Allow to @OverRide the cumulative ChannelBuffer creation. See netty#169

codec/src/main/java/io/netty/handler/codec/frame/FrameDecoder.java

@@ -363,10 +363,20 @@ private void cleanup(ChannelHandlerContext ctx, ChannelStateEvent e)
     private ChannelBuffer cumulation(ChannelHandlerContext ctx) {
         ChannelBuffer c = cumulation;
         if (c == null) {
-            c = ChannelBuffers.dynamicBuffer(
-                    ctx.getChannel().getConfig().getBufferFactory());
+            c = createCumulationDynamicBuffer(ctx);
             cumulation = c;
         }
         return c;
     }
+
+    /**
+     * Create a new {@link ChannelBuffer} which is used for the cumulation. Be aware that this MUST be a dynamic buffer. Sub-classes may override this to provide a 
+     * dynamic {@link ChannelBuffer} which has some prelocated size that better fit their need.
+     * 
+     * @param ctx {@link ChannelHandlerContext} for this handler
+     * @return buffer the {@link ChannelBuffer} which is used for cumulation
+     */
+    protected ChannelBuffer createCumulationDynamicBuffer(ChannelHandlerContext ctx) {
+        return ChannelBuffers.dynamicBuffer(ctx.getChannel().getConfig().getBufferFactory());
+    }
 }