| /** |
| * 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]; |
| } |
| } |