Correct semantic of LocalChannel.doWrite(...) and remove memory copy

Motivation:

The semantic of LocalChannel.doWrite(...) were a bit off as it notified the ChannelFuture before the data was actual moved to the peer buffer.

Modifications:

- Use our MPSC queue as inbound buffer
- Directly copy to data to the inbound buffer of the peer and either success or fail the promise after each copy.

Result:

Correct semantic and less memory copies.

transport/src/main/java/io/netty/channel/local/LocalChannel.java

@@ -29,14 +29,14 @@ import io.netty.channel.SingleThreadEventLoop;
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.concurrent.SingleThreadEventExecutor;
 import io.netty.util.internal.InternalThreadLocalMap;
+import io.netty.util.internal.OneTimeTask;
+import io.netty.util.internal.PlatformDependent;
 
 import java.net.SocketAddress;
 import java.nio.channels.AlreadyConnectedException;
 import java.nio.channels.ClosedChannelException;
 import java.nio.channels.ConnectionPendingException;
 import java.nio.channels.NotYetConnectedException;
-import java.util.ArrayDeque;
-import java.util.Collections;
 import java.util.Queue;
 
 /**
@@ -49,7 +49,8 @@ public class LocalChannel extends AbstractChannel {
     private static final int MAX_READER_STACK_DEPTH = 8;
 
     private final ChannelConfig config = new DefaultChannelConfig(this);
-    private final Queue<Object> inboundBuffer = new ArrayDeque<Object>();
+    // To futher optimize this we could write our own SPSC queue.
+    private final Queue<Object> inboundBuffer = PlatformDependent.newMpscQueue();
     private final Runnable readTask = new Runnable() {
         @Override
         public void run() {
@@ -64,7 +65,6 @@ public class LocalChannel extends AbstractChannel {
             pipeline.fireChannelReadComplete();
         }
     };
-
     private final Runnable shutdownHook = new Runnable() {
         @Override
         public void run() {
@@ -286,29 +286,25 @@ public class LocalChannel extends AbstractChannel {
         final ChannelPipeline peerPipeline = peer.pipeline();
         final EventLoop peerLoop = peer.eventLoop();
 
-        if (peerLoop == eventLoop()) {
+        for (;;) {
-            for (;;) {
+            Object msg = in.current();
-                Object msg = in.current();
+            if (msg == null) {
-                if (msg == null) {
+                break;
-                    break;
-                }
-                peer.inboundBuffer.add(msg);
-                ReferenceCountUtil.retain(msg);
-                in.remove();
             }
+            try {
+                peer.inboundBuffer.add(ReferenceCountUtil.retain(msg));
+                in.remove();
+            } catch (Throwable cause) {
+                in.remove(cause);
+            }
+        }
+
+        if (peerLoop == eventLoop()) {
             finishPeerRead(peer, peerPipeline);
         } else {
-            // Use a copy because the original msgs will be recycled by AbstractChannel.
+            peerLoop.execute(new OneTimeTask() {
-            final Object[] msgsCopy = new Object[in.size()];
-            for (int i = 0; i < msgsCopy.length; i ++) {
-                msgsCopy[i] = ReferenceCountUtil.retain(in.current());
-                in.remove();
-            }
-
-            peerLoop.execute(new Runnable() {
                 @Override
                 public void run() {
-                    Collections.addAll(peer.inboundBuffer, msgsCopy);
                     finishPeerRead(peer, peerPipeline);
                 }
             });