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Java > Open Source Codes > smallsql > database > ExpressionFunctionSubstring


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  * ExpressionFunctionSubstring.java
29  * ---------------
30  * Author: Volker Berlin
31  *
32  * Created on 23.06.2004
33  */

34 package smallsql.database;
35
36
37 /**
38  * @author Volker Berlin
39  */

40 final class ExpressionFunctionSubstring extends ExpressionFunctionReturnP1StringAndBinary {
41
42
43     final int getFunction() {
44         return SQLTokenizer.SUBSTRING;
45     }
46
47
48     final boolean isNull() throws Exception JavaDoc {
49         return param1.isNull() || param2.isNull() || param3.isNull();
50     }
51
52
53     final byte[] getBytes() throws Exception JavaDoc{
54         if(isNull()) return null;
55         byte[] bytes = param1.getBytes();
56         int byteLen = bytes.length;
57         int start = Math.min( Math.max( 0, param2.getInt() - 1), byteLen);
58         int length = param3.getInt();
59         if(length < 0)
60             throw Utils.createSQLException("Invalid length '"+length + "' in function SUBSTRING");
61         if(start == 0 && byteLen == length) return bytes;
62         if(byteLen > length + start){
63             byte[] b = new byte[length];
64             System.arraycopy(bytes, start, b, 0, length);
65             return b;
66         }else{
67             byte[] b = new byte[byteLen - start];
68             System.arraycopy(bytes, start, b, 0, b.length);
69             return b;
70         }
71     }
72     
73     
74     final String JavaDoc getString() throws Exception JavaDoc {
75         if(isNull()) return null;
76         String JavaDoc str = param1.getString();
77         int strLen = str.length();
78         int start = Math.min( Math.max( 0, param2.getInt() - 1), strLen);
79         int length = param3.getInt();
80         if(length < 0)
81             throw Utils.createSQLException("Invalid length '"+length + "' in function SUBSTRING");
82         length = Math.min( length, strLen-start );
83         return str.substring(start, start+length);
84     }
85
86
87 }
88
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