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: FreeLogicalRowIdPageManager.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $ 46 */ 47 48 package jdbm.recman; 49 50 import java.io.IOException; 51 52 /** 53 * This class manages free Logical rowid pages and provides methods 54 * to free and allocate Logical rowids on a high level. 55 */ 56 final class FreeLogicalRowIdPageManager { 57 // our record file 58 private RecordFile file; 59 // our page manager 60 private PageManager pageman; 61 62 /** 63 * Creates a new instance using the indicated record file and 64 * page manager. 65 */ 66 FreeLogicalRowIdPageManager(RecordFile file, 67 PageManager pageman) throws IOException { 68 this.file = file; 69 this.pageman = pageman; 70 } 71 72 /** 73 * Returns a free Logical rowid, or 74 * null if nothing was found. 75 */ 76 Location get() throws IOException { 77 78 // Loop through the free Logical rowid list until we find 79 // the first rowid. 80 Location retval = null; 81 PageCursor curs = new PageCursor(pageman, Magic.FREELOGIDS_PAGE); 82 while (curs.next() != 0) { 83 FreeLogicalRowIdPage fp = FreeLogicalRowIdPage 84 .getFreeLogicalRowIdPageView(file.get(curs.getCurrent())); 85 int slot = fp.getFirstAllocated(); 86 if (slot != -1) { 87 // got one! 88 retval = 89 new Location(fp.get(slot)); 90 fp.free(slot); 91 if (fp.getCount() == 0) { 92 // page became empty - free it 93 file.release(curs.getCurrent(), false); 94 pageman.free(Magic.FREELOGIDS_PAGE, curs.getCurrent()); 95 } 96 else 97 file.release(curs.getCurrent(), true); 98 99 return retval; 100 } 101 else { 102 // no luck, go to next page 103 file.release(curs.getCurrent(), false); 104 } 105 } 106 return null; 107 } 108 109 /** 110 * Puts the indicated rowid on the free list 111 */ 112 void put(Location rowid) 113 throws IOException { 114 115 PhysicalRowId free = null; 116 PageCursor curs = new PageCursor(pageman, Magic.FREELOGIDS_PAGE); 117 long freePage = 0; 118 while (curs.next() != 0) { 119 freePage = curs.getCurrent(); 120 BlockIo curBlock = file.get(freePage); 121 FreeLogicalRowIdPage fp = FreeLogicalRowIdPage 122 .getFreeLogicalRowIdPageView(curBlock); 123 int slot = fp.getFirstFree(); 124 if (slot != -1) { 125 free = fp.alloc(slot); 126 break; 127 } 128 129 file.release(curBlock); 130 } 131 if (free == null) { 132 // No more space on the free list, add a page. 133 freePage = pageman.allocate(Magic.FREELOGIDS_PAGE); 134 BlockIo curBlock = file.get(freePage); 135 FreeLogicalRowIdPage fp = 136 FreeLogicalRowIdPage.getFreeLogicalRowIdPageView(curBlock); 137 free = fp.alloc(0); 138 } 139 free.setBlock(rowid.getBlock()); 140 free.setOffset(rowid.getOffset()); 141 file.release(freePage, true); 142 } 143 }