Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
SubstringFunction |
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1 | /* | |
2 | * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SubstringFunction.java,v 1.16 2006/02/05 21:47:41 elharo Exp $ | |
3 | * $Revision: 1.16 $ | |
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 | * | |
12 | * Redistribution and use in source and binary forms, with or without | |
13 | * modification, are permitted provided that the following conditions are | |
14 | * met: | |
15 | * | |
16 | * * Redistributions of source code must retain the above copyright | |
17 | * notice, this list of conditions and the following disclaimer. | |
18 | * | |
19 | * * Redistributions in binary form must reproduce the above copyright | |
20 | * notice, this list of conditions and the following disclaimer in the | |
21 | * documentation and/or other materials provided with the distribution. | |
22 | * | |
23 | * * Neither the name of the Jaxen Project nor the names of its | |
24 | * contributors may be used to endorse or promote products derived | |
25 | * from this software without specific prior written permission. | |
26 | * | |
27 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS | |
28 | * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED | |
29 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A | |
30 | * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER | |
31 | * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | |
32 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
33 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | |
34 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
35 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | |
36 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | |
37 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
38 | * | |
39 | * ==================================================================== | |
40 | * This software consists of voluntary contributions made by many | |
41 | * individuals on behalf of the Jaxen Project and was originally | |
42 | * created by bob mcwhirter <bob@werken.com> and | |
43 | * James Strachan <jstrachan@apache.org>. For more information on the | |
44 | * Jaxen Project, please see <http://www.jaxen.org/>. | |
45 | * | |
46 | */ | |
47 | package org.jaxen.function; | |
48 | ||
49 | import java.util.List; | |
50 | ||
51 | import org.jaxen.Context; | |
52 | import org.jaxen.Function; | |
53 | import org.jaxen.FunctionCallException; | |
54 | import org.jaxen.Navigator; | |
55 | /** | |
56 | * <p> | |
57 | * <b>4.2</b> | |
58 | * <code><i>string</i> substring(<i>string</i>,<i>number</i>,<i>number?</i>)</code> | |
59 | * </p> | |
60 | * | |
61 | * <blockquote src="http://www.w3.org/TR/xpath"> | |
62 | * <p>The <b>substring</b> function returns the | |
63 | * substring of the first argument starting at the position specified in | |
64 | * the second argument with length specified in the third argument. For | |
65 | * example, | |
66 | * | |
67 | * <code>substring("12345",2,3)</code> returns <code>"234"</code>. | |
68 | * If the third argument is not specified, it returns the substring | |
69 | * starting at the position specified in the second argument and | |
70 | * continuing to the end of the string. For example, | |
71 | * <code>substring("12345",2)</code> returns <code>"2345"</code>. | |
72 | * </p> | |
73 | * | |
74 | * <p> | |
75 | * More precisely, each character in the string (see <a | |
76 | * href="http://www.w3.org/TR/xpath#strings">[<b>3.6 Strings</b>]</a>) is considered to have a | |
77 | * numeric position: the position of the first character is 1, the | |
78 | * position of the second character is 2 and so on. | |
79 | * </p> | |
80 | * | |
81 | * <blockquote> <b>NOTE: </b>This differs from Java and ECMAScript, in | |
82 | * which the <code>String.substring</code> method treats the position | |
83 | * of the first character as 0.</blockquote> | |
84 | * | |
85 | * <p> | |
86 | * The returned substring contains those characters for which the | |
87 | * position of the character is greater than or equal to the rounded | |
88 | * value of the second argument and, if the third argument is specified, | |
89 | * less than the sum of the rounded value of the second argument and the | |
90 | * rounded value of the third argument; the comparisons and addition | |
91 | * used for the above follow the standard IEEE 754 rules; rounding is | |
92 | * done as if by a call to the <b><a href="#function-round">round</a></b> | |
93 | * function. The following examples illustrate various unusual cases: | |
94 | * </p> | |
95 | * | |
96 | * <ul> | |
97 | * | |
98 | * <li> | |
99 | * <p> | |
100 | * <code>substring("12345", 1.5, 2.6)</code> returns | |
101 | * <code>"234"</code> | |
102 | * </p> | |
103 | * </li> | |
104 | * | |
105 | * <li> | |
106 | * <p> | |
107 | * <code>substring("12345", 0, 3)</code> returns <code>"12"</code> | |
108 | * | |
109 | * </p> | |
110 | * </li> | |
111 | * | |
112 | * <li> | |
113 | * <p> | |
114 | * <code>substring("12345", 0 div 0, 3)</code> returns <code>""</code> | |
115 | * </p> | |
116 | * </li> | |
117 | * | |
118 | * <li> | |
119 | * <p>. | |
120 | * <code>substring("12345", 1, 0 div 0)</code> returns | |
121 | * | |
122 | * <code>""</code> | |
123 | * </p> | |
124 | * </li> | |
125 | * | |
126 | * <li> | |
127 | * <p> | |
128 | * <code>substring("12345", -42, 1 div 0)</code> returns | |
129 | * <code>"12345"</code> | |
130 | * </p> | |
131 | * </li> | |
132 | * | |
133 | * <li> | |
134 | * <p> | |
135 | * | |
136 | * <code>substring("12345", -1 div 0, 1 div 0)</code> returns | |
137 | * <code>""</code> </blockquote> | |
138 | * | |
139 | * @author bob mcwhirter (bob @ werken.com) | |
140 | * | |
141 | * @see <a href="http://www.w3.org/TR/xpath#function-substring" | |
142 | * target="_top">Section 4.2 of the XPath Specification</a> | |
143 | */ | |
144 | public class SubstringFunction implements Function | |
145 | { | |
146 | ||
147 | /** | |
148 | * Create a new <code>SubstringFunction</code> object. | |
149 | */ | |
150 | 106 | public SubstringFunction() {} |
151 | ||
152 | ||
153 | /** Returns a substring of an XPath string-value by character index. | |
154 | * | |
155 | * @param context the context at the point in the | |
156 | * expression when the function is called | |
157 | * @param args a list that contains two or three items | |
158 | * | |
159 | * @return a <code>String</code> containing the specifed character subsequence of | |
160 | * the original string or the string-value of the context node | |
161 | * | |
162 | * @throws FunctionCallException if <code>args</code> has more than three | |
163 | * or less than two items | |
164 | */ | |
165 | public Object call(Context context, | |
166 | List args) throws FunctionCallException | |
167 | { | |
168 | 104 | final int argc = args.size(); |
169 | 104 | if (argc < 2 || argc > 3){ |
170 | 4 | throw new FunctionCallException( "substring() requires two or three arguments." ); |
171 | } | |
172 | ||
173 | 100 | final Navigator nav = context.getNavigator(); |
174 | ||
175 | 100 | final String str = StringFunction.evaluate(args.get(0), nav ); |
176 | // The spec doesn't really address this case | |
177 | 100 | if (str == null) { |
178 | 0 | return ""; |
179 | } | |
180 | ||
181 | 100 | final int stringLength = (StringLengthFunction.evaluate(args.get(0), nav )).intValue(); |
182 | ||
183 | 100 | if (stringLength == 0) { |
184 | 2 | return ""; |
185 | } | |
186 | ||
187 | 98 | Double d1 = NumberFunction.evaluate(args.get(1), nav); |
188 | ||
189 | 98 | if (d1.isNaN()){ |
190 | 10 | return ""; |
191 | } | |
192 | // Round the value and subtract 1 as Java strings are zero based | |
193 | 88 | int start = RoundFunction.evaluate(d1, nav).intValue() - 1; |
194 | ||
195 | 88 | int substringLength = stringLength; |
196 | 88 | if (argc == 3){ |
197 | 74 | Double d2 = NumberFunction.evaluate(args.get(2), nav); |
198 | ||
199 | 74 | if (!d2.isNaN()){ |
200 | 64 | substringLength = RoundFunction.evaluate(d2, nav ).intValue(); |
201 | 64 | } |
202 | else { | |
203 | 10 | substringLength = 0; |
204 | } | |
205 | } | |
206 | ||
207 | 88 | if (substringLength < 0) return ""; |
208 | ||
209 | 84 | int end = start + substringLength; |
210 | 84 | if (argc == 2) end = stringLength; |
211 | ||
212 | // negative start is treated as 0 | |
213 | 84 | if ( start < 0){ |
214 | 24 | start = 0; |
215 | 24 | } |
216 | 60 | else if (start > stringLength){ |
217 | 10 | return ""; |
218 | } | |
219 | ||
220 | 74 | if (end > stringLength){ |
221 | 22 | end = stringLength; |
222 | 22 | } |
223 | 52 | else if (end < start) return ""; |
224 | ||
225 | 72 | if (stringLength == str.length()) { |
226 | // easy case; no surrogate pairs | |
227 | 66 | return str.substring(start, end); |
228 | } | |
229 | else { | |
230 | 6 | return unicodeSubstring(str, start, end); |
231 | } | |
232 | ||
233 | } | |
234 | ||
235 | private static String unicodeSubstring(String s, int start, int end) { | |
236 | ||
237 | 6 | StringBuffer result = new StringBuffer(s.length()); |
238 | 22 | for (int jChar = 0, uChar=0; uChar < end; jChar++, uChar++) { |
239 | 16 | char c = s.charAt(jChar); |
240 | 16 | if (uChar >= start) result.append(c); |
241 | 16 | if (c >= 0xD800) { // get the low surrogate |
242 | // ???? we could check here that this is indeed a low surroagte | |
243 | // we could also catch StringIndexOutOfBoundsException | |
244 | 6 | jChar++; |
245 | 6 | if (uChar >= start) result.append(s.charAt(jChar)); |
246 | } | |
247 | } | |
248 | 6 | return result.toString(); |
249 | } | |
250 | } |