/**
* JDBM LICENSE v1.00
*
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided
* that the following conditions are met:
*
* 1. Redistributions of source code must retain copyright
* statements and notices. Redistributions must also contain a
* copy of this document.
*
* 2. Redistributions in binary form must reproduce the
* above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* 3. The name "JDBM" must not be used to endorse or promote
* products derived from this Software without prior written
* permission of Cees de Groot. For written permission,
* please contact cg@cdegroot.com.
*
* 4. Products derived from this Software may not be called "JDBM"
* nor may "JDBM" appear in their names without prior written
* permission of Cees de Groot.
*
* 5. Due credit should be given to the JDBM Project
* (http://jdbm.sourceforge.net/).
*
* THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
* NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright 2000 (C) Cees de Groot. All Rights Reserved.
* Contributions are Copyright (C) 2000 by their associated contributors.
*
* $Id: DataPage.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $
*/
package jdbm.recman;
/**
* Class describing a page that holds data.
*/
final class DataPage extends PageHeader {
// offsets
private static final short O_FIRST = PageHeader.SIZE; // short firstrowid
static final short O_DATA = (short)(O_FIRST + Magic.SZ_SHORT);
static final short DATA_PER_PAGE = (short)(RecordFile.BLOCK_SIZE - O_DATA);
/**
* Constructs a data page view from the indicated block.
*/
DataPage(BlockIo block) {
super(block);
}
/**
* Factory method to create or return a data page for the
* indicated block.
*/
static DataPage getDataPageView(BlockIo block) {
BlockView view = block.getView();
if (view != null && view instanceof DataPage)
return (DataPage) view;
else
return new DataPage(block);
}
/** Returns the first rowid's offset */
short getFirst() {
return block.readShort(O_FIRST);
}
/** Sets the first rowid's offset */
void setFirst(short value) {
paranoiaMagicOk();
if (value > 0 && value < O_DATA)
throw new Error("DataPage.setFirst: offset " + value
+ " too small");
block.writeShort(O_FIRST, value);
}
}
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