    001    /*
    002     * Copyright (c) 2007-2014 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
    021    package cascading.flow.stream;
    022
    023    import java.util.Iterator;
    024
    025    /**
    026     *
    027     */
    028    public 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      }