    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.tuple.hadoop.util;
    022
    023    import java.io.InputStream;
    024    import java.util.Comparator;
    025
    026    import cascading.CascadingException;
    027    import cascading.tuple.StreamComparator;
    028    import cascading.tuple.hadoop.io.HadoopTupleInputStream;
    029    import cascading.tuple.hadoop.io.HadoopTupleOutputStream;
    030
    031    /**
    032     *
    033     */
    034    public class TupleElementStreamComparator implements StreamComparator<HadoopTupleInputStream>, Comparator<Object>
    035      {
    036      final StreamComparator comparator;
    037
    038      public TupleElementStreamComparator( StreamComparator comparator )
    039        {
    040        this.comparator = comparator;
    041        }
    042
    043      @Override
    044      public int compare( Object lhs, Object rhs )
    045        {
    046        return ( (Comparator<Object>) comparator ).compare( lhs, rhs );
    047        }
    048
    049      @Override
    050      public int compare( HadoopTupleInputStream lhsStream, HadoopTupleInputStream rhsStream )
    051        {
    052        try
    053          {
    054          // pop off element type, its assumed we know it as we have a stream comparator
    055          // to delegate too
    056          int lhsToken = lhsStream.readToken();
    057          int rhsToken = rhsStream.readToken();
    058
    059          if( lhsToken == HadoopTupleOutputStream.WRITABLE_TOKEN )
    060            lhsStream.readString();
    061
    062          if( rhsToken == HadoopTupleOutputStream.WRITABLE_TOKEN )
    063            rhsStream.readString();
    064
    065          InputStream lhs = lhsToken == 0 ? null : lhsStream.getInputStream();
    066          InputStream rhs = rhsToken == 0 ? null : rhsStream.getInputStream();
    067
    068          return comparator.compare( lhs, rhs );
    069          }
    070        catch( Exception exception )
    071          {
    072          throw new CascadingException( "unable to compare Tuples, likely a CoGroup is being attempted on fields of " +
    073            "different types or custom comparators are incorrectly set on Fields", exception );
    074          }
    075        }
    076      }