GatewayOutputStream.java example

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amoeba-master
/*
 * 	This program is free software; you can redistribute it and/or modify it under the terms of 
 * the GNU AFFERO GENERAL PUBLIC LICENSE as published by the Free Software Foundation; either version 3 of the License, 
 * or (at your option) any later version. 
 * 
 * 	This program 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 AFFERO GENERAL PUBLIC LICENSE for more details. 
 * 	You should have received a copy of the GNU AFFERO GENERAL PUBLIC LICENSE along with this program; 
 * if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
package com.meidusa.amoeba.gateway.io;

import java.nio.ByteBuffer;

import com.meidusa.amoeba.gateway.packet.GatewayPacketConstant;
import com.meidusa.amoeba.net.io.PacketOutputStream;

/**
 * <pre>
 * struct MsgHeader {
 *     int32   messageLength; // total message size, including this
 *     int32   requestID;     // identifier for this message
 *     int32   responseTo;    // requestID from the original request
 *                            //   (used in reponses from db)
 *     int32   opCode;        // request type - see table below
 * }
 * </pre>
 * @see <a href="http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-TableOfContents">mongodb wire protocol</a>
 * 
 * @author <a href=mailto:piratebase@sina.com>Struct chen</a>
 * 
 */
public class GatewayOutputStream extends PacketOutputStream implements GatewayPacketConstant{
	protected boolean packetwrittenWithHead;
	
	/**
	 * 
	 * @param packetwrittenWithHead д���ݵ�ʱ���Ƿ�д���ͷ��Ϣ��true--��ʾд�����ݵ�ʱ���Ѿ������˰�ͷ��Ϣ��
	 * 							   ��������Ҫ�ڵ���{@link #returnPacketBuffer()} ��ʱ����Ҫʵʱ���ɰ�ͷ��Ϣ
	 */
	public GatewayOutputStream(boolean packetwrittenWithHead){
		this.packetwrittenWithHead = packetwrittenWithHead;
		resetPacket();
	}
	public ByteBuffer returnPacketBuffer ()
    {
        // flip the buffer which will limit it to it's current position
        _buffer.flip();
        if(!packetwrittenWithHead){
	        /**
	         *  ��ͷ��Ϣ�����ȣ����ǲ�������ͷ����
	         */
	        int count = _buffer.limit()-HEADER_PAD.length;
	        _buffer.put((byte)(count & 0xff));
	        _buffer.put((byte) (count >> 8));
	        _buffer.put((byte) (count >> 16));
	        _buffer.put((byte) (count >> 24));
        }
        _buffer.rewind();
        return _buffer;
    }
	
	/**
	 * 
	 */
	protected void initHeader(){
		if(!packetwrittenWithHead){
			_buffer.put(HEADER_PAD);
		}
    }
}