001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    https://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020package org.apache.directory.api.ldap.model.csn;
021
022
023/**
024 * Generates a new {@link Csn}.
025 * 
026 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
027 */
028public class CsnFactory
029{
030    /** The last timestamp */
031    private static volatile long lastTimestamp;
032
033    /** The integer used to disambiguate CSN generated at the same time */
034    private int changeCount;
035
036    /** The replicaId to use for every CSN created by this factory */
037    private int replicaId;
038
039    /** A special instance ID for a purge CSN */
040    private static final int PURGE_INSTANCEID = 0x0FFF;
041
042    /** A lock used during the instance creation */
043    private Object lock = new Object();
044
045
046    /**
047     * Creates a new CsnFactory instance
048     * @param replicaId The replica ID
049     */
050    public CsnFactory( int replicaId )
051    {
052        changeCount = 0;
053        this.replicaId = replicaId;
054    }
055
056
057    /**
058     * Returns a new {@link Csn}.
059     * Generated CSN can be duplicate if user generates CSNs more than 2G 
060     * times a milliseconds.
061     * 
062     * @return The new generated CSN 
063     */
064    public Csn newInstance()
065    {
066        int tmpChangeCount;
067
068        synchronized ( lock )
069        {
070            long newTimestamp = System.currentTimeMillis();
071
072            // We will be able to generate 2 147 483 647 CSNs each 10 ms max
073            if ( lastTimestamp == newTimestamp )
074            {
075                changeCount++;
076            }
077            else
078            {
079                lastTimestamp = newTimestamp;
080                changeCount = 0;
081            }
082
083            tmpChangeCount = changeCount;
084        }
085
086        return new Csn( lastTimestamp, tmpChangeCount, replicaId, 0 );
087    }
088
089
090    /**
091     * Returns a new {@link Csn} created from the given values.
092     * 
093     * This method is <b>not</b> to be used except for test purposes.
094     * 
095     * @param timestamp The timestamp to use
096     * @param changeCount The change count to use
097     * @return The new generated CSN 
098     */
099    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}