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/**
* 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: TranslationPage.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $
*/
package jdbm.recman;
/**
* Class describing a page that holds translations from physical rowids
* to logical rowids. In fact, the page just holds physical rowids - the
* page's block is the block for the logical rowid, the offset serve
* as offset for the rowids.
*/
final class TranslationPage extends PageHeader
{
// offsets
static final short O_TRANS = PageHeader.SIZE; // short count
static final short ELEMS_PER_PAGE = ( RecordFile.BLOCK_SIZE - O_TRANS ) / PhysicalRowId.SIZE;
// slots we returned.
final PhysicalRowId[] slots = new PhysicalRowId[ELEMS_PER_PAGE];
/**
* Constructs a data page view from the indicated block.
*/
TranslationPage( BlockIo block )
{
super( block );
}
/**
* Factory method to create or return a data page for the indicated block.
*/
static TranslationPage getTranslationPageView( BlockIo block )
{
BlockView view = block.getView();
if ( view != null && view instanceof TranslationPage )
{
return ( TranslationPage ) view;
}
else
{
return new TranslationPage( block );
}
}
/** Returns the value of the indicated rowid on the page */
PhysicalRowId get( short offset )
{
int slot = ( offset - O_TRANS ) / PhysicalRowId.SIZE;
if ( slots[slot] == null )
{
slots[slot] = new PhysicalRowId( block, offset );
}
return slots[slot];
}
}