View Javadoc

1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  package org.apache.directory.server.core.partition.impl.btree;
21  
22  
23  import org.apache.directory.server.schema.SerializableComparator;
24  
25  
26  /**
27   * TupleComparator for index records.
28   *
29   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
30   * @version $Rev: 539571 $
31   */
32  public class ReverseIndexComparator<V> implements TupleComparator<Long,V>
33  {
34      private static final long serialVersionUID = 3257283621751633459L;
35  
36      /** The value comparison to use - keys are Longs */
37      private final SerializableComparator<V> valueComparator;
38  
39  
40      /**
41       * Creates an IndexComparator.
42       *
43       * @param valueComparator the table comparator to use for values
44       */
45      public ReverseIndexComparator( SerializableComparator<V> valueComparator )
46      {
47          this.valueComparator = valueComparator;
48      }
49  
50  
51      /**
52       * Gets the comparator used to compare keys.
53       *
54       * @return the comparator for comparing keys.
55       */
56      public SerializableComparator<Long> getKeyComparator()
57      {
58          return LongComparator.INSTANCE;
59      }
60  
61  
62      /**
63       * Gets the binary comparator used to compare values which are the values
64       * of attributes.
65       *
66       * @return the binary comparator for comparing values.
67       */
68      public SerializableComparator<V> getValueComparator()
69      {
70          return valueComparator;
71      }
72  
73  
74      /**
75       * Compares key Object to determine their sorting order returning a
76       * value = to, < or > than 0.
77       *
78       * @param l1 the first long key to compare
79       * @param l2 the other long key to compare to the first
80       * @return 0 if both are equal, a negative value less than 0 if the first
81       * is less than the second, or a postive value if the first is greater than
82       * the second byte array.
83       */
84      public int compareKey( Long l1, Long l2 )
85      {
86          return ( l1 < l2 ? -1 : ( l1.equals( l2 ) ? 0 : 1 ) );
87      }
88  
89  
90      /**
91       * Comparse value Objects to determine their sorting order returning a
92       * value = to, < or > than 0.
93       *
94       * @param v1 the first value to compare
95       * @param v2 the other value to compare to the first
96       * @return 0 if both are equal, a negative value less than 0 if the first
97       * is less than the second, or a postive value if the first is greater than
98       * the second Object.
99       */
100     public int compareValue( V v1, V v2 )
101     {
102         return valueComparator.compare( v1, v2 );
103     }
104 }