    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.Comparator;
    024
    025    import cascading.tuple.Fields;
    026    import cascading.tuple.Tuple;
    027
    028    /**
    029     *
    030     */
    031    public class SparseTupleComparator implements Comparator<Tuple>
    032      {
    033      private final static Comparator DEFAULT = new NaturalComparator();
    034
    035      private static class NaturalComparator implements Comparator<Object>
    036        {
    037        @Override
    038        public int compare( Object lhs, Object rhs )
    039          {
    040          if( lhs == null && rhs == null )
    041            return 0;
    042          else if( lhs == null )
    043            return -1;
    044          else if( rhs == null )
    045            return 1;
    046          else
    047            return ( (Comparable) lhs ).compareTo( rhs ); // guaranteed to not be null
    048          }
    049        }
    050
    051      final Comparator[] comparators;
    052      final int[] posMap;
    053
    054      public SparseTupleComparator( Fields valuesField, Fields sortFields )
    055        {
    056        this( valuesField, sortFields, null );
    057        }
    058
    059      public SparseTupleComparator( Fields groupFields, Comparator defaultComparator )
    060        {
    061        this( groupFields, groupFields, defaultComparator );
    062        }
    063
    064      public SparseTupleComparator( Fields valuesFields, Fields sortFields, Comparator defaultComparator )
    065        {
    066        if( defaultComparator == null )
    067          defaultComparator = DEFAULT;
    068
    069        int size = valuesFields != null && !valuesFields.isUnknown() ? valuesFields.size() : sortFields.size();
    070        comparators = new Comparator[ size ];
    071        posMap = new int[ size ];
    072
    073        Comparator[] sortFieldComparators = sortFields.getComparators(); // returns a copy
    074
    075        for( int i = 0; i < sortFields.size(); i++ )
    076          {
    077          Comparable field = sortFields.get( i );
    078          int pos = valuesFields != null ? valuesFields.getPos( field ) : i;
    079
    080          comparators[ i ] = sortFieldComparators[ i ];
    081          posMap[ i ] = pos;
    082
    083          if( comparators[ i ] == null )
    084            comparators[ i ] = defaultComparator;
    085          }
    086        }
    087
    088      public Comparator[] getComparators()
    089        {
    090        return comparators;
    091        }
    092
    093      @Override
    094      public int compare( Tuple lhs, Tuple rhs )
    095        {
    096        for( int i = 0; i < comparators.length; i++ )
    097          {
    098          Comparator comparator = comparators[ i ];
    099
    100          if( comparator == null )
    101            continue;
    102
    103          int pos = posMap[ i ];
    104          int c = comparator.compare( lhs.getObject( pos ), rhs.getObject( pos ) );
    105
    106          if( c != 0 )
    107            return c;
    108          }
    109
    110        return 0;
    111        }
    112      }