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