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();
    }
}