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/*
 * $Header: /cvs/jaxen/jaxen/src/java/main/org/jaxen/function/SubstringFunction.java,v 1.16 2006/02/05 21:47:41 elharo Exp $
 * $Revision: 1.16 $
 * $Date: 2006/02/05 21:47:41 $
 *
 * ====================================================================
 *
 * 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 .
 *
 */
package org.navimatrix.jaxen.function;

import java.util.List;

import org.navimatrix.jaxen.Context;
import org.navimatrix.jaxen.Function;
import org.navimatrix.jaxen.FunctionCallException;
import org.navimatrix.jaxen.Navigator;
/**
 * 

* 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 */ 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 * * @throws FunctionCallException if args has more than three * or less than two items */ public Object call(Context context, List args) throws FunctionCallException { final int argc = args.size(); if (argc < 2 || argc > 3){ throw new FunctionCallException( "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(); } }




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