Add PooledSlicedByteBuf and PooledDuplicatedByteBuf

Motivation:

At the moment when calling slice(...) or duplicate(...) on a Pooled*ByteBuf a new SlicedByteBuf or DuplicatedByteBuf. This can create a lot of GC.

Modifications:

Add PooledSlicedByteBuf and PooledDuplicatedByteBuf which will be used when a PooledByteBuf is used.

Result:

Less GC.

buffer/src/main/java/io/netty/buffer/AbstractDerivedByteBuf.java

@@ -59,12 +59,20 @@ public abstract class AbstractDerivedByteBuf extends AbstractByteBuf {
 
     @Override
     public final boolean release() {
-        return unwrap().release();
+        if (unwrap().release()) {
+            deallocate();
+            return true;
+        }
+        return false;
     }
 
     @Override
     public final boolean release(int decrement) {
-        return unwrap().release(decrement);
+        if (unwrap().release(decrement)) {
+            deallocate();
+            return true;
+        }
+        return false;
     }
 
     @Override
@@ -76,4 +84,9 @@ public abstract class AbstractDerivedByteBuf extends AbstractByteBuf {
     public ByteBuffer nioBuffer(int index, int length) {
         return unwrap().nioBuffer(index, length);
     }
+
+    /**
+     * Called when the wrapped {@link ByteBuf} was released due calling of {@link #release()} or {@link #release(int)}.
+     */
+    protected void deallocate() { }
 }

buffer/src/main/java/io/netty/buffer/DuplicatedByteBuf.java

@@ -33,11 +33,19 @@ import java.nio.channels.ScatteringByteChannel;
  */
 public class DuplicatedByteBuf extends AbstractDerivedByteBuf {
 
-    private final ByteBuf buffer;
+    private ByteBuf buffer;
 
     public DuplicatedByteBuf(ByteBuf buffer) {
         super(buffer.maxCapacity());
+        init(buffer);
+    }
 
+    DuplicatedByteBuf(int maxCapacity) {
+        super(maxCapacity);
+    }
+
+    final void init(ByteBuf buffer) {
+        maxCapacity(buffer.maxCapacity());
         if (buffer instanceof DuplicatedByteBuf) {
             this.buffer = ((DuplicatedByteBuf) buffer).buffer;
         } else {
@@ -45,6 +53,8 @@ public class DuplicatedByteBuf extends AbstractDerivedByteBuf {
         }
 
         setIndex(buffer.readerIndex(), buffer.writerIndex());
+        markReaderIndex();
+        markWriterIndex();
     }
 
     @Override

buffer/src/main/java/io/netty/buffer/PooledByteBuf.java

@@ -70,6 +70,16 @@ abstract class PooledByteBuf<T> extends AbstractReferenceCountedByteBuf {
         initThread = Thread.currentThread();
     }
 
+    @Override
+    public ByteBuf slice(int index, int length) {
+        return PooledSlicedByteBuf.newInstance(this, index, length);
+    }
+
+    @Override
+    public ByteBuf duplicate() {
+        return PooledDuplicatedByteBuf.newInstance(this);
+    }
+
     @Override
     public final int capacity() {
         return length;

buffer/src/main/java/io/netty/buffer/PooledDuplicatedByteBuf.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2015 The Netty Project
+ *
+ * The Netty Project 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 io.netty.buffer;
+
+import io.netty.util.Recycler;
+
+final class PooledDuplicatedByteBuf extends DuplicatedByteBuf {
+
+    private static final Recycler<PooledDuplicatedByteBuf> RECYCLER = new Recycler<PooledDuplicatedByteBuf>() {
+        @Override
+        protected PooledDuplicatedByteBuf newObject(Handle handle) {
+            return new PooledDuplicatedByteBuf(handle);
+        }
+    };
+
+    static PooledDuplicatedByteBuf newInstance(ByteBuf buffer) {
+        PooledDuplicatedByteBuf buf = RECYCLER.get();
+        buf.init(buffer);
+        return buf;
+    }
+
+    private final Recycler.Handle recyclerHandle;
+
+    private PooledDuplicatedByteBuf(Recycler.Handle recyclerHandle) {
+        super(0);
+        this.recyclerHandle = recyclerHandle;
+    }
+
+    @Override
+    public ByteBuf slice(int index, int length) {
+        return PooledSlicedByteBuf.newInstance(this, index, length);
+    }
+
+    @Override
+    public ByteBuf duplicate() {
+        return newInstance(this);
+    }
+
+    @Override
+    protected void deallocate() {
+        RECYCLER.recycle(this, recyclerHandle);
+    }
+}

buffer/src/main/java/io/netty/buffer/PooledSlicedByteBuf.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2015 The Netty Project
+ *
+ * The Netty Project 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 io.netty.buffer;
+
+import io.netty.util.Recycler;
+
+final class PooledSlicedByteBuf extends SlicedByteBuf {
+
+    private static final Recycler<PooledSlicedByteBuf> RECYCLER = new Recycler<PooledSlicedByteBuf>() {
+        @Override
+        protected PooledSlicedByteBuf newObject(Handle handle) {
+            return new PooledSlicedByteBuf(handle);
+        }
+    };
+
+    static PooledSlicedByteBuf newInstance(ByteBuf buffer, int index, int length) {
+        PooledSlicedByteBuf buf = RECYCLER.get();
+        buf.init(buffer, index, length);
+        return buf;
+    }
+
+    private final Recycler.Handle recyclerHandle;
+
+    private PooledSlicedByteBuf(Recycler.Handle recyclerHandle) {
+        super(0);
+        this.recyclerHandle = recyclerHandle;
+    }
+
+    @Override
+    public ByteBuf slice(int index, int length) {
+        return newInstance(this, index, length);
+    }
+
+    @Override
+    public ByteBuf duplicate() {
+        return PooledDuplicatedByteBuf.newInstance(this);
+    }
+
+    @Override
+    protected void deallocate() {
+        RECYCLER.recycle(this, recyclerHandle);
+    }
+}

buffer/src/main/java/io/netty/buffer/SlicedByteBuf.java

@@ -34,12 +34,20 @@ import java.nio.channels.ScatteringByteChannel;
  */
 public class SlicedByteBuf extends AbstractDerivedByteBuf {
 
-    private final ByteBuf buffer;
+    private ByteBuf buffer;
-    private final int adjustment;
+    private int adjustment;
-    private final int length;
+    private int length;
 
     public SlicedByteBuf(ByteBuf buffer, int index, int length) {
         super(length);
+        init(buffer, index, length);
+    }
+
+    SlicedByteBuf(int length) {
+        super(length);
+    }
+
+    final void init(ByteBuf buffer, int index, int length) {
         if (index < 0 || index > buffer.capacity() - length) {
             throw new IndexOutOfBoundsException(buffer + ".slice(" + index + ", " + length + ')');
         }
@@ -55,8 +63,9 @@ public class SlicedByteBuf extends AbstractDerivedByteBuf {
             adjustment = index;
         }
         this.length = length;
-
+        maxCapacity(length);
-        writerIndex(length);
+        setIndex(0, length);
+        discardMarks();
     }
 
     @Override