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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/LangFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
3    * $Revision: 1.13 $
4    * $Date: 2006/02/05 21:47:41 $
5    *
6    * ====================================================================
7    *
8    * Copyright 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 are
13   * met:
14   * 
15   *   * Redistributions of source code must retain the above copyright
16   *     notice, this list of conditions and the following disclaimer.
17   * 
18   *   * Redistributions in binary form must reproduce the above copyright
19   *     notice, this list of conditions and the following disclaimer in the
20   *     documentation and/or other materials provided with the distribution.
21   * 
22   *   * Neither the name of the Jaxen Project nor the names of its
23   *     contributors may be used to endorse or promote products derived 
24   *     from this software without specific prior written permission.
25   * 
26   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37   *
38   * ====================================================================
39   * This software consists of voluntary contributions made by many 
40   * individuals on behalf of the Jaxen Project and was originally 
41   * created by bob mcwhirter <bob@werken.com> and 
42   * James Strachan <jstrachan@apache.org>.  For more information on the 
43   * Jaxen Project, please see <http://www.jaxen.org/>.
44   * 
45   * $Id: LangFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
46   */
47  
48  
49  package org.jaxen.function;
50  
51  import java.util.Iterator;
52  import java.util.List;
53  
54  import org.jaxen.Context;
55  import org.jaxen.Function;
56  import org.jaxen.FunctionCallException;
57  import org.jaxen.Navigator;
58  import org.jaxen.UnsupportedAxisException;
59  
60  /***
61   * <p>
62   * <b>4.3</b> <code><i>boolean</i> lang(<i>string</i>)</code>
63   * </p>
64   * 
65   * <blockquote src="http://www.w3.org/TR/xpath#function-lang">
66   * <p>
67   * The <b>lang</b> function returns true or false depending on whether
68   * the language of the context node as specified by
69   * <code>xml:lang</code> attributes is the same as or is a sublanguage
70   * of the language specified by the argument string. The language of the
71   * context node is determined by the value of the <code>xml:lang</code>
72   * 
73   * attribute on the context node, or, if the context node has no
74   * <code>xml:lang</code> attribute, by the value of the
75   * <code>xml:lang</code> attribute on the nearest ancestor of the
76   * context node that has an <code>xml:lang</code> attribute. If there
77   * is no such attribute, then <b><a href="#function-lang">lang</a></b>
78   * returns false. If there is such an attribute, then <b><a
79   * href="#function-lang">lang</a></b> returns true if the attribute
80   * value is equal to the argument ignoring case, or if there is some
81   * suffix starting with <code>-</code> such that the attribute value
82   * is equal to the argument ignoring that suffix of the attribute value
83   * and ignoring case. For example, <code>lang("en")</code> would
84   * return true if the context node is any of these five elements:
85   * </p>
86   * 
87   * <pre>
88   *  &lt;para xml:lang=&quot;en&quot;/&gt;
89   *  &lt;div xml:lang=&quot;en&quot;&gt;&lt;para/&gt;&lt;/div&gt;
90   *  &lt;para xml:lang=&quot;EN&quot;/&gt;
91   *  &lt;para xml:lang=&quot;en-us&quot;/&gt;
92   * </pre>
93   * 
94   * </blockquote>
95   * 
96   * @author Attila Szegedi (szegedia @ freemail.hu)
97   * @see <a href="http://www.w3.org/TR/xpath#function-lang"
98   *      target="_top">XPath Specification</a>
99   */
100 public class LangFunction implements Function
101 {
102     private static final String LANG_LOCALNAME = "lang";
103     private static final String XMLNS_URI = 
104         "http://www.w3.org/XML/1998/namespace";
105     
106 
107     /***
108      * Create a new <code>LangFunction</code> object.
109      */
110     public LangFunction() {}
111     
112     
113     /***
114      * <p>
115      * Determines whether or not the context node is written in the language specified
116      * by the XPath string-value of <code>args.get(0)</code>,
117      * as determined by the nearest <code>xml:lang</code> attribute in scope. 
118      * </p>
119      * 
120      * @param context the context in which to evaluate the <code>lang()</code> function
121      * @param args the arguments to the lang function
122      * @return a <code>Boolean</code> indicating whether the context node is written in
123      *     the specified language
124      * @throws FunctionCallException if <code>args</code> does not have length one
125      * 
126      */
127     public Object call(Context context,
128                        List args) throws FunctionCallException
129     {
130         if (args.size() != 1) {
131             throw new FunctionCallException("lang() requires exactly one argument.");   
132         }
133         
134         Object arg = args.get(0);
135             
136         try {
137             return evaluate(context.getNodeSet(), arg, context.getNavigator() );
138         }
139         catch(UnsupportedAxisException e) {
140             throw new FunctionCallException("Can't evaluate lang()", 
141                                                  e);
142         }
143        
144     }
145 
146     private static Boolean evaluate(List contextNodes, Object lang, Navigator nav)
147       throws UnsupportedAxisException
148     {
149         return evaluate(contextNodes.get(0), 
150             StringFunction.evaluate(lang, nav), nav)
151             ? Boolean.TRUE : Boolean.FALSE;
152     }
153 
154     private static boolean evaluate(Object node, String lang, Navigator nav)
155       throws UnsupportedAxisException
156     {
157         
158         Object element = node;
159         if (! nav.isElement(element)) {
160             element = nav.getParentNode(node);
161         }
162         while (element != null && nav.isElement(element)) 
163         {
164             Iterator attrs = nav.getAttributeAxisIterator(element);
165             while(attrs.hasNext())
166             {
167                 Object attr = attrs.next();
168                 if(LANG_LOCALNAME.equals(nav.getAttributeName(attr)) && 
169                    XMLNS_URI.equals(nav.getAttributeNamespaceUri(attr)))
170                 {
171                     return 
172                         isSublang(nav.getAttributeStringValue(attr), lang);
173                 }
174             }
175             element = nav.getParentNode(element);
176         }
177         return false;
178     }
179     
180     private static boolean isSublang(String sublang, String lang)
181     {
182         if(sublang.equalsIgnoreCase(lang))
183         {
184             return true;
185         }
186         int ll = lang.length();
187         return 
188             sublang.length() > ll && 
189             sublang.charAt(ll) == '-' && 
190             sublang.substring(0, ll).equalsIgnoreCase(lang);
191     }
192     
193 }
194