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Java > Open Source Codes > smallsql > database > FileIndexNode


1 /* =============================================================
2  * SmallSQL : a free Java DBMS library for the Java(tm) platform
3  * =============================================================
4  *
5  * (C) Copyright 2004-2006, by Volker Berlin.
6  *
7  * Project Info: http://www.smallsql.de/
8  *
9  * This library is free software; you can redistribute it and/or modify it
10  * under the terms of the GNU Lesser General Public License as published by
11  * the Free Software Foundation; either version 2.1 of the License, or
12  * (at your option) any later version.
13  *
14  * This library is distributed in the hope that it will be useful, but
15  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
17  * License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with this library; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
22  * USA.
23  *
24  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
25  * in the United States and other countries.]
26  *
27  * ---------------
28  * FileIndexNode.java
29  * ---------------
30  * Author: Volker Berlin
31  *
32  */
33 package smallsql.database;
34
35 import java.io.*;
36 import java.sql.SQLException JavaDoc;
37 /**
38  * @author Volker Berlin
39  *
40  */
41 public class FileIndexNode extends IndexNode {
42
43     private final RandomAccessFile file;
44     private long fileOffset;
45     
46     
47     /**
48      * Create a new Node in the Index.
49      * @param unique descript if it is an unique index (primary key) or a multi value index is.
50      */
51     FileIndexNode(boolean unique, char digit, RandomAccessFile file){
52         super(unique, digit);
53         this.file = file;
54     }
55     
56     
57     protected IndexNode createIndexNode(boolean unique, char digit){
58         return new FileIndexNode(unique, digit, file);
59     }
60     
61     
62     void save() throws Exception JavaDoc{
63         MemoryStream output = new MemoryStream();
64         save(output);
65         file.seek(fileOffset);
66         output.writeTo(file);
67     }
68     
69     void saveRef(MemoryStream output){
70         output.writeLong(fileOffset);
71     }
72     
73     IndexNode readRef( long offset ) throws SQLException JavaDoc{
74         MemoryStream input = new MemoryStream();
75         FileIndexNode node = new FileIndexNode( getUnique(), (char)input.readShort(), file );
76         node.fileOffset = offset;
77         load( input );
78         return node;
79     }
80 }
81
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