org.jaxen.function.SubstringFunction Maven / Gradle / Ivy
/*
* $Header$
* $Revision$
* $Date$
*
* ====================================================================
*
* Copyright 2000-2002 bob mcwhirter & James Strachan.
* All rights reserved.
*
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of the Jaxen Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ====================================================================
* This software consists of voluntary contributions made by many
* individuals on behalf of the Jaxen Project and was originally
* created by bob mcwhirter and
* James Strachan . For more information on the
* Jaxen Project, please see
* 4.2
* string substring(string,number,number?)
*
*
*
* The substring function returns the
* substring of the first argument starting at the position specified in
* the second argument with length specified in the third argument. For
* example,
*
* substring("12345",2,3) returns "234".
* If the third argument is not specified, it returns the substring
* starting at the position specified in the second argument and
* continuing to the end of the string. For example,
* substring("12345",2) returns "2345".
*
*
*
* More precisely, each character in the string (see [3.6 Strings]) is considered to have a
* numeric position: the position of the first character is 1, the
* position of the second character is 2 and so on.
*
*
* NOTE: This differs from Java and ECMAScript, in
* which the String.substring method treats the position
* of the first character as 0.
*
*
* The returned substring contains those characters for which the
* position of the character is greater than or equal to the rounded
* value of the second argument and, if the third argument is specified,
* less than the sum of the rounded value of the second argument and the
* rounded value of the third argument; the comparisons and addition
* used for the above follow the standard IEEE 754 rules; rounding is
* done as if by a call to the round
* function. The following examples illustrate various unusual cases:
*
*
*
*
* -
*
* substring("12345", 1.5, 2.6) returns
* "234"
*
*
*
* -
*
* substring("12345", 0, 3) returns "12"
*
*
*
*
* -
*
* substring("12345", 0 div 0, 3) returns ""
*
*
*
* -
*
.
* substring("12345", 1, 0 div 0) returns
*
* ""
*
*
*
* -
*
* substring("12345", -42, 1 div 0) returns
* "12345"
*
*
*
*
*
* substring("12345", -1 div 0, 1 div 0) returns
* ""
*
* @author bob mcwhirter (bob @ werken.com)
*
* @see Section 4.2 of the XPath Specification
*/
@SuppressWarnings({"rawtypes"})
public class SubstringFunction implements Function
{
/**
* Create a new SubstringFunction object.
*/
public SubstringFunction() {}
/** Returns a substring of an XPath string-value by character index.
*
* @param context the context at the point in the
* expression when the function is called
* @param args a list that contains two or three items
*
* @return a String containing the specifed character subsequence of
* the original string or the string-value of the context node
*
* @ if args has more than three
* or less than two items
*/
public Object call(Context context,
List args)
{
final int argc = args.size();
if (argc < 2 || argc > 3){
throw new RuntimeException( "substring() requires two or three arguments." );
}
final Navigator nav = context.getNavigator();
final String str = StringFunction.evaluate(args.get(0), nav );
// The spec doesn't really address this case
if (str == null) {
return "";
}
final int stringLength = (StringLengthFunction.evaluate(args.get(0), nav )).intValue();
if (stringLength == 0) {
return "";
}
Double d1 = NumberFunction.evaluate(args.get(1), nav);
if (d1.isNaN()){
return "";
}
// Round the value and subtract 1 as Java strings are zero based
int start = RoundFunction.evaluate(d1, nav).intValue() - 1;
int substringLength = stringLength;
if (argc == 3){
Double d2 = NumberFunction.evaluate(args.get(2), nav);
if (!d2.isNaN()){
substringLength = RoundFunction.evaluate(d2, nav ).intValue();
}
else {
substringLength = 0;
}
}
if (substringLength < 0) return "";
int end = start + substringLength;
if (argc == 2) end = stringLength;
// negative start is treated as 0
if ( start < 0){
start = 0;
}
else if (start > stringLength){
return "";
}
if (end > stringLength){
end = stringLength;
}
else if (end < start) return "";
if (stringLength == str.length()) {
// easy case; no surrogate pairs
return str.substring(start, end);
}
else {
return unicodeSubstring(str, start, end);
}
}
private static String unicodeSubstring(String s, int start, int end) {
StringBuffer result = new StringBuffer(s.length());
for (int jChar = 0, uChar=0; uChar < end; jChar++, uChar++) {
char c = s.charAt(jChar);
if (uChar >= start) result.append(c);
if (c >= 0xD800) { // get the low surrogate
// ???? we could check here that this is indeed a low surroagte
// we could also catch StringIndexOutOfBoundsException
jChar++;
if (uChar >= start) result.append(s.charAt(jChar));
}
}
return result.toString();
}
}