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.api.ldap.model.csn;
21
22
23 /**
24 * Generates a new {@link Csn}.
25 *
26 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
27 */
28 public class CsnFactory
29 {
30 /** The last timestamp */
31 private static volatile long lastTimestamp;
32
33 /** The integer used to disambiguate CSN generated at the same time */
34 private int changeCount;
35
36 /** The replicaId to use for every CSN created by this factory */
37 private int replicaId;
38
39 /** A special instance ID for a purge CSN */
40 private static final int PURGE_INSTANCEID = 0x0FFF;
41
42 /** A lock used during the instance creation */
43 private Object lock = new Object();
44
45
46 public CsnFactory( int replicaId )
47 {
48 changeCount = 0;
49 this.replicaId = replicaId;
50 }
51
52
53 /**
54 * Returns a new {@link Csn}.
55 * Generated CSN can be duplicate if user generates CSNs more than 2G
56 * times a milliseconds.
57 */
58 public Csn newInstance()
59 {
60 int changeCount = 0;
61
62 synchronized ( lock )
63 {
64 long newTimestamp = System.currentTimeMillis();
65
66 // We will be able to generate 2 147 483 647 CSNs each 10 ms max
67 if ( lastTimestamp == newTimestamp )
68 {
69 this.changeCount++;
70 }
71 else
72 {
73 lastTimestamp = newTimestamp;
74 this.changeCount = 0;
75 }
76
77 changeCount = this.changeCount;
78 }
79
80 return new Csn( lastTimestamp, changeCount, replicaId, 0 );
81 }
82
83
84 /**
85 * Returns a new {@link Csn} created from the given values.
86 *
87 * This method is <b>not</b> to be used except for test purposes.
88 *
89 * @param timestamp The timestamp to use
90 * @param changeCount The change count to use
91 */
92 public Csn newInstance( long timestamp, int changeCount )
93 {
94 return new Csn( timestamp, changeCount, replicaId, 0 );
95 }
96
97
98 /**
99 * Generates a CSN used to purge data. Its replicaID is not associated
100 * to a server.
101 *
102 * @param expirationDate The time up to the first CSN we want to keep
103 */
104 public Csn newPurgeCsn( long expirationDate )
105 {
106 return new Csn( expirationDate, Integer.MAX_VALUE, PURGE_INSTANCEID, Integer.MAX_VALUE );
107 }
108
109
110 public void setReplicaId( int replicaId )
111 {
112 this.replicaId = replicaId;
113 }
114 }