steppattern.java

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/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
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 *
 * 1. Redistributions of source code must retain the above copyright
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 *    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.
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 * 5. Products derived from this software may not be called "Apache",
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 * 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
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package org.apache.xpath.patterns;

import java.util.Vector;

import javax.xml.transform.TransformerException;
import org.apache.xml.dtm.Axis;
import org.apache.xml.dtm.DTM;
import org.apache.xml.dtm.DTMAxisTraverser;
import org.apache.xml.dtm.DTMFilter;
import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.axes.SubContextList;
import org.apache.xpath.compiler.PsuedoNames;
import org.apache.xpath.objects.XObject;

/**
 * <meta name="usage" content="advanced"/>
 * This class represents a single pattern match step.
 */
public class StepPattern extends NodeTest implements SubContextList, ExpressionOwner
{

  /** The axis for this test. */
  protected int m_axis;

  /**
   * Construct a StepPattern that tests for namespaces and node names.
   *
   *
   * @param whatToShow Bit set defined mainly by {@link org.w3c.dom.traversal.NodeFilter}.
   * @param namespace The namespace to be tested.
   * @param name The local name to be tested.
   * @param axis The Axis for this test, one of of Axes.ANCESTORORSELF, etc.
   * @param axisForPredicate No longer used.
   */
  public StepPattern(int whatToShow, String namespace, String name, int axis,
                     int axisForPredicate)
  {

    super(whatToShow, namespace, name);

    m_axis = axis;
  }

  /**
   * Construct a StepPattern that doesn't test for node names.
   *
   *
   * @param whatToShow Bit set defined mainly by {@link org.w3c.dom.traversal.NodeFilter}.
   * @param axis The Axis for this test, one of of Axes.ANCESTORORSELF, etc.
   * @param axisForPredicate No longer used.
   */
  public StepPattern(int whatToShow, int axis, int axisForPredicate)
  {

    super(whatToShow);

    m_axis = axis;
  }

  /**
   * The target local name or psuedo name, for hash table lookup optimization.
   *  @serial
   */
  String m_targetString;  // only calculate on head

  /**
   * Calculate the local name or psuedo name of the node that this pattern will test,
   * for hash table lookup optimization.
   *
   * @see org.apache.xpath.compiler.PsuedoNames
   */
  public void calcTargetString()
  {

    int whatToShow = getWhatToShow();

    switch (whatToShow)
    {
    case DTMFilter.SHOW_COMMENT :
      m_targetString = PsuedoNames.PSEUDONAME_COMMENT;
      break;
    case DTMFilter.SHOW_TEXT :
    case DTMFilter.SHOW_CDATA_SECTION :
    case (DTMFilter.SHOW_TEXT | DTMFilter.SHOW_CDATA_SECTION) :
      m_targetString = PsuedoNames.PSEUDONAME_TEXT;
      break;
    case DTMFilter.SHOW_ALL :
      m_targetString = PsuedoNames.PSEUDONAME_ANY;
      break;
    case DTMFilter.SHOW_DOCUMENT :
    case DTMFilter.SHOW_DOCUMENT | DTMFilter.SHOW_DOCUMENT_FRAGMENT :
      m_targetString = PsuedoNames.PSEUDONAME_ROOT;
      break;
    case DTMFilter.SHOW_ELEMENT :
      if (this.WILD == m_name)
        m_targetString = PsuedoNames.PSEUDONAME_ANY;
      else
        m_targetString = m_name;
      break;
    default :
      m_targetString = PsuedoNames.PSEUDONAME_ANY;
      break;
    }
  }

  /**
   * Get the local name or psuedo name of the node that this pattern will test,
   * for hash table lookup optimization.
   *
   *
   * @return local name or psuedo name of the node.
   * @see org.apache.xpath.compiler.PsuedoNames
   */
  public String getTargetString()
  {
    return m_targetString;
  }

  /**
   * Reference to nodetest and predicate for
   * parent or ancestor.
   * @serial
   */
  StepPattern m_relativePathPattern;

  /**
   * This function is used to fixup variables from QNames to stack frame
   * indexes at stylesheet build time.
   * @param vars List of QNames that correspond to variables.  This list
   * should be searched backwards for the first qualified name that
   * corresponds to the variable reference qname.  The position of the
   * QName in the vector from the start of the vector will be its position
   * in the stack frame (but variables above the globalsTop value will need
   * to be offset to the current stack frame).
   * @param globalsSize The number of variables in the global variable area.
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize)
  {

    super.fixupVariables(vars, globalsSize);

    if (null != m_predicates)
    {
      for (int i = 0; i < m_predicates.length; i++)
      {
        m_predicates[i].fixupVariables(vars, globalsSize);
      }
    }

    if (null != m_relativePathPattern)
    {
      m_relativePathPattern.fixupVariables(vars, globalsSize);
    }
  }

  /**
   * Set the reference to nodetest and predicate for
   * parent or ancestor.
   *
   *
   * @param expr The relative pattern expression.
   */
  public void setRelativePathPattern(StepPattern expr)
  {

    m_relativePathPattern = expr;
    expr.exprSetParent(this);

    calcScore();
  }

  /**
   * Get the reference to nodetest and predicate for
   * parent or ancestor.
   *
   *
   * @return The relative pattern expression.
   */
  public StepPattern getRelativePathPattern()
  {
    return m_relativePathPattern;
  }

  //  /**
  //   * Set the list of predicate expressions for this pattern step.
  //   * @param predicates List of expression objects.
  //   */
  //  public void setPredicates(Expression[] predicates)
  //  {
  //    m_predicates = predicates;
  //  }

  /**
   * Set the list of predicate expressions for this pattern step.
   * @return List of expression objects.
   */
  public Expression[] getPredicates()
  {
    return m_predicates;
  }

  /**
   * The list of predicate expressions for this pattern step.
   *  @serial
   */
  Expression[] m_predicates;

  /**
   * Tell if this expression or it's subexpressions can traverse outside
   * the current subtree.
   *
   * NOTE: Ancestors tests with predicates are problematic, and will require
   * special treatment.
   *
   * @return true if traversal outside the context node's subtree can occur.
   */
  public boolean canTraverseOutsideSubtree()
  {

    int n = getPredicateCount();

    for (int i = 0; i < n; i++)
    {
      if (getPredicate(i).canTraverseOutsideSubtree())
        return true;
    }

    return false;
  }

  /**
   * Get a predicate expression.
   *
   *
   * @param i The index of the predicate.
   *
   * @return A predicate expression.
   */
  public Expression getPredicate(int i)
  {
    return m_predicates[i];
  }

  /**
   * Get the number of predicates for this match pattern step.
   *
   *
   * @return the number of predicates for this match pattern step.
   */
  public final int getPredicateCount()
  {
    return (null == m_predicates) ? 0 : m_predicates.length;
  }

  /**
   * Set the predicates for this match pattern step.
   *
   *
   * @param predicates An array of expressions that define predicates
   *                   for this step.
   */
  public void setPredicates(Expression[] predicates)
  {

    m_predicates = predicates;
    if(null != predicates)
    {
    	for(int i = 0; i < predicates.length; i++)
    	{
    		predicates[i].exprSetParent(this);
    	}
    }

    calcScore();
  }

  /**
   * Static calc of match score.
   */
  public void calcScore()
  {

    if ((getPredicateCount() > 0) || (null != m_relativePathPattern))
    {
      m_score = SCORE_OTHER;
    }
    else
      super.calcScore();

    if (null == m_targetString)
      calcTargetString();
  }

  /**
   * Execute this pattern step, including predicates.
   *
   *
   * @param xctxt XPath runtime context.
   * @param currentNode The current node context.
   *
   * @return {@link org.apache.xpath.patterns.NodeTest#SCORE_NODETEST},
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_NONE},
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_NSWILD},
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_QNAME}, or
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_OTHER}.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt, int currentNode)
          throws javax.xml.transform.TransformerException
  {

    DTM dtm = xctxt.getDTM(currentNode);

    if (dtm != null)
    {
      int expType = dtm.getExpandedTypeID(currentNode);

      return execute(xctxt, currentNode, dtm, expType);
    }

    return NodeTest.SCORE_NONE;
  }

  /**
   * Execute this pattern step, including predicates.
   *
   *
   * @param xctxt XPath runtime context.
   *
   * @return {@link org.apache.xpath.patterns.NodeTest#SCORE_NODETEST},
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_NONE},
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_NSWILD},
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_QNAME}, or
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_OTHER}.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt)
          throws javax.xml.transform.TransformerException
  {
    return execute(xctxt, xctxt.getCurrentNode());
  }

  /**
   * Execute an expression in the XPath runtime context, and return the
   * result of the expression.
   *
   *
   * @param xctxt The XPath runtime context.
   * @param currentNode The currentNode.
   * @param dtm The DTM of the current node.
   * @param expType The expanded type ID of the current node.
   *
   * @return The result of the expression in the form of a <code>XObject</code>.
   *
   * @throws javax.xml.transform.TransformerException if a runtime exception
   *         occurs.
   */
  public XObject execute(
          XPathContext xctxt, int currentNode, DTM dtm, int expType)
            throws javax.xml.transform.TransformerException
  {

    if (m_whatToShow == NodeTest.SHOW_BYFUNCTION)
    {
      if (null != m_relativePathPattern)
      {
        return m_relativePathPattern.execute(xctxt);
      }
      else
        return NodeTest.SCORE_NONE;
    }

    XObject score;

    score = super.execute(xctxt, currentNode, dtm, expType);

    if (score == NodeTest.SCORE_NONE)
      return NodeTest.SCORE_NONE;

    if (getPredicateCount() != 0)
    {
      if (!executePredicates(xctxt, dtm, currentNode))
        return NodeTest.SCORE_NONE;
    }

    if (null != m_relativePathPattern)
      return m_relativePathPattern.executeRelativePathPattern(xctxt, dtm,
              currentNode);

    return score;
  }

  /**
   * New Method to check whether the current node satisfies a position predicate
   *
   * @param xctxt The XPath runtime context.
   * @param predPos Which predicate we're evaluating of foo[1][2][3].
   * @param dtm The DTM of the current node.
   * @param context The currentNode.
   * @param pos The position being requested, i.e. the value returned by 
   *            m_predicates[predPos].execute(xctxt).
   *
   * @return true of the position of the context matches pos, false otherwise.
   */
  private final boolean checkProximityPosition(XPathContext xctxt,
          int predPos, DTM dtm, int context, int pos)
  {

    try
    {
      DTMAxisTraverser traverser =
        dtm.getAxisTraverser(Axis.PRECEDINGSIBLING);

      for (int child = traverser.first(context); DTM.NULL != child;
              child = traverser.next(context, child))
      {
        try
        {
          xctxt.pushCurrentNode(child);

          if (NodeTest.SCORE_NONE != super.execute(xctxt, child))
          {
            boolean pass = true;

            try
            {
              xctxt.pushSubContextList(this);

              for (int i = 0; i < predPos; i++)
              {
                xctxt.pushPredicatePos(i);
                try
                {
                  XObject pred = m_predicates[i].execute(xctxt);
                  
                  try
                  {
                    if (XObject.CLASS_NUMBER == pred.getType())
                    {
                      throw new Error("Why: Should never have been called");
                    }
                    else if (!pred.boolWithSideEffects())
                    {
                      pass = false;
    
                      break;
                    }
                  }
                  finally
                  {
                    pred.detach();
                  }
                }
                finally
                {
                  xctxt.popPredicatePos();
                }
              }
            }
            finally
            {
              xctxt.popSubContextList();
            }

            if (pass)
              pos--;

            if (pos < 1)
              return false;
          }
        }
        finally
        {
          xctxt.popCurrentNode();
        }
      }
    }
    catch (javax.xml.transform.TransformerException se)
    {

      // TODO: should keep throw sax exception...
      throw new java.lang.RuntimeException(se.getMessage());
    }

    return (pos == 1);