streampacket.java

来自「java语言开发的P2P流媒体系统」· Java 代码 · 共 110 行

/* 
 * 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;

import java.security.*;
import p2pradio.packets.security.*;

public abstract class StreamPacket extends Packet
{	
	private long seqNr;
	private long timeStamp;
	private int signStartOffset;
	
	public StreamPacket(byte packetType, byte content[], long seqNr, long timeStamp)
	{
		super(packetType, content);
		
		signStartOffset = offset;
		
		// Sequenznummer speichern
		writeLong(seqNr);
		this.seqNr = seqNr;
		
		// Zeitstempel speichern
		writeLong(timeStamp);
		this.timeStamp = timeStamp;
	}
	
	protected StreamPacket(byte content[], int contentLength)
	{
		super(content, contentLength);
		
		signStartOffset = offset;
		
		// Sequenznummer lesen
		seqNr = readLong();
		
		// Zeitstempel lesen
		timeStamp = readLong();
	}
	
	public void sign(SignatureGenerator signatureGenerator) throws SignatureException
	{			
		int signatureLength = signatureGenerator.sign(content, signStartOffset, offset - signStartOffset, content, offset + 4, contentLength - (offset + 4));
		
		// L鋘ge der Signatur speichern
		writeInt(signatureLength);
		
		offset += signatureLength;
	}
	
	public boolean verify(SignatureChecker signatureChecker) throws SignatureException
	{
		if (!(signatureChecker instanceof SignatureCheckerDummy))
		{
			// L鋘ge der Signatur lesen
			int length = readInt();
			
			checkBytesLeft(length);
			
			// Signatur 黚erpr黤en
			boolean result = signatureChecker.verify(content, signStartOffset, (offset - 4) - signStartOffset, content, offset, contentLength - offset);
			offset += length;
			
			return result;
		}
		else
		{
			// Die Signatur nicht 黚erpr黤en
			return true;
		}
	}
	
	protected static int getMaxLength()
	{
		// Signaturl鋘ge: War bisher immer unter 50 Bytes lang
		return SimplePacket.getMaxLength() + 8 + 8 + 4 + 70;
	}
	
	public long getSeqNr()
	{
		return seqNr;
	}
	
	public long getTimeStamp()
	{
		return timeStamp;
	}
}