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 /**
47 * Creates a new CsnFactory instance
48 * @param replicaId The replica ID
49 */
50 public CsnFactory( int replicaId )
51 {
52 changeCount = 0;
53 this.replicaId = replicaId;
54 }
55
56
57 /**
58 * Returns a new {@link Csn}.
59 * Generated CSN can be duplicate if user generates CSNs more than 2G
60 * times a milliseconds.
61 *
62 * @return The new generated CSN
63 */
64 public Csn newInstance()
65 {
66 int tmpChangeCount = 0;
67
68 synchronized ( lock )
69 {
70 long newTimestamp = System.currentTimeMillis();
71
72 // We will be able to generate 2 147 483 647 CSNs each 10 ms max
73 if ( lastTimestamp == newTimestamp )
74 {
75 changeCount++;
76 }
77 else
78 {
79 lastTimestamp = newTimestamp;
80 changeCount = 0;
81 }
82
83 tmpChangeCount = changeCount;
84 }
85
86 return new Csn( lastTimestamp, tmpChangeCount, replicaId, 0 );
87 }
88
89
90 /**
91 * Returns a new {@link Csn} created from the given values.
92 *
93 * This method is <b>not</b> to be used except for test purposes.
94 *
95 * @param timestamp The timestamp to use
96 * @param changeCount The change count to use
97 * @return The new generated CSN
98 */
99 public Csn newInstance( long timestamp, int changeCount )
100 {
101 return new Csn( timestamp, changeCount, replicaId, 0 );
102 }
103
104
105 /**
106 * Generates a CSN used to purge data. Its replicaID is not associated
107 * to a server.
108 *
109 * @param expirationDate The time up to the first CSN we want to keep
110 * @return The new generated CSN
111 */
112 public Csn newPurgeCsn( long expirationDate )
113 {
114 return new Csn( expirationDate, Integer.MAX_VALUE, PURGE_INSTANCEID, Integer.MAX_VALUE );
115 }
116
117
118 /**
119 * Sets the replica ID
120 * @param replicaId The replica ID
121 */
122 public void setReplicaId( int replicaId )
123 {
124 this.replicaId = replicaId;
125 }
126 }