    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.util;
    022
    023import java.util.Comparator;
    024
    025import cascading.tuple.Fields;
    026import cascading.tuple.Tuple;
    027
    028/**
    029 *
    030 */
    031public 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  }