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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.xdbm;
21  
22  
23  import org.apache.directory.server.core.cursor.Cursor;
24  
25  
26  /**
27   * A Cursor introducing new advance methods designed to reduce some
28   * inefficiencies encountered when scanning over Tuples.
29   *
30   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
31   * @version $$Rev$$
32   */
33  public interface TupleCursor<K,V> extends Cursor<Tuple<K,V>>
34  {
35      /**
36       * An alternative to calling before(Tuple) which often may require
37       * wrapping a key in a newly created Tuple object that may be unnecessary.
38       * This method behaves just like before(Tuple) except it advances to just
39       * before the first value of the key.
40       *
41       * @param key the key to advance just before
42       * @throws Exception if there are faults peforming this operation
43       */
44      void beforeKey( K key ) throws Exception;
45  
46  
47      /**
48       * An alternative to calling after(Tuple) which often may require
49       * wrapping a key in a newly created Tuple object that may be unnecessary.
50       * This method behaves just like after(Tuple) except it advances to just
51       * after the last value of the key.
52       *
53       * @param key the key to advance just after the last value
54       * @throws Exception if there are faults peforming this operation
55       */
56      void afterKey( K key ) throws Exception;
57  
58  
59      /**
60       * An alternative to calling before(Tuple) which often may require
61       * wrapping a key and a value in a newly created Tuple object that may be
62       * unnecessary.  This method behaves just like before(Tuple) except it
63       * advances to just before the value of the key which may still be of the
64       * same key.  This method will not be supported if duplicate keys are not
65       * supported.  In this case an UnsupportedOperationException will be
66       * thrown.
67       *
68       * @param key the key of the value to advance just before
69       * @param value the value to advance just before
70       * @throws UnsupportedOperationException if duplicate keys not supporrted
71       * @throws Exception if there are faults peforming this operation
72       */
73      void beforeValue( K key, V value ) throws Exception;
74  
75  
76      /**
77       * An alternative to calling after(Tuple) which often may require
78       * wrapping a key and a value in a newly created Tuple object that may be
79       * unnecessary.  This method behaves just like after(Tuple) except it
80       * advances to just after the value with the specified key.  This method
81       * will not be supported if duplicate keys are not supported.  In this
82       * case an UnsupportedOperationException will be thrown.
83       *
84       * @param key the key of the value to advance just after
85       * @param value the value to advance just after
86       * @throws UnsupportedOperationException if duplicate keys not supporrted
87       * @throws Exception if there are faults peforming this operation
88       */
89      void afterValue( K key, V value ) throws Exception;
90  }