PacketStream.java

package dolda.xiphutil;

import java.io.IOException;
import com.jcraft.jogg.Packet;
import com.jcraft.jogg.Page;
import com.jcraft.jogg.StreamState;

/**
 * The <code>Packet</code> class decodes Ogg packets from a page stream.
 * 
 * @author Fredrik Tolf <code><fredrik@dolda2000.com></code>
 */
public class PacketStream {
	private StreamState strm = null;
	private Page page = null;
	private final PageStream in;
	private boolean eos = false;

	/**
	 * Constructs a new <code>PacketStream</code> object.
	 * 
	 * @param in
	 *            the {@link PageStream} object to decode packets from.
	 */
	public PacketStream(PageStream in) {
		this.in = in;
	}

	/**
	 * Fetches one packet from the stream.
	 * 
	 * @return the packet fetched, or <code>null</code> if at the end of the
	 *         stream.
	 * @exception java.io.IOException
	 *                if the <code>PageStream</code> itself throws an
	 *                <code>IOException</code>.
	 * @exception FormatException
	 *                if a format error is found in the stream.
	 */
	public Packet packet() throws IOException {
		if (eos)
			return (null);
		if (strm == null) {
			strm = new StreamState();
			page = in.page();
			strm.init(page.serialno());
		}
		Packet pkt = new Packet();
		while (true) {
			int ret = strm.packetout(pkt);
			if (ret < 0)
				throw (new OggException()); /* ? */
			if (ret == 1)
				return (pkt);
			if (page == null) {
				if ((page = in.page()) == null) {
					eos = true;
					return (null);
				}
			}
			if (strm.pagein(page) != 0)
				throw (new OggException());
			page = null;
		}
	}

	/**
	 * Closes the stream backing this object.
	 * 
	 * @exception java.io.IOException
	 *                if the backing input stream itself throws an
	 *                <code>IOException</code>.
	 */
	public void close() throws IOException {
		in.close();
	}
}