    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.concurrent.atomic.AtomicInteger;
    024
    025    import cascading.flow.FlowElement;
    026    import cascading.flow.FlowProcess;
    027    import cascading.tuple.TupleEntry;
    028
    029    /**
    030     *
    031     */
    032    public class MergeStage extends ElementStage<TupleEntry, TupleEntry> implements Collapsing
    033      {
    034      private boolean started = false;
    035      protected final AtomicInteger completeCount = new AtomicInteger( 0 );
    036      private int numIncomingPaths;
    037
    038      public MergeStage( FlowProcess flowProcess, FlowElement flowElement )
    039        {
    040        super( flowProcess, flowElement );
    041        }
    042
    043      @Override
    044      public void bind( StreamGraph streamGraph )
    045        {
    046        super.bind( streamGraph );
    047
    048        numIncomingPaths = streamGraph.countAllEventingPathsTo( this );
    049        }
    050
    051      @Override
    052      public void initialize()
    053        {
    054        super.initialize();
    055
    056        completeCount.set( numIncomingPaths );
    057        }
    058
    059      @Override
    060      public synchronized void start( Duct previous )
    061        {
    062        if( started )
    063          return;
    064
    065        super.start( previous );
    066        started = true;
    067        }
    068
    069      @Override
    070      public void complete( Duct previous )
    071        {
    072        if( completeCount.decrementAndGet() != 0 )
    073          return;
    074
    075        super.complete( previous );
    076        completeCount.set( numIncomingPaths );
    077        }
    078      }