.io.ByteArrayOutputStream;
 import java.io.DataOutputStream;
 import java.net.UnknownHostException;
@@ -477,9 +479,11 @@ void consume() throws Exception {
     client.close();
   }
 
-  @Test
-  void publishAndConsume() throws Exception {
-    int publishCount = 1000000;
+  @ParameterizedTest
+  @ValueSource(booleans = {true, false})
+  void publishAndConsume(boolean directBuffer) throws Exception {
+    ByteBufAllocator allocator = new UnpooledByteBufAllocator(directBuffer);
+    int publishCount = 1_000_000;
 
     CountDownLatch consumedLatch = new CountDownLatch(publishCount);
     Client.ChunkListener chunkListener =
@@ -494,6 +498,7 @@ void publishAndConsume() throws Exception {
     Client client =
         cf.get(
             new Client.ClientParameters()
+                .byteBufAllocator(allocator)
                 .chunkListener(chunkListener)
                 .messageListener(messageListener));
     client.subscribe(b(1), stream, OffsetSpecification.first(), credit);
@@ -504,6 +509,7 @@ void publishAndConsume() throws Exception {
               Client publisher =
                   cf.get(
                       new Client.ClientParameters()
+                          .byteBufAllocator(allocator)
                           .publishConfirmListener(
                               (publisherId, correlationId) -> confirmedLatch.countDown()));
               int messageId = 0;