/*
* 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 com.meidusa.amoeba.net.io.PacketInputStream;
/**
*
* <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 MysqlFramedInputStream extends PacketInputStream implements MySqlPacketConstant{
private byte _packetId;
private boolean readPackedWithHead;
public byte getPacketId(){
return _packetId;
}
public MysqlFramedInputStream(boolean readPackedWithHead){
this.readPackedWithHead = readPackedWithHead;
}
protected int decodeLength() {
/**
* 判断一下我们当前已经读取的数据包的数据是否比包头长,如果是:则可以计算整个包的长度,否则返回-1
*/
if (_have < getHeaderSize()) {
return -1;
}
_buffer.rewind();
/**
* mysql 数据部分＋包头=整个数据包长度
*/
int length = (_buffer.get() & 0xff)
+ ((_buffer.get() & 0xff) << 8)
+ ((_buffer.get() & 0xff) << 16)
+ this.getHeaderSize();
_packetId = _buffer.get();
_buffer.position(_have);
return length;
}
public int getHeaderSize() {
return HEADER_SIZE;
}
protected byte[] readPacket(){
byte[] msg = new byte[_length];
int position = _buffer.position();
if(readPackedWithHead){
_buffer.position(0);
}else{
_buffer.position(this.getHeaderSize());
}
_buffer.get(msg, 0, _length);
try{
_buffer.limit(_have);
_buffer.compact();
_buffer.position(position - _length);
_have -= _length;
_length = this.decodeLength();
}catch(IllegalArgumentException e){
throw new IllegalArgumentException("old position="+_buffer.position()+", new position="+_length+",old limit="+_buffer.limit() +", have(new limit)="+_have,e);
}
return msg;
}
}