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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SubstringFunction.java,v 1.7 2005/01/14 02:22:00 elharo Exp $
3    * $Revision: 1.7 $
4    * $Date: 2005/01/14 02:22:00 $
5    *
6    * ====================================================================
7    *
8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9    * All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions
13   * are met:
14   *
15   * 1. Redistributions of source code must retain the above copyright
16   *    notice, this list of conditions, and the following disclaimer.
17   *
18   * 2. Redistributions in binary form must reproduce the above copyright
19   *    notice, this list of conditions, and the disclaimer that follows
20   *    these conditions in the documentation and/or other materials
21   *    provided with the distribution.
22   *
23   * 3. The name "Jaxen" must not be used to endorse or promote products
24   *    derived from this software without prior written permission.  For
25   *    written permission, please contact license@jaxen.org.
26   *
27   * 4. Products derived from this software may not be called "Jaxen", nor
28   *    may "Jaxen" appear in their name, without prior written permission
29   *    from the Jaxen Project Management (pm@jaxen.org).
30   *
31   * In addition, we request (but do not require) that you include in the
32   * end-user documentation provided with the redistribution and/or in the
33   * software itself an acknowledgement equivalent to the following:
34   *     "This product includes software developed by the
35   *      Jaxen Project (http://www.jaxen.org/)."
36   * Alternatively, the acknowledgment may be graphical using the logos
37   * available at http://www.jaxen.org/
38   *
39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50   * SUCH DAMAGE.
51   *
52   * ====================================================================
53   * This software consists of voluntary contributions made by many
54   * individuals on behalf of the Jaxen Project and was originally
55   * created by bob mcwhirter <bob@werken.com> and
56   * James Strachan <jstrachan@apache.org>.  For more information on the
57   * Jaxen Project, please see <http://www.jaxen.org/>.
58   *
59   */
60  package org.jaxen.function;
61  
62  import java.util.List;
63  
64  import org.jaxen.Context;
65  import org.jaxen.Function;
66  import org.jaxen.FunctionCallException;
67  import org.jaxen.Navigator;
68  /***
69   * <p><b>4.2</b> <code><i>string</i> substring(<i>string</i>,<i>number</i>,<i>number?</i>)</code>
70   *
71   * @author bob mcwhirter (bob @ werken.com)
72   * @see "http://www.w3.org/TR/xpath#function-substring"
73   */
74  public class SubstringFunction implements Function
75  {
76      public Object call(Context context,
77                         List args) throws FunctionCallException
78      {
79          final int argc = args.size();
80          if (argc < 2 || argc > 3){
81              throw new FunctionCallException( "substring() requires two or three arguments." );
82          }
83  
84          final Navigator nav = context.getNavigator();
85  
86          final String str = StringFunction.evaluate(args.get(0), nav );
87          // The spec doesn't really address this case
88          if (str == null){
89              return "";
90          }
91  
92          final int strlen = str.length();
93  
94          if (strlen == 0){
95              return "";
96          }
97  
98          Double d1 = NumberFunction.evaluate(args.get(1), nav);
99  
100         if (d1.isNaN()){
101             return "";
102         }
103         // Round the value and subtract 1 as Java strings are zero based
104         int start = RoundFunction.evaluate(d1, nav).intValue() - 1;
105 
106         int len = strlen;
107         if (argc == 3){
108             Double d2 = NumberFunction.evaluate(args.get(2), nav);
109 
110             if (!d2.isNaN()){
111                 len = RoundFunction.evaluate(d2, nav ).intValue();
112             }
113             else {
114                 len = 0;
115             }
116         }
117 
118         int end = start + len;
119 
120         // negative start is treated as 0
121         if ( start < 0){
122             start = 0;
123         }else if (start > strlen){
124             return "";
125         }
126 
127         if (end > strlen){
128             end = strlen;
129         }
130         return str.substring(start, end);
131     }
132 }