/*
* eXist Open Source Native XML Database
* Copyright (C) 2001-04 The eXist Project
* http://exist-db.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id$
*/
package org.exist.storage.journal;
/**
* Log Sequence Number: identifies a log record within the journal file.
* A LSN is represented by a Java long and consists of the file number
* of the journal file and an offset into the file.
*
* @author wolf
*/
public class Lsn {
public static final long LSN_INVALID = -1;
private static final long INT_MASK = 0xFFFFFFFFL;
public static long create(int fileNumber, int offset) {
return offset & INT_MASK | ((fileNumber & INT_MASK) << 32);
}
/**
* Returns the file number encoded in the passed LSN.
*
* @param lsn
* @return file number
*/
public static long getFileNumber(long lsn) {
return (lsn >> 32) & INT_MASK;
}
/**
* Returns the file offset encoded in the passed LSN.
*
* @param lsn
* @return file offset
*/
public static long getOffset(long lsn) {
return (lsn & INT_MASK);
}
public static String dump(long lsn) {
return getFileNumber(lsn) + ", " + getOffset(lsn);
}
}