1 /** 2 * JDBM LICENSE v1.00 3 * 4 * Redistribution and use of this software and associated documentation 5 * ("Software"), with or without modification, are permitted provided 6 * that the following conditions are met: 7 * 8 * 1. Redistributions of source code must retain copyright 9 * statements and notices. Redistributions must also contain a 10 * copy of this document. 11 * 12 * 2. Redistributions in binary form must reproduce the 13 * above copyright notice, this list of conditions and the 14 * following disclaimer in the documentation and/or other 15 * materials provided with the distribution. 16 * 17 * 3. The name "JDBM" must not be used to endorse or promote 18 * products derived from this Software without prior written 19 * permission of Cees de Groot. For written permission, 20 * please contact cg@cdegroot.com. 21 * 22 * 4. Products derived from this Software may not be called "JDBM" 23 * nor may "JDBM" appear in their names without prior written 24 * permission of Cees de Groot. 25 * 26 * 5. Due credit should be given to the JDBM Project 27 * (http://jdbm.sourceforge.net/). 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS 30 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT 31 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 32 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 33 * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 34 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 35 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 36 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 38 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 39 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 40 * OF THE POSSIBILITY OF SUCH DAMAGE. 41 * 42 * Copyright 2000 (C) Cees de Groot. All Rights Reserved. 43 * Contributions are Copyright (C) 2000 by their associated contributors. 44 * 45 * $Id: TranslationPage.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $ 46 */ 47 48 package jdbm.recman; 49 50 /** 51 * Class describing a page that holds translations from physical rowids 52 * to logical rowids. In fact, the page just holds physical rowids - the 53 * page's block is the block for the logical rowid, the offset serve 54 * as offset for the rowids. 55 */ 56 final class TranslationPage extends PageHeader { 57 // offsets 58 static final short O_TRANS = PageHeader.SIZE; // short count 59 static final short ELEMS_PER_PAGE = 60 (RecordFile.BLOCK_SIZE - O_TRANS) / PhysicalRowId.SIZE; 61 62 // slots we returned. 63 final PhysicalRowId[] slots = new PhysicalRowId[ELEMS_PER_PAGE]; 64 65 /** 66 * Constructs a data page view from the indicated block. 67 */ 68 TranslationPage(BlockIo block) { 69 super(block); 70 } 71 72 /** 73 * Factory method to create or return a data page for the 74 * indicated block. 75 */ 76 static TranslationPage getTranslationPageView(BlockIo block) { 77 BlockView view = block.getView(); 78 if (view != null && view instanceof TranslationPage) 79 return (TranslationPage) view; 80 else 81 return new TranslationPage(block); 82 } 83 84 /** Returns the value of the indicated rowid on the page */ 85 PhysicalRowId get(short offset) { 86 int slot = (offset - O_TRANS) / PhysicalRowId.SIZE; 87 if (slots[slot] == null) 88 slots[slot] = new PhysicalRowId(block, offset); 89 return slots[slot]; 90 } 91 }