/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
* or http://forgerock.org/license/CDDLv1.0.html.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at legal-notices/CDDLv1_0.txt.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information:
* Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*
*
* Copyright 2008-2010 Sun Microsystems, Inc.
* Portions Copyright 2015 ForgeRock AS
*/
package org.opends.server.replication.plugin;
import java.util.zip.Checksum;
/**
* This class computes the generation id used for a replication domain.
* It is a checksum based on some special entries/attributes of the domain.
* The written stream to this class is the LDIF representation of the entries
* we are interested in for computing the generation id. The current
* implementation simply does the sum of each written byte and stores the value
* in a long. We do not care about the cycling long as the probability of 2
* data sets having the same checksum is very low.
*/
public class GenerationIdChecksum implements Checksum
{
/** Checksum to be returned. */
private long checksum;
/** This is the generation id for an empty backend. */
public static final long EMPTY_BACKEND_GENERATION_ID = 48L;
/** Update the checksum with one added byte. */
private void updateWithOneByte(byte b)
{
/*
* The "end of line" code is CRLF under windows but LF on UNIX. So to get
* the same checksum value on every platforms, we always exclude the CR and
* LF characters from the computation.
*/
if (b != 0x0D && b != 0x0A) // CR=0D and LF=0A
{
checksum += b;
}
}
/** {@inheritDoc} */
public void update(int b)
{
updateWithOneByte((byte) b);
}
/** {@inheritDoc} */
public void update(byte[] b, int off, int len)
{
for (int i = off; i < off + len; i++)
{
updateWithOneByte(b[i]);
}
}
/** {@inheritDoc} */
public long getValue()
{
if (checksum != 0L)
{
return checksum;
} else
{
/*
* Computing an empty backend writes the number of entries (0) only,
* will not be added to the checksum as no entries will follow. To treat
* this special case, and to keep consistency with old versions, in that
* case we hardcode and return the generation id value for an empty
* backend.
*/
return EMPTY_BACKEND_GENERATION_ID;
}
}
/** {@inheritDoc} */
public void reset()
{
checksum = 0L;
}
}