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();
    }
}