/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Sep 28, 2010
*/
package com.bigdata.bop.ap.filter;
import java.util.Iterator;
import java.util.Map;
import com.bigdata.bop.BOp;
import com.bigdata.bop.BOpBase;
import cutthecrap.utils.striterators.IFilter;
/**
* Base class for operators which apply striterator patterns for access paths.
* <p>
* The striterator pattern is enacted slightly differently here. The filter
* chain is formed by stacking {@link BOpFilterBase}s as child operands. Each
* operand specified to a {@link BOpFilterBase} must be a {@link BOpFilterBase} and
* layers on another filter, so you can stack filters as nested operands or as a
* sequence of operands.
* <p>
*
* @todo state as newState() and/or as annotation?
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
abstract public class BOpFilterBase extends BOpBase implements IFilter {
/**
*
*/
private static final long serialVersionUID = 1L;
public interface Annotations extends BOp.Annotations {
}
/**
* Deep copy.
* @param op
*/
public BOpFilterBase(BOpFilterBase op) {
super(op);
}
/**
* Shallow copy.
* @param args
* @param annotations
*/
public BOpFilterBase(BOp[] args, Map<String, Object> annotations) {
super(args, annotations);
}
final public Iterator filter(Iterator src, final Object context) {
// wrap source with each additional filter from the filter chain.
final Iterator<BOp> itr = argIterator();
while(itr.hasNext()) {
final BOp arg = itr.next();
src = ((BOpFilterBase) arg).filter(src, context);
}
// wrap src with _this_ filter.
src = filterOnce(src, context);
return src;
}
/**
* Wrap the source iterator with <i>this</i> filter.
*
* @param src
* The source iterator.
* @param context
* The iterator evaluation context.
*
* @return The wrapped iterator.
*/
abstract protected Iterator filterOnce(Iterator src, final Object context);
}