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: RecordHeader.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $
46 */
47
48 package jdbm.recman;
49
50 /**
51 * The data that comes at the start of a record of data. It stores
52 * both the current size and the avaliable size for the record - the latter
53 * can be bigger than the former, which allows the record to grow without
54 * needing to be moved and which allows the system to put small records
55 * in larger free spots.
56 */
57 class RecordHeader {
58 // offsets
59 private static final short O_CURRENTSIZE = 0; // int currentSize
60 private static final short O_AVAILABLESIZE = Magic.SZ_INT; // int availableSize
61 static final int SIZE = O_AVAILABLESIZE + Magic.SZ_INT;
62
63 // my block and the position within the block
64 private BlockIo block;
65 private short pos;
66
67 /**
68 * Constructs a record header from the indicated data starting at
69 * the indicated position.
70 */
71 RecordHeader(BlockIo block, short pos) {
72 this.block = block;
73 this.pos = pos;
74 if (pos > (RecordFile.BLOCK_SIZE - SIZE))
75 throw new Error("Offset too large for record header ("
76 + block.getBlockId() + ":"
77 + pos + ")");
78 }
79
80 /** Returns the current size */
81 int getCurrentSize() {
82 return block.readInt(pos + O_CURRENTSIZE);
83 }
84
85 /** Sets the current size */
86 void setCurrentSize(int value) {
87 block.writeInt(pos + O_CURRENTSIZE, value);
88 }
89
90 /** Returns the available size */
91 int getAvailableSize() {
92 return block.readInt(pos + O_AVAILABLESIZE);
93 }
94
95 /** Sets the available size */
96 void setAvailableSize(int value) {
97 block.writeInt(pos + O_AVAILABLESIZE, value);
98 }
99
100 // overrides java.lang.Object
101 public String toString() {
102 return "RH(" + block.getBlockId() + ":" + pos
103 + ", avl=" + getAvailableSize()
104 + ", cur=" + getCurrentSize()
105 + ")";
106 }
107 }