KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > jaxen > function > StringLengthFunction


1 /*
2  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/StringLengthFunction.java,v 1.9 2005/06/26 16:07:22 elharo Exp $
3  * $Revision: 1.9 $
4  * $Date: 2005/06/26 16:07:22 $
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  * $Id: StringLengthFunction.java,v 1.9 2005/06/26 16:07:22 elharo Exp $
60  */
61
62
63 package org.jaxen.function;
64
65 import java.util.List JavaDoc;
66
67 import org.jaxen.Context;
68 import org.jaxen.Function;
69 import org.jaxen.FunctionCallException;
70 import org.jaxen.Navigator;
71
72 /**
73  * <p><b>4.2</b> <code><i>number</i> string-length(<i>string</i>)</code></p>
74  *
75  * <p>
76  * The <b>string-length</b> function returns the number of <strong>Unicode characters</strong>
77  * in its argument. This is <strong>not</strong> necessarily
78  * the same as the number <strong>Java chars</strong>
79  * in the corresponding Java string. In particular, if the Java <code>String</code>
80  * contains surrogate pairs each such pair will be counted as only one character
81  * by this function. If the argument is omitted,
82  * it returns the length of the string-value of the context node.
83  * </p>
84  *
85  * @author bob mcwhirter (bob @ werken.com)
86  * @see <a HREF="http://www.w3.org/TR/xpath#function-string-length" target="_top">Section
87  * 4.2 of the XPath Specification</a>
88  */
89 public class StringLengthFunction implements Function
90 {
91
92     
93     /**
94      * Create a new <code>StringLengthFunction</code> object.
95      */
96     public StringLengthFunction() {}
97     
98     
99     /**
100      * <p>
101      * Returns the number of Unicode characters in the string-value of the argument.
102      * </p>
103      *
104      * @param context the context at the point in the
105      * expression when the function is called
106      * @param args a list containing the item whose string-value is to be counted.
107      * If empty, the length of the context node's string-value is returned.
108      *
109      * @return a <code>Double</code> giving the number of Unicode characters
110      *
111      * @throws FunctionCallException if args has more than one item
112      */
113     public Object JavaDoc call(Context context,
114                        List JavaDoc args) throws FunctionCallException
115     {
116         if (args.size() == 0)
117         {
118             return evaluate( context.getNodeSet(),
119                              context.getNavigator() );
120         }
121         else if (args.size() == 1)
122         {
123             return evaluate( args.get(0),
124                              context.getNavigator() );
125         }
126
127         throw new FunctionCallException( "string-length() requires one argument." );
128     }
129
130     /**
131      * <p>
132      * Returns the number of Unicode characters in the string-value of
133      * an object.
134      * </p>
135      *
136      * @param obj the object whose string-value is counted
137      * @param nav used to calculate the string-values of the first two arguments
138      *
139      * @return a <code>Double</code> giving the number of Unicode characters
140      *
141      * @throws FunctionCallException if the string contains mismatched surrogates
142      */
143     public static Double JavaDoc evaluate(Object JavaDoc obj, Navigator nav) throws FunctionCallException
144     {
145         
146         // could/should I push the mismnatching checks into StringFunction.evaluate()????
147 String JavaDoc str = StringFunction.evaluate( obj, nav );
148         // String.length() counts UTF-16 code points; not Unicode characters
149 char[] data = str.toCharArray();
150         int length = 0;
151         for (int i = 0; i < data.length; i++) {
152             char c = data[i];
153             length++;
154             // if this is a high surrogate; assume the next character is
155 // is a low surrogate and skip it
156 if (c >= 0xD800) {
157                 try {
158                     char low = data[i+1];
159                     if (low < 0xDC00 || low > 0xDFFF) {
160                         throw new FunctionCallException("Bad surrogate pair in string " + str);
161                     }
162                     i++; // increment past low surrogate
163 }
164                 catch (ArrayIndexOutOfBoundsException JavaDoc ex) {
165                     throw new FunctionCallException("Bad surrogate pair in string " + str);
166                 }
167             }
168         }
169         return new Double JavaDoc(length);
170     }
171     
172 }
173
Popular Tags