/*
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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 legal-notices/CDDLv1_0.txt
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* or http://forgerock.org/license/CDDLv1.0.html.
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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 legal-notices/CDDLv1_0.txt.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* 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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* Copyright 2008-2010 Sun Microsystems, Inc.
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* Portions Copyright 2015 ForgeRock AS
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*/
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package org.opends.server.replication.plugin;
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import java.util.zip.Checksum;
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/**
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* This class computes the generation id used for a replication domain.
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* It is a checksum based on some special entries/attributes of the domain.
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* The written stream to this class is the LDIF representation of the entries
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* we are interested in for computing the generation id. The current
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* implementation simply does the sum of each written byte and stores the value
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* in a long. We do not care about the cycling long as the probability of 2
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* data sets having the same checksum is very low.
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*/
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public class GenerationIdChecksum implements Checksum
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{
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/** Checksum to be returned. */
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private long checksum;
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/** This is the generation id for an empty backend. */
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public static final long EMPTY_BACKEND_GENERATION_ID = 48L;
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/** Update the checksum with one added byte. */
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private void updateWithOneByte(byte b)
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{
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/*
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* The "end of line" code is CRLF under windows but LF on UNIX. So to get
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* the same checksum value on every platforms, we always exclude the CR and
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* LF characters from the computation.
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*/
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if (b != 0x0D && b != 0x0A) // CR=0D and LF=0A
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{
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checksum += b;
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}
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}
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/** {@inheritDoc} */
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public void update(int b)
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{
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updateWithOneByte((byte) b);
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}
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/** {@inheritDoc} */
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public void update(byte[] b, int off, int len)
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{
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for (int i = off; i < off + len; i++)
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{
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updateWithOneByte(b[i]);
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}
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}
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/** {@inheritDoc} */
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public long getValue()
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{
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if (checksum != 0L)
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{
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return checksum;
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} else
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{
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/*
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* Computing an empty backend writes the number of entries (0) only,
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* will not be added to the checksum as no entries will follow. To treat
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* this special case, and to keep consistency with old versions, in that
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* case we hardcode and return the generation id value for an empty
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* backend.
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*/
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return EMPTY_BACKEND_GENERATION_ID;
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}
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}
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/** {@inheritDoc} */
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public void reset()
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{
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checksum = 0L;
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}
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}
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