#2183 Fix for releasing of the internal cumulation buffer in ByteToMessageDecoder

codec/src/main/java/io/netty/handler/codec/ByteToMessageDecoder.java

@@ -108,6 +108,8 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
             ByteBuf bytes = buf.readBytes(readable);
             buf.release();
             ctx.fireChannelRead(bytes);
+        } else {
+            buf.release();
         }
         cumulation = null;
         ctx.fireChannelReadComplete();

codec/src/test/java/io/netty/handler/codec/ByteToMessageDecoderTest.java

@@ -19,6 +19,7 @@ import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.embedded.EmbeddedChannel;
+import io.netty.util.ReferenceCountUtil;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -72,4 +73,50 @@ public class ByteToMessageDecoderTest {
         buf.release();
         b.release();
     }
+
+    /**
+     * Verifies that internal buffer of the ByteToMessageDecoder is released once decoder is removed from pipeline. In
+     * this case input is read fully.
+     */
+    @Test
+    public void testInternalBufferClearReadAll() {
+        final ByteBuf buf = ReferenceCountUtil.releaseLater(Unpooled.buffer().writeBytes(new byte[]{'a'}));
+        EmbeddedChannel channel = new EmbeddedChannel(new ByteToMessageDecoder() {
+            @Override
+            protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
+                ByteBuf byteBuf = internalBuffer();
+                Assert.assertEquals(1, byteBuf.refCnt());
+                in.readByte();
+                // Removal from pipeline should clear internal buffer
+                ctx.pipeline().remove(this);
+                Assert.assertEquals(0, byteBuf.refCnt());
+            }
+        });
+        Assert.assertFalse(channel.writeInbound(buf));
+        Assert.assertFalse(channel.finish());
+    }
+
+    /**
+     * Verifies that internal buffer of the ByteToMessageDecoder is released once decoder is removed from pipeline. In
+     * this case input was not fully read.
+     */
+    @Test
+    public void testInternalBufferClearReadPartly() {
+        final ByteBuf buf = ReferenceCountUtil.releaseLater(Unpooled.buffer().writeBytes(new byte[]{'a', 'b'}));
+        EmbeddedChannel channel = new EmbeddedChannel(new ByteToMessageDecoder() {
+            @Override
+            protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
+                ByteBuf byteBuf = internalBuffer();
+                Assert.assertEquals(1, byteBuf.refCnt());
+                in.readByte();
+                // Removal from pipeline should clear internal buffer
+                ctx.pipeline().remove(this);
+                Assert.assertEquals(0, byteBuf.refCnt());
+            }
+        });
+        Assert.assertTrue(channel.writeInbound(buf));
+        Assert.assertTrue(channel.finish());
+        Assert.assertEquals(channel.readInbound(), Unpooled.wrappedBuffer(new byte[] {'b'}));
+        Assert.assertNull(channel.readInbound());
+    }
 }