/*
|
* 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.
|
*/
|
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 = 0L;
|
|
/**
|
* 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 += (long) 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, which
|
// 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;
|
}
|
}
|
