/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at
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* trunk/opends/resource/legal-notices/OpenDS.LICENSE
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* or https://OpenDS.dev.java.net/OpenDS.LICENSE.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at
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* trunk/opends/resource/legal-notices/OpenDS.LICENSE. If applicable,
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* add the following below this CDDL HEADER, with the fields enclosed
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* by brackets "[]" replaced with your own identifying * information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Portions Copyright 2006 Sun Microsystems, Inc.
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*/
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package org.opends.server.synchronization;
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import org.opends.server.util.TimeThread;
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/**
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* This class defines a structure that is used for storing the
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* last change numbers generated on this server or received from other servers
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* and generating new changenumbers that are guaranteed to be larger than
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* all the previously seen or generated change numbers.
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*/
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public class ChangeNumberGenerator
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{
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private long lastTime;
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private int seqnum = 0;
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private short serverId;
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/**
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* Create a new ChangeNumber Generator.
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* @param id id to use when creating change numbers
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* @param timestamp time to start with
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*/
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public ChangeNumberGenerator(short id, long timestamp)
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{
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lastTime = timestamp;
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serverId = id;
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}
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/**
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* Generate a new ChangeNumber.
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*
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* @return the generated ChangeNUmber
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*/
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public ChangeNumber NewChangeNumber()
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{
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/* TODO : we probably don't need a time stamp with a 1 msec accuracy */
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long curTime = TimeThread.getTime();
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synchronized(this)
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{
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if (curTime > lastTime)
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{
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seqnum = 0;
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lastTime = curTime;
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}
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else
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{
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seqnum++;
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if (seqnum > 0xFFFF)
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{
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lastTime++;
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seqnum = 0;
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}
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}
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}
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return new ChangeNumber(lastTime, seqnum, serverId);
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}
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/**
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* Adjust the lastTime and seqnum of this Changenumber generator with
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* a ChangeNumber that we have received from another server.
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* This is necessary because we need that the changenumber generated
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* after processing an update received from other hosts to be larger
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* than the received changenumber
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*
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* @param number the ChangeNumber to adjust with
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*/
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public void adjust(ChangeNumber number)
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{
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long rcvdTime = number.getTime();
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int rcvdSeqnum = number.getSeqnum();
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/* need to synchronize with NewChangeNumber method so that we
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* protect writing of seqnum and lastTime fields
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*/
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synchronized(this)
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{
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if (lastTime > rcvdTime)
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return;
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if (lastTime == rcvdTime)
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{
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if (seqnum < rcvdSeqnum)
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{
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seqnum = rcvdSeqnum;
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}
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return;
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}
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if (lastTime < rcvdTime)
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{
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lastTime = rcvdTime;
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seqnum = rcvdSeqnum;
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}
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}
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}
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}
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