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/*
Copyright (c) 2005 Health Market Science, Inc.
This library 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 2.1 of the License, or (at your option) any later version.
This library 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 library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA
You can contact Health Market Science at info@healthmarketscience.com
or at the following address:
Health Market Science
2700 Horizon Drive
Suite 200
King of Prussia, PA 19406
*/
package com.healthmarketscience.jackcess;
import java.io.IOException;
import java.nio.ByteBuffer;
/**
* Usage map whose map is written inline in the same page. This type of map
* can contain a maximum of 512 pages, and is always used for free space maps.
* It has a start page, which all page numbers in its map are calculated as
* starting from.
* @author Tim McCune
*/
public class InlineUsageMap extends UsageMap {
/** Size in bytes of the map */
private static final int MAP_SIZE = 64;
/** First page that this usage map applies to */
private int _startPage = 0;
/**
* @param pageChannel Used to read in pages
* @param dataBuffer Buffer that contains this map's declaration
* @param pageNum Page number that this usage map is contained in
* @param format Format of the database that contains this usage map
* @param rowStart Offset at which the declaration starts in the buffer
*/
public InlineUsageMap(PageChannel pageChannel, ByteBuffer dataBuffer,
int pageNum, JetFormat format, short rowStart)
throws IOException
{
super(pageChannel, dataBuffer, pageNum, format, rowStart);
_startPage = dataBuffer.getInt(rowStart + 1);
processMap(dataBuffer, 0, _startPage);
}
//Javadoc copied from UsageMap
protected void addOrRemovePageNumber(final int pageNumber, boolean add)
throws IOException
{
if (add && pageNumber < _startPage) {
throw new IOException("Can't add page number " + pageNumber +
" because it is less than start page " + _startPage);
}
int relativePageNumber = pageNumber - _startPage;
ByteBuffer buffer = getDataBuffer();
if ((!add && !getPageNumbers().remove(new Integer(pageNumber))) || (add &&
(relativePageNumber > MAP_SIZE * 8 - 1)))
{
//Increase the start page to the current page and clear out the map.
_startPage = pageNumber;
buffer.position(getRowStart() + 1);
buffer.putInt(_startPage);
getPageNumbers().clear();
if (!add) {
for (int j = 0; j < MAP_SIZE; j++) {
buffer.put((byte) 0xff); //Fill bitmap with 1s
}
for (int j = _startPage; j < _startPage + MAP_SIZE * 8; j++) {
getPageNumbers().add(new Integer(j)); //Fill our list with page numbers
}
}
getPageChannel().writePage(buffer, getDataPageNumber());
relativePageNumber = pageNumber - _startPage;
}
updateMap(pageNumber, relativePageNumber, 1 << (relativePageNumber % 8), buffer, add);
//Write the updated map back to disk
getPageChannel().writePage(buffer, getDataPageNumber());
}
}
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