datapacket.java

来自「java语言开发的P2P流媒体系统」· Java 代码 · 共 167 行

/* Stream-2-Stream - Peer to peer television and radio
 * This file has been modified from the original P2P-Radio source
 * Project homepage: http://s2s.sourceforge.net/
 * Copyright (C) 2005-2006 Jason Hooks
 */

/* 
 * P2P-Radio - Peer to peer streaming system
 * Project homepage: http://p2p-radio.sourceforge.net/
 * Copyright (C) 2003-2004 Michael Kaufmann <[e-mail]>
 * 
 * ---------------------------------------------------------------------------
 * 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 2 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 p2pradio.packets;

public class DataPacket extends StreamPacket
{	
	private long headerSeqNr;
	private long metadataSeqNr;
	
	// Die Daten werden nicht noch extra in einem
	// eigenen Array gespeichert
	private int dataOffset;
	private int dataLength;
	
	public DataPacket(long seqNr, long timeStamp, long headerSeqNr, long metadataSeqNr, byte data[])
	{
		this(new byte[getMaxLength() + data.length], seqNr, timeStamp, headerSeqNr, metadataSeqNr, data, 0, data.length);
	}
	
	public DataPacket(byte content[], long seqNr, long timeStamp, long headerSeqNr, long metadataSeqNr, byte[] data)
	{
		this(content, seqNr, timeStamp, headerSeqNr, metadataSeqNr, data, 0, data.length);
	}
	
	public DataPacket(long seqNr, long timeStamp, long headerSeqNr, long metadataSeqNr, byte data[], int dataLength)
	{
		this(new byte[getMaxLength() + dataLength], seqNr, timeStamp, headerSeqNr, metadataSeqNr, data, 0, dataLength);
	}
	
	public DataPacket(byte content[], long seqNr, long timeStamp, long headerSeqNr, long metadataSeqNr, byte[] data, int dataLength)
	{
		this(content, seqNr, timeStamp, headerSeqNr, metadataSeqNr, data, 0, dataLength);
	}
	
	public DataPacket(long seqNr, long timeStamp, long headerSeqNr, long metadataSeqNr, byte data[], int dataOffset, int dataLength)
	{
		this(new byte[getMaxLength() + dataLength], seqNr, timeStamp, headerSeqNr, metadataSeqNr, data, dataOffset, dataLength);
	}

	protected DataPacket(byte content[], long seqNr, long timeStamp, long headerSeqNr, long metadataSeqNr, byte[] data, int dataOffset, int dataLength)
	{
		super(Packet.DATA, content, seqNr, timeStamp);
		
		// Header-Sequenznummer speichern
		writeLong(headerSeqNr);
		this.headerSeqNr = headerSeqNr;
		
		// Metadaten-Sequenznummer speichern
		writeLong(metadataSeqNr);
		this.metadataSeqNr = metadataSeqNr;
		
		// L鋘ge der Daten speichern
		writeInt(dataLength);
		
		this.dataOffset = offset;
		this.dataLength = dataLength;
		
		checkBytesLeft(dataLength);
		
		// Daten kopieren
		System.arraycopy(data, dataOffset, content, offset, dataLength);
		offset += dataLength;
	}
	
	protected DataPacket(byte content[], int contentLength)
	{
		super(content, contentLength);
		
		// Header-Sequenznummer lesen
		headerSeqNr = readLong();
		
		// Metadaten-Sequenznummer lesen
		metadataSeqNr = readLong();
		
		// L鋘ge der Daten lesen
		int length = readInt();
		
		checkBytesLeft(length);
		
		dataOffset = offset;
		dataLength = length;
		
		offset += length;
	}
	
	// Die Methode getMaxLength() gibt hier nur eine
	// Mindestl鋘ge zur點k
	// Sie ist "public", weil sie von Source.java gebraucht wird
	
	//jhooks NOTE - The following method does not get the actual max length of the packet!!!!!
	//It returns the maxLength for the first part, which is required info such as timestamp, seqnr, headerSeqNr, MetadataSeqNr
	//Most of this required info is used for keeping track of the packets in the Buffer.java
	
	//This info is put together with the second part data[] (actual information you want to send) into a byte array content[];
	//When the packet is sent, both parts (data and required info) are passed to the next peer
	
	//The actual max length of a packet is TCP_MAX_MESSAGE_SIZE (10,000) in PacketFactory.java 
	public static int getMaxLength()
	{
		return StreamPacket.getMaxLength() + 8 + 8 + 4 + 4;
	}
	
	protected String getTypeString()
	{
		return "Data"; //$NON-NLS-1$
	}
	
	public long getHeaderSeqNr()
	{
		return headerSeqNr;
	}
	
	public long getMetadataSeqNr()
	{
		return metadataSeqNr;
	}
	
	public byte[] getData()
	{
		return content;
	}
	
	public int getDataOffset()
	{
		return dataOffset;
	}
	
	public int getDataLength()
	{
		return dataLength;
	}
	
	public byte[] createDataArray()
	{
		byte[] data = new byte[dataLength];
		System.arraycopy(content, dataOffset, data, 0, dataLength);
		
		return data;
	}
}