exsltdynamic.java

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/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
 * ITS 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 Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xalan.lib;

import org.w3c.dom.*;

import org.apache.xpath.objects.XObject;
import org.apache.xpath.objects.XBoolean;
import org.apache.xpath.objects.XNumber;
import org.apache.xpath.objects.XNodeSet;

import org.apache.xpath.XPath;
import org.apache.xpath.XPathContext;
import org.apache.xpath.NodeSet;
import org.apache.xpath.NodeSetDTM;

import org.xml.sax.SAXNotSupportedException;

import org.apache.xalan.extensions.ExpressionContext;
import org.apache.xalan.res.XSLMessages;
import org.apache.xalan.res.XSLTErrorResources;

import javax.xml.transform.*;
import javax.xml.parsers.*;

/**
 * <meta name="usage" content="general"/>
 * This class contains EXSLT dynamic extension functions.
 *
 * It is accessed by specifying a namespace URI as follows:
 * <pre>
 *    xmlns:math="http://exslt.org/dynamic"
 * </pre>
 * The documentation for each function has been copied from the relevant
 * EXSLT Implementer page.
 * 
 * @see <a href="http://www.exslt.org/">EXSLT</a>

 */
public class ExsltDynamic extends ExsltBase
{

   public static final String EXSL_URI = "http://exslt.org/common";
   
  /**
   * The dyn:max function calculates the maximum value for the nodes passed as 
   * the first argument, where the value of each node is calculated dynamically 
   * using an XPath expression passed as a string as the second argument. 
   * <p>
   * The expressions are evaluated relative to the nodes passed as the first argument.
   * In other words, the value for each node is calculated by evaluating the XPath 
   * expression with all context information being the same as that for the call to 
   * the dyn:max function itself, except for the following:
   * <p>
   * <ul>
   *  <li>the context node is the node whose value is being calculated.</li>
   *  <li>the context position is the position of the node within the node set passed as 
   *   the first argument to the dyn:max function, arranged in document order.</li>
   *  <li>the context size is the number of nodes passed as the first argument to the 
   *   dyn:max function.</li>
   * </ul>
   * <p>
   * The dyn:max function returns the maximum of these values, calculated in exactly 
   * the same way as for math:max. 
   * <p>
   * If the expression string passed as the second argument is an invalid XPath 
   * expression (including an empty string), this function returns NaN. 
   * <p>
   * This function must take a second argument. To calculate the maximum of a set of 
   * nodes based on their string values, you should use the math:max function.
   *
   * @param myContext The ExpressionContext passed by the extension processor
   * @param nl The node set
   * @param expr The expression string
   *
   * @return The maximum evaluation value
   */
  public static double max(ExpressionContext myContext, NodeList nl, String expr)
    throws SAXNotSupportedException
  {

    XPathContext xctxt = null;
    if (myContext instanceof XPathContext.XPathExpressionContext)
      xctxt = ((XPathContext.XPathExpressionContext) myContext).getXPathContext();
    else
      throw new SAXNotSupportedException(XSLMessages.createMessage(XSLTErrorResources.ER_INVALID_CONTEXT_PASSED, new Object[]{myContext }));

    if (expr == null || expr.length() == 0)
      return Double.NaN;
      
    NodeSetDTM contextNodes = new NodeSetDTM(nl, xctxt);
    xctxt.pushContextNodeList(contextNodes);
    
    double maxValue = Double.MIN_VALUE;
    for (int i = 0; i < contextNodes.getLength(); i++)
    {
      int contextNode = contextNodes.item(i);
      xctxt.pushCurrentNode(contextNode);
      
      double result = 0;
      try
      {
        XPath dynamicXPath = new XPath(expr, xctxt.getSAXLocator(),
                                       xctxt.getNamespaceContext(),
                                       XPath.SELECT);
        result = dynamicXPath.execute(xctxt, contextNode, xctxt.getNamespaceContext()).num();
      }
      catch (TransformerException e)
      {
        xctxt.popCurrentNode();
        xctxt.popContextNodeList();
        return Double.NaN;
      }
      
      xctxt.popCurrentNode();
              
      if (result > maxValue)
          maxValue = result;
    }      
      
    xctxt.popContextNodeList();
    return maxValue;
        
  }
  
  /**
   * The dyn:min function calculates the minimum value for the nodes passed as the 
   * first argument, where the value of each node is calculated dynamically using 
   * an XPath expression passed as a string as the second argument. 
   * <p>
   * The expressions are evaluated relative to the nodes passed as the first argument. 
   * In other words, the value for each node is calculated by evaluating the XPath 
   * expression with all context information being the same as that for the call to 
   * the dyn:min function itself, except for the following: 
   * <p>
   * <ul>
   *  <li>the context node is the node whose value is being calculated.</li>
   *  <li>the context position is the position of the node within the node set passed 
   *    as the first argument to the dyn:min function, arranged in document order.</li>
   *  <li>the context size is the number of nodes passed as the first argument to the 
   *    dyn:min function.</li>
   * </ul>
   * <p>
   * The dyn:min function returns the minimum of these values, calculated in exactly 
   * the same way as for math:min. 
   * <p>
   * If the expression string passed as the second argument is an invalid XPath expression 
   * (including an empty string), this function returns NaN. 
   * <p>
   * This function must take a second argument. To calculate the minimum of a set of 
   * nodes based on their string values, you should use the math:min function.
   *
   * @param myContext The ExpressionContext passed by the extension processor
   * @param nl The node set
   * @param expr The expression string
   *
   * @return The minimum evaluation value
   */
  public static double min(ExpressionContext myContext, NodeList nl, String expr)
    throws SAXNotSupportedException
  {
    
    XPathContext xctxt = null;
    if (myContext instanceof XPathContext.XPathExpressionContext)
      xctxt = ((XPathContext.XPathExpressionContext) myContext).getXPathContext();
    else
      throw new SAXNotSupportedException(XSLMessages.createMessage(XSLTErrorResources.ER_INVALID_CONTEXT_PASSED, new Object[]{myContext }));

    if (expr == null || expr.length() == 0)
      return Double.NaN;
      
    NodeSetDTM contextNodes = new NodeSetDTM(nl, xctxt);
    xctxt.pushContextNodeList(contextNodes);
    
    double minValue = Double.MAX_VALUE;
    for (int i = 0; i < nl.getLength(); i++)
    {
      int contextNode = contextNodes.item(i);
      xctxt.pushCurrentNode(contextNode);
      
      double result = 0;
      try
      {
        XPath dynamicXPath = new XPath(expr, xctxt.getSAXLocator(),
                                       xctxt.getNamespaceContext(),
                                       XPath.SELECT);
        result = dynamicXPath.execute(xctxt, contextNode, xctxt.getNamespaceContext()).num();
      }
      catch (TransformerException e)
      {
        xctxt.popCurrentNode();
        xctxt.popContextNodeList();
        return Double.NaN;
      }
      
      xctxt.popCurrentNode();
              
      if (result < minValue)
          minValue = result;
    }      
      
    xctxt.popContextNodeList();
    return minValue;
  
  }

  /**
   * The dyn:sum function calculates the sum for the nodes passed as the first argument, 
   * where the value of each node is calculated dynamically using an XPath expression 
   * passed as a string as the second argument. 
   * <p>
   * The expressions are evaluated relative to the nodes passed as the first argument. 
   * In other words, the value for each node is calculated by evaluating the XPath 
   * expression with all context information being the same as that for the call to 
   * the dyn:sum function itself, except for the following: 
   * <p>
   * <ul>
   *  <li>the context node is the node whose value is being calculated.</li>
   *  <li>the context position is the position of the node within the node set passed as 
   *    the first argument to the dyn:sum function, arranged in document order.</li>
   *  <li>the context size is the number of nodes passed as the first argument to the 
   *    dyn:sum function.</li>
   * </ul>
   * <p>
   * The dyn:sum function returns the sumimum of these values, calculated in exactly 
   * the same way as for sum. 
   * <p>
   * If the expression string passed as the second argument is an invalid XPath 
   * expression (including an empty string), this function returns NaN. 
   * <p>
   * This function must take a second argument. To calculate the sumimum of a set of 
   * nodes based on their string values, you should use the sum function.
   *
   * @param myContext The ExpressionContext passed by the extension processor
   * @param nl The node set
   * @param expr The expression string
   *
   * @return The sum of the evaluation value on each node
   */
  public static double sum(ExpressionContext myContext, NodeList nl, String expr)
    throws SAXNotSupportedException
  {
    XPathContext xctxt = null;
    if (myContext instanceof XPathContext.XPathExpressionContext)
      xctxt = ((XPathContext.XPathExpressionContext) myContext).getXPathContext();
    else
      throw new SAXNotSupportedException(XSLMessages.createMessage(XSLTErrorResources.ER_INVALID_CONTEXT_PASSED, new Object[]{myContext }));

    if (expr == null || expr.length() == 0)
      return Double.NaN;
      
    NodeSetDTM contextNodes = new NodeSetDTM(nl, xctxt);
    xctxt.pushContextNodeList(contextNodes);
    
    double sum = 0;
    for (int i = 0; i < nl.getLength(); i++)
    {
      int contextNode = contextNodes.item(i);
      xctxt.pushCurrentNode(contextNode);
      
      double result = 0;
      try
      {
        XPath dynamicXPath = new XPath(expr, xctxt.getSAXLocator(),
                                       xctxt.getNamespaceContext(),
                                       XPath.SELECT);
        result = dynamicXPath.execute(xctxt, contextNode, xctxt.getNamespaceContext()).num();
      }