/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.protocol.bgp.rib.impl;

import io.netty.handler.codec.LengthFieldBasedFrameDecoder;

/**
 * @see <a href="http://tools.ietf.org/html/rfc4271#section-4.1">BGP Message Header</a>
 */
public final class BGPMessageHeaderDecoder extends LengthFieldBasedFrameDecoder {

	private static final int MAX_FRAME_SIZE = 4096;

	private static final int MARKER_SIZE = 16;

	/*
	 * the length field represents the length of the whole message including the header
	 */
	private static final int LENGTH_SIZE = 2;

	/*
	 	
	 0                   1                   2                   3
	  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	  |                                                               |
	  |                                                               |
	  |                                                               |
	  |                                                               |
	  |                           Marker                              |
	  |                                                               |
	  |                                                               |
	  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	  |          Length               |      Type     |
	  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	  
	 */

	public BGPMessageHeaderDecoder() {
		super(MAX_FRAME_SIZE, MARKER_SIZE, LENGTH_SIZE, -MARKER_SIZE - LENGTH_SIZE, 0);
	}
}