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 }