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: FreePhysicalRowIdPageManager.java,v 1.2 2001/11/17 16:14:25 boisvert Exp $ 46 */ 47 48 package jdbm.recman; 49 50 import java.io.IOException; 51 52 /** 53 * This class manages free physical rowid pages and provides methods 54 * to free and allocate physical rowids on a high level. 55 */ 56 final class FreePhysicalRowIdPageManager 57 { 58 // our record file 59 protected RecordFile _file; 60 61 // our page manager 62 protected PageManager _pageman; 63 64 /** 65 * Creates a new instance using the indicated record file and 66 * page manager. 67 */ 68 FreePhysicalRowIdPageManager( RecordFile file, PageManager pageman ) 69 throws IOException 70 { 71 _file = file; 72 _pageman = pageman; 73 } 74 75 76 /** 77 * Returns a free physical rowid of the indicated size, or 78 * null if nothing was found. 79 */ 80 Location get( int size ) 81 throws IOException 82 { 83 // Loop through the free physical rowid list until we find 84 // a rowid that's large enough. 85 Location retval = null; 86 PageCursor curs = new PageCursor( _pageman, Magic.FREEPHYSIDS_PAGE ); 87 88 while (curs.next() != 0) { 89 FreePhysicalRowIdPage fp = FreePhysicalRowIdPage 90 .getFreePhysicalRowIdPageView( _file.get( curs.getCurrent() ) ); 91 int slot = fp.getFirstLargerThan( size ); 92 if ( slot != -1 ) { 93 // got one! 94 retval = new Location( fp.get( slot ) ); 95 96 int slotsize = fp.get( slot ).getSize(); 97 fp.free( slot ); 98 if ( fp.getCount() == 0 ) { 99 // page became empty - free it 100 _file.release( curs.getCurrent(), false ); 101 _pageman.free( Magic.FREEPHYSIDS_PAGE, curs.getCurrent() ); 102 } else { 103 _file.release( curs.getCurrent(), true ); 104 } 105 106 return retval; 107 } else { 108 // no luck, go to next page 109 _file.release( curs.getCurrent(), false ); 110 } 111 112 } 113 return null; 114 } 115 116 /** 117 * Puts the indicated rowid on the free list 118 */ 119 void put(Location rowid, int size) 120 throws IOException { 121 122 FreePhysicalRowId free = null; 123 PageCursor curs = new PageCursor(_pageman, Magic.FREEPHYSIDS_PAGE); 124 long freePage = 0; 125 while (curs.next() != 0) { 126 freePage = curs.getCurrent(); 127 BlockIo curBlock = _file.get(freePage); 128 FreePhysicalRowIdPage fp = FreePhysicalRowIdPage 129 .getFreePhysicalRowIdPageView(curBlock); 130 int slot = fp.getFirstFree(); 131 if (slot != -1) { 132 free = fp.alloc(slot); 133 break; 134 } 135 136 _file.release(curBlock); 137 } 138 if (free == null) { 139 // No more space on the free list, add a page. 140 freePage = _pageman.allocate(Magic.FREEPHYSIDS_PAGE); 141 BlockIo curBlock = _file.get(freePage); 142 FreePhysicalRowIdPage fp = 143 FreePhysicalRowIdPage.getFreePhysicalRowIdPageView(curBlock); 144 free = fp.alloc(0); 145 } 146 147 free.setBlock(rowid.getBlock()); 148 free.setOffset(rowid.getOffset()); 149 free.setSize(size); 150 _file.release(freePage, true); 151 } 152 }