Added LengthPrefixedFrameDecoder

src/main/java/org/jboss/netty/handler/codec/frame/LengthFieldBasedFrameDecoder.java

@@ -40,7 +40,7 @@ public class LengthFieldBasedFrameDecoder extends FrameDecoder {
 
     private final int maxFrameLength;
     private final int lengthFieldOffset;
-    private final int lengthFieldLength;
+    final int lengthFieldLength;
     private final int lengthFieldEndOffset;
     private final int lengthAdjustment;
     private volatile boolean discardingTooLongFrame;

src/main/java/org/jboss/netty/handler/codec/frame/LengthPrefixedFrameDecoder.java

@@ -0,0 +1,70 @@
+/*
+ * JBoss, Home of Professional Open Source
+ *
+ * Copyright 2009, Red Hat Middleware LLC, and individual contributors
+ * by the @author tags. See the COPYRIGHT.txt in the distribution for a
+ * full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+package org.jboss.netty.handler.codec.frame;
+
+import org.jboss.netty.buffer.ChannelBuffer;
+import org.jboss.netty.channel.Channel;
+import org.jboss.netty.channel.ChannelHandlerContext;
+
+/**
+ * A specialized version of {@link LengthFieldBasedFrameDecoder} which assumes
+ * the length field is always located at offset {@code 0} and removes the length
+ * field from the decoded frame.
+ *
+ * @author The Netty Project (netty-dev@lists.jboss.org)
+ * @author Trustin Lee (tlee@redhat.com)
+ * @version $Rev$, $Date$
+ */
+public class LengthPrefixedFrameDecoder extends LengthFieldBasedFrameDecoder {
+
+    private final boolean stripLengthField;
+
+    public LengthPrefixedFrameDecoder(int maxFrameLength, int lengthFieldLength) {
+        this(maxFrameLength, lengthFieldLength, 0, true);
+    }
+
+    public LengthPrefixedFrameDecoder(int maxFrameLength, int lengthFieldLength, boolean stripLengthField) {
+        this(maxFrameLength, lengthFieldLength, 0, stripLengthField);
+    }
+
+    public LengthPrefixedFrameDecoder(int maxFrameLength, int lengthFieldLength, int lengthAdjustment) {
+        this(maxFrameLength, lengthFieldLength, lengthAdjustment, true);
+    }
+
+    public LengthPrefixedFrameDecoder(int maxFrameLength, int lengthFieldLength, int lengthAdjustment, boolean stripLengthField) {
+        super(maxFrameLength, 0, lengthFieldLength, lengthAdjustment);
+        this.stripLengthField = stripLengthField;
+    }
+
+    @Override
+    protected Object decode(ChannelHandlerContext ctx, Channel channel,
+            ChannelBuffer buffer) throws Exception {
+        ChannelBuffer frame = (ChannelBuffer) super.decode(ctx, channel, buffer);
+        if (stripLengthField && frame != null) {
+            frame.skipBytes(lengthFieldLength);
+            return frame.slice();
+        }
+
+        return frame;
+    }
+}