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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 across one or more entire separate pages of
* page type USAGE_MAP. This type of map can contain 32736 pages per reference
* page, and a maximum of 16 reference map pages for a total maximum of 523776
* pages (2 GB).
* @author Tim McCune
*/
public class ReferenceUsageMap extends UsageMap {
/** Buffer that contains the current reference map page */
private ByteBuffer _mapPageBuffer;
/** Page number of the reference map page that was last read */
private int _mapPageNum;
/**
* @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 ReferenceUsageMap(PageChannel pageChannel, ByteBuffer dataBuffer,
int pageNum, JetFormat format, short rowStart)
throws IOException
{
super(pageChannel, dataBuffer, pageNum, format, rowStart);
_mapPageBuffer = pageChannel.createPageBuffer();
for (int i = 0; i < 17; i++) {
_mapPageNum = dataBuffer.getInt(getRowStart() +
format.OFFSET_REFERENCE_MAP_PAGE_NUMBERS + (4 * i));
if (_mapPageNum > 0) {
pageChannel.readPage(_mapPageBuffer, _mapPageNum);
byte pageType = _mapPageBuffer.get();
if (pageType != PageTypes.USAGE_MAP) {
throw new IOException("Looking for usage map at page " + _mapPageNum +
", but page type is " + pageType);
}
_mapPageBuffer.position(format.OFFSET_USAGE_MAP_PAGE_DATA);
setStartOffset(_mapPageBuffer.position());
processMap(_mapPageBuffer, i, 0);
}
}
}
//Javadoc copied from UsageMap
protected void addOrRemovePageNumber(final int pageNumber, boolean add)
throws IOException
{
int pageIndex = (int) Math.floor(pageNumber / getFormat().PAGES_PER_USAGE_MAP_PAGE);
int mapPageNumber = getDataBuffer().getInt(calculateMapPagePointerOffset(pageIndex));
if (mapPageNumber > 0) {
if (_mapPageNum != mapPageNumber) {
//Need to read in the map page
getPageChannel().readPage(_mapPageBuffer, mapPageNumber);
_mapPageNum = mapPageNumber;
}
} else {
//Need to create a new usage map page
createNewUsageMapPage(pageIndex);
}
updateMap(pageNumber, pageNumber - (getFormat().PAGES_PER_USAGE_MAP_PAGE * pageIndex),
1 << ((pageNumber - (getFormat().PAGES_PER_USAGE_MAP_PAGE * pageIndex)) % 8),
_mapPageBuffer, add);
getPageChannel().writePage(_mapPageBuffer, _mapPageNum);
}
/**
* Create a new usage map page and update the map declaration with a pointer
* to it.
* @param pageIndex Index of the page reference within the map declaration
*/
private void createNewUsageMapPage(int pageIndex) throws IOException {
_mapPageBuffer = getPageChannel().createPageBuffer();
_mapPageBuffer.put(PageTypes.USAGE_MAP);
_mapPageBuffer.put((byte) 0x01); //Unknown
_mapPageBuffer.putShort((short) 0); //Unknown
_mapPageNum = getPageChannel().writeNewPage(_mapPageBuffer);
getDataBuffer().putInt(calculateMapPagePointerOffset(pageIndex), _mapPageNum);
getPageChannel().writePage(getDataBuffer(), getDataPageNumber());
}
private int calculateMapPagePointerOffset(int pageIndex) {
return getRowStart() + getFormat().OFFSET_REFERENCE_MAP_PAGE_NUMBERS + (pageIndex * 4);
}
}
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