/*
* 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.mysql.io;
import java.nio.ByteBuffer;
import com.meidusa.amoeba.net.io.PacketOutputStream;
/**
*
* <b> The Packet Header </b>
*
* <pre>
* Bytes Name
* ----- ----
* 3 Packet Length
* 1 Packet Number
* </p>
* <b>Packet Length:</b> The length, in bytes, of the packet
* that follows the Packet Header. There
* may be some special values in the most
* significant byte. Since 2**24 = MB,
* the maximum packet length is 16MB.
* </P>
* <b>Packet Number:</b> A serial number which can be used to
* ensure that all packets are present
* and in order. The first packet of a
* client query will have Packet Number = 0
* Thus, when a new SQL statement starts,
* the packet number is re-initialised.
*
* </pre>
*
* @see <href a="http://forge.mysql.com/wiki/MySQL_Internals_ClientServer_Protocol#The_Packet_Header">The_Packet_Header</a>
*
* @author <a href=mailto:piratebase@sina.com>Struct chen</a>
*
*/
public class MysqlFramingOutputStream extends PacketOutputStream implements MySqlPacketConstant{
protected byte packetId;
protected boolean packetwrittenWithHead;
/**
*
* @param packetwrittenWithHead 写数据的时候是否写入包头信息,true--表示写入数据的时候已经包括了包头信息,
* 否则则需要在调用{@link #returnPacketBuffer()} 的时候需要实时生成包头信息
*/
public MysqlFramingOutputStream(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){
/**
* 包头信息:长度--是不包含包头长度
*/
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) packetId);// packet id
}
_buffer.rewind();
return _buffer;
}
public void setPacketId(byte packetId){
this.packetId = packetId;
}
/**
*
*/
protected void initHeader(){
if(!packetwrittenWithHead){
_buffer.put(HEADER_PAD);
}
}
}