abstractpacket.java

mysql集群

/*
 * 	This program is free software; you can redistribute it and/or modify it under the terms of 
 * the GNU 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 General Public License for more details. 
 * 	You should have received a copy of the GNU 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.mysql.net.packet;

import java.io.UnsupportedEncodingException;

import org.apache.log4j.Logger;

import com.meidusa.amoeba.mysql.io.MySqlPacketConstant;
import com.meidusa.amoeba.net.packet.AbstractPacketBuffer;

/**
 * 
 * @author <a href=mailto:[e-mail]>Struct chen</a>
 *
 */
public class AbstractPacket extends com.meidusa.amoeba.net.packet.AbstractPacket implements MySqlPacketConstant {
	protected static Logger logger = Logger.getLogger(AbstractPacket.class);
	/**
	 * 只表示数据长度，不包含包头长度
	 */
	public int packetLength;
	
	/**
	 * 当前的数据包序列数
	 */
	public byte packetId;
	
	@Override
	protected void init(AbstractPacketBuffer buffer) {
		buffer.setPosition(0);
		packetLength = (buffer.readByte() & 0xff)	
		+ ((buffer.readByte() & 0xff) << 8)	
		+ ((buffer.readByte() & 0xff) << 16);
		packetId = buffer.readByte();
	}
	
	/**
	 * 估算packet的大小，估算的太大浪费内存，估算的太小会影响性能
	 * @return
	 */
	protected int calculatePacketSize(){
		return HEADER_SIZE + 1;
	}

	@Override
	protected void write2Buffer(AbstractPacketBuffer buffer)
			throws UnsupportedEncodingException {
		// TODO Auto-generated method stub
		
	}

	@Override
	protected void afterPacketWritten(AbstractPacketBuffer buffer) {
		int position = buffer.getPosition();
		packetLength = position-HEADER_SIZE;
		buffer.setPosition(0);
		buffer.writeByte((byte)(packetLength & 0xff));
		buffer.writeByte((byte) (packetLength >>> 8));
		buffer.writeByte((byte) (packetLength >>> 16));
		buffer.writeByte((byte) (packetId & 0xff));// packet id
		buffer.setPosition(position);
	}

	@Override
	protected Class<? extends AbstractPacketBuffer> getPacketBufferClass() {
		return MysqlPacketBuffer.class;
	}

}