src/org/apache/xalan/lib/ExsltSets.java

/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999-2003 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 apache@apache.org.
 *
 * 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
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 * 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
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 * 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.Node;
import org.w3c.dom.NodeList;
import org.apache.xpath.NodeSet;
import org.apache.xml.utils.DOMHelper;
import java.util.Hashtable;
import javax.xml.parsers.*;

/**
 * <meta name="usage" content="general"/>
 * This class contains EXSLT set extension functions.
 * It is accessed by specifying a namespace URI as follows:
 * <pre>
 *    xmlns:set="http://exslt.org/sets"
 * </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 ExsltSets extends ExsltBase
{   
  /**
   * The set:leading function returns the nodes in the node set passed as the first argument that
   * precede, in document order, the first node in the node set passed as the second argument. If
   * the first node in the second node set is not contained in the first node set, then an empty
   * node set is returned. If the second node set is empty, then the first node set is returned.
   * 
   * @param nl1 NodeList for first node-set.
   * @param nl2 NodeList for second node-set.
   * @return a NodeList containing the nodes in nl1 that precede in document order the first
   * node in nl2; an empty node-set if the first node in nl2 is not in nl1; all of nl1 if nl2
   * is empty.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
   */
  public static NodeList leading (NodeList nl1, NodeList nl2)
  {
    if (nl2.getLength() == 0)
      return nl1;
      
    NodeSet ns1 = new NodeSet(nl1);
    NodeSet leadNodes = new NodeSet();
    Node endNode = nl2.item(0);
    if (!ns1.contains(endNode))
      return leadNodes; // empty NodeSet
      
    for (int i = 0; i < nl1.getLength(); i++)
    {
      Node testNode = nl1.item(i);
      if (DOMHelper.isNodeAfter(testNode, endNode) 
          && !DOMHelper.isNodeTheSame(testNode, endNode))
        leadNodes.addElement(testNode);
    }
    return leadNodes;
  }
  
  /**
   * The set:trailing function returns the nodes in the node set passed as the first argument that 
   * follow, in document order, the first node in the node set passed as the second argument. If 
   * the first node in the second node set is not contained in the first node set, then an empty 
   * node set is returned. If the second node set is empty, then the first node set is returned. 
   * 
   * @param nl1 NodeList for first node-set.
   * @param nl2 NodeList for second node-set.
   * @return a NodeList containing the nodes in nl1 that follow in document order the first
   * node in nl2; an empty node-set if the first node in nl2 is not in nl1; all of nl1 if nl2
   * is empty.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
   */
  public static NodeList trailing (NodeList nl1, NodeList nl2)
  {
    if (nl2.getLength() == 0)
      return nl1;
      
    NodeSet ns1 = new NodeSet(nl1);
    NodeSet trailNodes = new NodeSet();
    Node startNode = nl2.item(0);
    if (!ns1.contains(startNode))
      return trailNodes; // empty NodeSet
      
    for (int i = 0; i < nl1.getLength(); i++)
    {
      Node testNode = nl1.item(i);
      if (DOMHelper.isNodeAfter(startNode, testNode) 
          && !DOMHelper.isNodeTheSame(startNode, testNode))
        trailNodes.addElement(testNode);          
    }
    return trailNodes;
  }
  
  /**
   * The set:intersection function returns a node set comprising the nodes that are within 
   * both the node sets passed as arguments to it.
   * 
   * @param nl1 NodeList for first node-set.
   * @param nl2 NodeList for second node-set.
   * @return a NodeList containing the nodes in nl1 that are also
   * in nl2.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
   */
  public static NodeList intersection(NodeList nl1, NodeList nl2)
  {
    NodeSet ns1 = new NodeSet(nl1);
    NodeSet ns2 = new NodeSet(nl2);
    NodeSet inter = new NodeSet();

    inter.setShouldCacheNodes(true);

    for (int i = 0; i < ns1.getLength(); i++)
    {
      Node n = ns1.elementAt(i);

      if (ns2.contains(n))
        inter.addElement(n);
    }

    return inter;
  }
  
  /**
   * The set:difference function returns the difference between two node sets - those nodes that 
   * are in the node set passed as the first argument that are not in the node set passed as the 
   * second argument.
   * 
   * @param nl1 NodeList for first node-set.
   * @param nl2 NodeList for second node-set.
   * @return a NodeList containing the nodes in nl1 that are not in nl2.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
   */
  public static NodeList difference(NodeList nl1, NodeList nl2)
  {
    NodeSet ns1 = new NodeSet(nl1);
    NodeSet ns2 = new NodeSet(nl2);

    NodeSet diff = new NodeSet();

    diff.setShouldCacheNodes(true);

    for (int i = 0; i < ns1.getLength(); i++)
    {
      Node n = ns1.elementAt(i);

      if (!ns2.contains(n))
        diff.addElement(n);
    }

    return diff;
  }
  
  /**
   * The set:distinct function returns a subset of the nodes contained in the node-set NS passed 
   * as the first argument. Specifically, it selects a node N if there is no node in NS that has 
   * the same string value as N, and that precedes N in document order. 
   * 
   * @param nl NodeList for the node-set.
   * @return a NodeList with nodes from nl containing distinct string values.
   * In other words, if more than one node in nl contains the same string value,
   * only include the first such node found.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
   */
  public static NodeList distinct(NodeList nl)
  {
    NodeSet dist = new NodeSet();
    dist.setShouldCacheNodes(true);

    Hashtable stringTable = new Hashtable();
    
    for (int i = 0; i < nl.getLength(); i++)
    {
      Node currNode = nl.item(i);
      String key = toString(currNode);
      
      if (key == null)
        dist.addElement(currNode);
      else if (!stringTable.containsKey(key))
      {
        stringTable.put(key, currNode);
        dist.addElement(currNode);      	
      }
    }

    return dist;
  }
  
  /**
   * The set:has-same-node function returns true if the node set passed as the first argument shares 
   * any nodes with the node set passed as the second argument. If there are no nodes that are in both
   * node sets, then it returns false. 
   * 
   * The Xalan extensions MethodResolver converts 'has-same-node' to 'hasSameNode'.
   * 
   * Note: Not to be confused with hasSameNodes in the Xalan namespace, which returns true if
   * the two node sets contain the exactly the same nodes (perhaps in a different order), 
   * otherwise false.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
   */
  public static boolean hasSameNode(NodeList nl1, NodeList nl2)
  {
    
    NodeSet ns1 = new NodeSet(nl1);
    NodeSet ns2 = new NodeSet(nl2);

    for (int i = 0; i < ns1.getLength(); i++)
    {
      if (ns2.contains(ns1.elementAt(i)))
        return true;
    }
    return false;
  }
  
}