/*
* $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/StringLengthFunction.java,v 1.12 2006/02/05 21:47:41 elharo Exp $
* $Revision: 1.12 $
* $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 <bob@werken.com> and
* James Strachan <jstrachan@apache.org>. For more information on the
* Jaxen Project, please see <http://www.jaxen.org/>.
*
* $Id: StringLengthFunction.java,v 1.12 2006/02/05 21:47:41 elharo Exp $
*/
package org.orbeon.jaxen.function;
import org.orbeon.jaxen.Context;
import org.orbeon.jaxen.Function;
import org.orbeon.jaxen.FunctionCallException;
import org.orbeon.jaxen.Navigator;
import java.util.List;
/**
* <p><b>4.2</b> <code><i>number</i> string-length(<i>string</i>)</code></p>
*
* <p>
* The <b>string-length</b> function returns the number of <strong>Unicode characters</strong>
* in its argument. This is <strong>not</strong> necessarily
* the same as the number <strong>Java chars</strong>
* in the corresponding Java string. In particular, if the Java <code>String</code>
* contains surrogate pairs each such pair will be counted as only one character
* by this function. If the argument is omitted,
* it returns the length of the string-value of the context node.
* </p>
*
* @author bob mcwhirter (bob @ werken.com)
* @see <a href="http://www.w3.org/TR/xpath#function-string-length" target="_top">Section
* 4.2 of the XPath Specification</a>
*/
public class StringLengthFunction implements Function
{
/**
* Create a new <code>StringLengthFunction</code> object.
*/
public StringLengthFunction() {}
/**
* <p>
* Returns the number of Unicode characters in the string-value of the argument.
* </p>
*
* @param context the context at the point in the
* expression when the function is called
* @param args a list containing the item whose string-value is to be counted.
* If empty, the length of the context node's string-value is returned.
*
* @return a <code>Double</code> giving the number of Unicode characters
*
* @throws FunctionCallException if args has more than one item
*/
public Object call(Context context,
List args) throws FunctionCallException
{
if (args.size() == 0)
{
return evaluate( context.getNodeSet(),
context.getNavigator() );
}
else if (args.size() == 1)
{
return evaluate( args.get(0),
context.getNavigator() );
}
throw new FunctionCallException( "string-length() requires one argument." );
}
/**
* <p>
* Returns the number of Unicode characters in the string-value of
* an object.
* </p>
*
* @param obj the object whose string-value is counted
* @param nav used to calculate the string-values of the first two arguments
*
* @return a <code>Double</code> giving the number of Unicode characters
*
* @throws FunctionCallException if the string contains mismatched surrogates
*/
public static Double evaluate(Object obj, Navigator nav) throws FunctionCallException
{
String str = StringFunction.evaluate( obj, nav );
// String.length() counts UTF-16 code points; not Unicode characters
char[] data = str.toCharArray();
int length = 0;
for (int i = 0; i < data.length; i++) {
char c = data[i];
length++;
// if this is a high surrogate; assume the next character is
// is a low surrogate and skip it
if (c >= 0xD800) {
try {
char low = data[i+1];
if (low < 0xDC00 || low > 0xDFFF) {
throw new FunctionCallException("Bad surrogate pair in string " + str);
}
i++; // increment past low surrogate
}
catch (ArrayIndexOutOfBoundsException ex) {
throw new FunctionCallException("Bad surrogate pair in string " + str);
}
}
}
return new Double(length);
}
}