playerinputstream.java

java语言开发的P2P流媒体系统

/* 
 * 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.players;

import p2pradio.Messages;
import p2pradio.event.*;
import p2pradio.logging.Logger;
import java.io.InputStream;
import java.io.IOException;


/**
 * Takes the data that a {@link ListenBuffer} provides and allows it
 * to be accessed as a usual {@link java.io.InputStream}.
 *
 * @author Michael Kaufmann
 */
public class PlayerInputStream extends InputStream implements DataLeapListener
{
	private ListenBuffer buffer;
	
	// Das "angebrauchte" Datenpaket
	private byte[] currentData;
	private int dataOffset;
	private int dataLength;
	
	// Wieviel wurde vom "angebrauchten" Datenpaket schon gelesen?
	private int alreadyRead = 0;
	
	// Ist es das erste Mal, dass Daten abgeholt werden?
	private boolean firstTime = true;
	
	private boolean continueIfDataLeap;
	private boolean dataLeap = false;
	
	
	/**
	 * Creates a Player Input Stream with <code>player</code> as source.
	 * If the consumer of this input stream is too slow <code>continueIfTooSlow</code> determines
	 * if the input stream should skip some stream data and continue, or if the stream should end. 
	 * 
	 */
	public PlayerInputStream(ListenBuffer buffer, boolean continueIfDataLeap)
	{
		super();
		this.buffer = buffer;
		this.continueIfDataLeap = continueIfDataLeap;
		
		buffer.addDataLeapListener(this);
	}
	
	public void dataLeap(DataLeapEvent e)
	{
		dataLeap = true;
	}
	
	public int available() throws IOException
	{
		// Die Anzahl restliche Bytes im Datenpaket zur點kgeben
		return dataLength - alreadyRead;
	}
	
	public int read() throws IOException
	{
		if (currentData == null)
		{
			try
			{
				getNextData();
			}
			catch (IOException e)
			{
				// Player ist zu langsam
				return -1;
			}
		}

		int value = (currentData[dataOffset + alreadyRead] & 0xff);
		alreadyRead++;
		
		if (alreadyRead == dataLength)
		{
			// N鋍hstes Mal m黶sen neue Daten besorgt werden
			currentData = null;
		}
		
		return value;
	}
	
	public int read(byte b[], int off, int len) throws IOException
	{
		if (b == null)
		{
			throw new NullPointerException();
		}
		else if ((off < 0) || (off > b.length) || (len < 0) ||
		 ((off + len) > b.length) || ((off + len) < 0))
		{
			throw new IndexOutOfBoundsException();
		}
		else if (len == 0)
		{
			return 0;
		}

		if (currentData == null)
		{
			try
			{
				getNextData();
			}
			catch (IOException e)
			{
				// Player ist zu langsam
				return -1;	
			}
		}

		// Restliche Bytes des Datenpakets zur點kgeben
		// (kein neues Paket anfordern, sonst k鰊nte die Methode blockieren)

		int bytesToRead = Math.min(available(), len);
		
		System.arraycopy(currentData, dataOffset + alreadyRead, b, off, bytesToRead);
		alreadyRead += bytesToRead;

		if (alreadyRead == dataLength)
		{
			// N鋍hstes Mal m黶sen neue Daten besorgt werden
			currentData = null;
		}

		return bytesToRead;
	}
	
	private void getNextData() throws IOException
	{
		// Die Daten abholen
		if (firstTime)
		{
			firstTime = false;
		}
		else
		{
			buffer.nextDataPacket();
		}
		
		if (dataLeap)
		{
			Logger.finer("PlayerInputStream", "PlayerInputStream.DATA_LEAP"); //$NON-NLS-1$ //$NON-NLS-2$
			
			if (!continueIfDataLeap)
			{
				throw new IOException(Messages.getString("PlayerInputStream.DATA_LEAP")); //$NON-NLS-1$
			}
		}	
	
		currentData = buffer.getData();
		dataOffset = buffer.getDataOffset();
		dataLength = buffer.getDataLength();
			
		alreadyRead = 0;
	}	
}