    001/*
    002 * Copyright (c) 2016 Chris K Wensel <chris@wensel.net>. All Rights Reserved.
    003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    004 *
    005 * Project and contact information: http://www.cascading.org/
    006 *
    007 * This file is part of the Cascading project.
    008 *
    009 * Licensed under the Apache License, Version 2.0 (the "License");
    010 * you may not use this file except in compliance with the License.
    011 * You may obtain a copy of the License at
    012 *
    013 *     http://www.apache.org/licenses/LICENSE-2.0
    014 *
    015 * Unless required by applicable law or agreed to in writing, software
    016 * distributed under the License is distributed on an "AS IS" BASIS,
    017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    018 * See the License for the specific language governing permissions and
    019 * limitations under the License.
    020 */
    021
    022package cascading.flow.stream.duct;
    023
    024import java.util.Iterator;
    025
    026/**
    027 *
    028 */
    029public class OpenReducingDuct<Incoming, Outgoing> extends Duct<Grouping<Incoming, Iterator<Incoming>>, Outgoing> implements OpenWindow
    030  {
    031  final Reducing reducing;
    032
    033  public OpenReducingDuct( Duct<Outgoing, ?> next )
    034    {
    035    super( next );
    036
    037    reducing = (Reducing) getNext();
    038    }
    039
    040  @Override
    041  public void receive( Duct previous, int ordinal, Grouping<Incoming, Iterator<Incoming>> grouping )
    042    {
    043    // don't start a grouping if there are no values in the group
    044    if( !grouping.joinIterator.hasNext() )
    045      return;
    046
    047    reducing.startGroup( previous, grouping.key );
    048
    049    while( grouping.joinIterator.hasNext() )
    050      next.receive( this, 0, (Outgoing) grouping.joinIterator.next() );
    051
    052    reducing.completeGroup( previous, grouping.key );
    053    }
    054  }