redundentexpreliminator.java

来自「java jdk 1.4的源码」· Java 代码 · 共 1,474 行 · 第 1/4 页

			Expression expr2 = owner2.getExpression();
			boolean isEqual = expr2.deepEquals(lpi);
			if(isEqual)
			{  		
				LocPathIterator lpi2  = (LocPathIterator)expr2;				
				if(!foundFirst)
				{
					foundFirst = true;
					// Insert variable decl into psuedoVarRecipient
					// We want to insert this into the first legitimate 
					// position for a variable.
				    ElemVariable var = createPsuedoVarDecl(psuedoVarRecipient, lpi, isGlobal);
				    if(null == var)
				    	return 0;
				    uniquePsuedoVarName = var.getName();
	
					changeToVarRef(uniquePsuedoVarName, firstOccuranceOwner, 
					               paths, psuedoVarRecipient);
					               
					// Replace the first occurance with the variable's XPath, so  
					// that further reduction may take place if needed.
					paths.setElementAt(var.getSelect(), firstOccuranceIndex);
					numPathsFound++;
				}
	
				changeToVarRef(uniquePsuedoVarName, owner2, paths, psuedoVarRecipient);
	
				// Null out the occurance, so we don't have to test it again.
				paths.setElementAt(null, j);
				
				// foundFirst = true;
				numPathsFound++;
			}
		}
	}
	
	// Change all globals in xsl:templates, etc, to global vars no matter what.
	if((0 == numPathsFound) && (paths == m_absPaths))
	{
      ElemVariable var = createPsuedoVarDecl(psuedoVarRecipient, lpi, true);
      if(null == var)
        return 0;
	  uniquePsuedoVarName = var.getName();
      changeToVarRef(uniquePsuedoVarName, firstOccuranceOwner, paths, psuedoVarRecipient);
      paths.setElementAt(var.getSelect(), firstOccuranceIndex);
      numPathsFound++;
	}
	return numPathsFound;
  }
  
  /**
   * Count the steps in a given location path.
   * 
   * @param lpi The location path iterator that owns the steps.
   * @return The number of steps in the given location path.
   */
  protected int countSteps(LocPathIterator lpi)
  {
  	if(lpi instanceof WalkingIterator)
  	{
  		WalkingIterator wi = (WalkingIterator)lpi;
  		AxesWalker aw = wi.getFirstWalker();
  		int count = 0;
  		while(null != aw)
  		{
  			count++;
  			aw = aw.getNextWalker();
  		}
  		return count;
  	}
  	else
  		return 1;
  }
  
  /**
   * Change the expression owned by the owner argument to a variable reference 
   * of the given name.
   * 
   * Warning: For global vars, this function relies on the variable declaration 
   * to which it refers having been added just prior to this function being called,
   * so that the reference index can be determined from the size of the global variables 
   * list minus one.
   * 
   * @param varName The name of the variable which will be referenced.
   * @param owner The owner of the expression which will be replaced by a variable ref.
   * @param paths The paths list that the iterator came from, mainly to determine
   *              if this is a local or global reduction.
   * @param psuedoVarRecipient The element within whose scope the variable is 
   *                           being inserted, possibly a StylesheetRoot.
   */
  protected void changeToVarRef(QName varName, ExpressionOwner owner, 
                                Vector paths, ElemTemplateElement psuedoVarRecipient) 
  {
	Variable varRef = (paths == m_absPaths) ? new VariableSafeAbsRef() : new Variable();
	varRef.setQName(varName);
	if(paths == m_absPaths)
	{
		StylesheetRoot root = (StylesheetRoot)psuedoVarRecipient;
		Vector globalVars = root.getVariablesAndParamsComposed();
		// Assume this operation is occuring just after the decl has 
		// been added.
		varRef.setIndex(globalVars.size()-1);
		varRef.setIsGlobal(true);
	}
	owner.setExpression(varRef);
  }

  /**
   * Create a psuedo variable reference that will represent the 
   * shared redundent XPath, and add it to the stylesheet.
   * 
   * @param psuedoVarRecipient The broadest scope of where the variable 
   * should be inserted, usually an xsl:template or xsl:for-each.
   * @param lpi The LocationPathIterator that the variable should represent.
   * @param isGlobal true if the paths are global.
   * @return The new psuedo var element.
   */
  protected ElemVariable createPsuedoVarDecl(
      ElemTemplateElement psuedoVarRecipient,
      LocPathIterator lpi, boolean isGlobal)
      throws org.w3c.dom.DOMException
  {
    QName uniquePsuedoVarName = new QName (PSUEDOVARNAMESPACE, "#"+m_uniquePsuedoVarID);
    m_uniquePsuedoVarID++;
  		
  	if(isGlobal)
  	{
  	  return createGlobalPsuedoVarDecl(uniquePsuedoVarName, 
  	                                  (StylesheetRoot)psuedoVarRecipient, lpi);
  	}
  	else						
      return createLocalPsuedoVarDecl(uniquePsuedoVarName, psuedoVarRecipient, lpi);
  }
  
  /**
   * Create a psuedo variable reference that will represent the 
   * shared redundent XPath, for a local reduction.
   * 
   * @param uniquePsuedoVarName The name of the new variable.
   * @param stylesheetRoot The broadest scope of where the variable 
   *        should be inserted, which must be a StylesheetRoot element in this case.
   * @param lpi The LocationPathIterator that the variable should represent.
   * @return null if the decl was not created, otherwise the new Psuedo var  
   *              element.
   */
  protected ElemVariable createGlobalPsuedoVarDecl(QName uniquePsuedoVarName,
                                           StylesheetRoot stylesheetRoot, 
                                           LocPathIterator lpi) 
        throws org.w3c.dom.DOMException 
  {
  	ElemVariable psuedoVar = new ElemVariable();
  	psuedoVar.setIsTopLevel(true);
	XPath xpath = new XPath(lpi);
	psuedoVar.setSelect(xpath);
	psuedoVar.setName(uniquePsuedoVarName);
	
	Vector globalVars = stylesheetRoot.getVariablesAndParamsComposed();
	psuedoVar.setIndex(globalVars.size());
	globalVars.addElement(psuedoVar);
	return psuedoVar;
  }

  
  

  /**
   * Create a psuedo variable reference that will represent the 
   * shared redundent XPath, for a local reduction.
   * 
   * @param uniquePsuedoVarName The name of the new variable.
   * @param psuedoVarRecipient The broadest scope of where the variable 
   * should be inserted, usually an xsl:template or xsl:for-each.
   * @param lpi The LocationPathIterator that the variable should represent.
   * @param addToContext true if the decl should be added to psuedoVarRecipient.
   * @return null if the decl was not created, otherwise the new Psuedo var  
   *              element.
   */
  protected ElemVariable createLocalPsuedoVarDecl(QName uniquePsuedoVarName,
                                           ElemTemplateElement psuedoVarRecipient, 
                                           LocPathIterator lpi) 
        throws org.w3c.dom.DOMException 
  {
		ElemVariable psuedoVar = new ElemVariablePsuedo();
		
		XPath xpath = new XPath(lpi);
		psuedoVar.setSelect(xpath);
		psuedoVar.setName(uniquePsuedoVarName);

		ElemVariable var = addVarDeclToElem(psuedoVarRecipient, lpi, psuedoVar);
		
		lpi.exprSetParent(var);
		
		return var;
  }

  /**
   * Add the given variable to the psuedoVarRecipient.
   */
  protected ElemVariable addVarDeclToElem(
    ElemTemplateElement psuedoVarRecipient,
    LocPathIterator lpi,
    ElemVariable psuedoVar)
    throws org.w3c.dom.DOMException
  {
    // Create psuedo variable element
    ElemTemplateElement ete = psuedoVarRecipient.getFirstChildElem();

    lpi.callVisitors(null, m_varNameCollector);

    // If the location path contains variables, we have to insert the 
    // psuedo variable after the reference. (Otherwise, we want to 
    // insert it as close as possible to the top, so we'll be sure 
    // it is in scope for any other vars.
    if (m_varNameCollector.getVarCount() > 0)
    {
      ElemTemplateElement baseElem = getElemFromExpression(lpi);
      ElemVariable varElem = getPrevVariableElem(baseElem);
      while (null != varElem)
      {
        if (m_varNameCollector.doesOccur(varElem.getName()))
          {
          psuedoVarRecipient = varElem.getParentElem();
          ete = varElem.getNextSiblingElem();
          break;
        }
        varElem = getPrevVariableElem(varElem);
      }
    }

    if ((null != ete) && (Constants.ELEMNAME_PARAMVARIABLE == ete.getXSLToken()))
    {
      // Can't stick something in front of a param, so abandon! (see variable13.xsl)
      if(isParam(lpi))
        return null;

      while (null != ete)
      {
        ete = ete.getNextSiblingElem();
        if ((null != ete) && Constants.ELEMNAME_PARAMVARIABLE != ete.getXSLToken())
            break;
      }
    }
    psuedoVarRecipient.insertBefore(psuedoVar, ete);
    m_varNameCollector.reset();
    return psuedoVar;
  }
    
  /**
   * Tell if the expr param is contained within an xsl:param.
   */
  protected boolean isParam(ExpressionNode expr)
  {
  	while(null != expr)
  	{
  		if(expr instanceof ElemTemplateElement)
  			break;
  		expr = expr.exprGetParent();
  	}
  	if(null != expr)
  	{
  		ElemTemplateElement ete = (ElemTemplateElement)expr;
  		while(null != ete)
  		{
  			int type = ete.getXSLToken();
  			switch(type)
  			{
  				case Constants.ELEMNAME_PARAMVARIABLE:
  					return true;
  				case Constants.ELEMNAME_TEMPLATE:
  				case Constants.ELEMNAME_STYLESHEET:
  					return false;
  			}
  			ete = ete.getParentElem();
  		}
  	}
  	return false;
  	
  }
  
  /**
   * Find the previous occurance of a xsl:variable.  Stop 
   * the search when a xsl:for-each, xsl:template, or xsl:stylesheet is 
   * encountered.
   * 
   * @param elem Should be non-null template element.
   * @return The first previous occurance of an xsl:variable or xsl:param, 
   * or null if none is found.
   */
  protected ElemVariable getPrevVariableElem(ElemTemplateElement elem)
  {
  	// This could be somewhat optimized.  since getPreviousSiblingElem is a  
  	// fairly expensive operation.
  	while(null != (elem = getPrevElementWithinContext(elem)))
  	{
  		int type = elem.getXSLToken();
  			
  		if((Constants.ELEMNAME_VARIABLE == type) ||
  		   (Constants.ELEMNAME_PARAMVARIABLE == type))
  		{
  			return (ElemVariable)elem;
  		}
  	}
  	return null;
  }
  
  /**
   * Get the previous sibling or parent of the given template, stopping at 
   * xsl:for-each, xsl:template, or xsl:stylesheet.
   * 
   * @param elem Should be non-null template element.
   * @return previous sibling or parent, or null if previous is xsl:for-each, 
   * xsl:template, or xsl:stylesheet.
   */
  protected ElemTemplateElement getPrevElementWithinContext(ElemTemplateElement elem)
  {
  	ElemTemplateElement prev = elem.getPreviousSiblingElem();
  	if(null == prev)
  		prev = elem.getParentElem();
  	if(null != prev)
  	{
  	  int type = prev.getXSLToken();
  	  if((Constants.ELEMNAME_FOREACH == type) || 
  	     (Constants.ELEMNAME_TEMPLATE == type) ||
  	     (Constants.ELEMNAME_STYLESHEET == type))
  	  {
  	  	prev = null;
  	  }
  	}
  	return prev;
  }
  
  /**
   * From an XPath expression component, get the ElemTemplateElement 
   * owner.
   * 
   * @param expr Should be static expression with proper parentage.
   * @return Valid ElemTemplateElement, or throw a runtime exception 
   * if it is not found.
   */
  protected ElemTemplateElement getElemFromExpression(Expression expr)
  {
  	ExpressionNode parent = expr.exprGetParent();
  	while(null != parent)
  	{
  		if(parent instanceof ElemTemplateElement)
  			return (ElemTemplateElement)parent;
  		parent = parent.exprGetParent();
  	}
  	throw new RuntimeException(XSLMessages.createMessage(XSLTErrorResources.ER_ASSERT_NO_TEMPLATE_PARENT, null));
  	// "Programmer's error! expr has no ElemTemplateElement parent!");
  }
      
  /**
   * Tell if the given LocPathIterator is relative to an absolute path, i.e. 
   * in not dependent on the context.
   * 
   * @return true if the LocPathIterator is not dependent on the context node.
   */
  public boolean isAbsolute(LocPathIterator path)
  {
  	int analysis = path.getAnalysisBits();
    boolean isAbs = (WalkerFactory.isSet(analysis, WalkerFactory.BIT_ROOT) || 
           WalkerFactory.isSet(analysis, WalkerFactory.BIT_ANY_DESCENDANT_FROM_ROOT));
    if(isAbs)
    {
    	isAbs = m_absPathChecker.checkAbsolute(path);
    }
    return isAbs;
  }