| /** |
| * 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); |
| } |
| } |