public class Bounded implements Link {
    private Object[] buffer;
    private int head, tail, len;
    private boolean closed;

    public Bounded( int size ) {
	buffer = new Object[size];
	head = tail = 0;
	len = 0;
	closed = false;
    }

    public synchronized void send( Object o ) {
	while ( len >= buffer.length ) {
	    try {
		wait();
	    }
	    catch( InterruptedException ex ) {
	    }
	}
	buffer[ head ] = o;
	head = ( head + 1 ) % buffer.length;
	len++;
	notify();
    }

    public synchronized Object recv() {
	if ( len == 0 && closed )
	    return null;
	while ( len == 0 ) {
	    try {
		wait();
	    }
	    catch( InterruptedException ex ) {
	    }
	    if ( len == 0 && closed ) return null;
	}
	Object o = buffer[tail];
	tail = (tail+1) % buffer.length;
	len--;
	notify();
	return o;
    }

    public synchronized void close() {
	closed = true;
	notify();
    }

    public synchronized int getSize() {
	return len;
    }
}