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 }