PageStream.java

package dolda.xiphutil;

import java.io.IOException;
import java.io.InputStream;
import com.jcraft.jogg.Page;
import com.jcraft.jogg.SyncState;

/**
 * The <code>PageStream</code> class decodes Ogg pages from a byte stream.
 * 
 * @author Fredrik Tolf <code><fredrik@dolda2000.com></code>
 */
public class PageStream {
	private SyncState sync = new SyncState();
	private final InputStream in;
	private boolean eos = false;

	/**
	 * Constructs a new <code>PageStream</code> object.
	 * 
	 * @param in
	 *            the Java IO <code>InputStream</code> to fetch pages from.
	 */
	public PageStream(InputStream in) {
		this.in = in;
		sync.init();
	}

	/**
	 * Fetches one page from the byte stream.
	 * 
	 * @return the page fetched, or <code>null</code> if at the end of the
	 *         stream.
	 * @exception java.io.IOException
	 *                if the <code>InputStream</code> itself throws an
	 *                <code>IOException</code>.
	 * @exception FormatException
	 *                if a format error is found in the stream.
	 */
	public Page page() throws IOException {
		if (eos)
			return (null);
		Page page = new Page();
		while (true) {
			int ret = sync.pageout(page);
			if (ret < 0)
				throw (new OggException()); /* ? */
			if (ret == 1) {
				if (page.eos() != 0)
					eos = true;
				return (page);
			}
			int off = sync.buffer(4096);
			int len = in.read(sync.data, off, 4096);
			if (len < 0)
				return (null);
			sync.wrote(len);
		}
	}

	/**
	 * 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();
	}
}