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 }