redundentexpreliminator.java

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

  			for(int j = 0; j < numStepCorrection; j++)
  			{
  				elems[i] = elems[i].getParentElem();
  			}
  		}
  	}
  	
  	// Now everyone has an equal number of ancestors.  Walk up from here 
  	// equally until all are equal.
  	ElemTemplateElement first = null;
  	while(shortestAncestorCount-- >= 0)
  	{
  		boolean areEqual = true;
  		first = elems[0];
  		for(int i = 1; i < numExprs; i++)
  		{
  			if(first != elems[i])
  			{
  				areEqual = false;
  				break;
  			}
  		}
  		// This second check is to make sure we have a common ancestor that is not the same 
  		// as the expression owner... i.e. the var decl has to go above the expression owner.
  		if(areEqual && isNotSameAsOwner(head, first) && first.canAcceptVariables())
  		{
  			if(DIAGNOSE_MULTISTEPLIST)
  			{
  				System.err.print(first.getClass().getName());
  				System.err.println(" at   " + first.getSystemId() + " Line " + first.getLineNumber());
  			}
  			return first;
  		}
   			
  		for(int i = 0; i < numExprs; i++)
  		{
  			elems[i] = elems[i].getParentElem();
  		}
  	}
  	
  	assertion(false, "Could not find common ancestor!!!");
  	return null;
  }
  
  /**
   * Find out if the given ElemTemplateElement is not the same as one of 
   * the ElemTemplateElement owners of the expressions.
   * 
   * @param head Head of linked list of expression owners.
   * @param ete The ElemTemplateElement that is a candidate for a psuedo 
   * variable parent.
   * @return true if the given ElemTemplateElement is not the same as one of 
   * the ElemTemplateElement owners of the expressions.  This is to make sure 
   * we find an ElemTemplateElement that is in a viable position to hold 
   * psuedo variables that are visible to the references.
   */
  protected boolean isNotSameAsOwner(MultistepExprHolder head, ElemTemplateElement ete)
  {
  	MultistepExprHolder next = head;
  	while(null != next)
  	{
  		ElemTemplateElement elemOwner = getElemFromExpression(next.m_exprOwner.getExpression());
  		if(elemOwner == ete)
  			return false;
  		next = next.m_next;
  	}
  	return true;
  }
  
  /**
   * Count the number of ancestors that a ElemTemplateElement has.
   * 
   * @param elem An representation of an element in an XSLT stylesheet.
   * @return The number of ancestors of elem (including the element itself).
   */
  protected int countAncestors(ElemTemplateElement elem)
  {
  	int count = 0;
  	while(null != elem)
  	{
  		count++;
  		elem = elem.getParentElem();
  	}
  	return count;
  }

  /**
   * Print out diagnostics about partial multistep evaluation.
   */
  protected void diagnoseMultistepList(
      int matchCount,
      int lengthToTest,
      boolean isGlobal)
  {
      if (matchCount > 0)
        {
        System.err.print(
          "Found multistep matches: " + matchCount + ", " + lengthToTest + " length");
        if (isGlobal)
              System.err.println(" (global)");
        else
              System.err.println();
      }
  }
  
  /**
   * Change a given number of steps to a single variable reference.
   * 
   * @param uniquePsuedoVarName The name of the variable reference.
   * @param wi The walking iterator that is to be changed.
   * @param numSteps The number of steps to be changed.
   * @param isGlobal true if this will be a global reference.
   */
  protected LocPathIterator changePartToRef(final QName uniquePsuedoVarName, WalkingIterator wi, 
                                 final int numSteps, final boolean isGlobal)
  {
  	Variable var = new Variable();
  	var.setQName(uniquePsuedoVarName);
  	var.setIsGlobal(isGlobal);
  	if(isGlobal)
  	{	ElemTemplateElement elem = getElemFromExpression(wi);
  		StylesheetRoot root = elem.getStylesheetRoot();
  		Vector vars = root.getVariablesAndParamsComposed();
  		var.setIndex(vars.size()-1);
  	}
  	
  	// Walk to the first walker after the one's we are replacing.
  	AxesWalker walker = wi.getFirstWalker();
  	for(int i = 0; i < numSteps; i++)
  	{
  		assertion(null != walker, "Walker should not be null!");
  		walker = walker.getNextWalker();
  	}
  	
  	if(null != walker)
  	{
  	
  	  FilterExprWalker few = new FilterExprWalker(wi);
  	  few.setInnerExpression(var);
  	  few.exprSetParent(wi);
  	  few.setNextWalker(walker);
  	  walker.setPrevWalker(few);
  	  wi.setFirstWalker(few);
  	  return wi;
  	}
  	else
  	{
  	  FilterExprIteratorSimple feis = new FilterExprIteratorSimple(var);
  	  feis.exprSetParent(wi.exprGetParent());
  	  return feis;
  	}
  }
  
  /**
   * Create a new WalkingIterator from the steps in another WalkingIterator.
   * 
   * @param wi The iterator from where the steps will be taken.
   * @param numSteps The number of steps from the first to copy into the new 
   *                 iterator.
   * @return The new iterator.
   */
  protected WalkingIterator createIteratorFromSteps(final WalkingIterator wi, int numSteps)
  {
  	WalkingIterator newIter = new WalkingIterator(wi.getPrefixResolver());
  	try
  	{
  		AxesWalker walker = (AxesWalker)wi.getFirstWalker().clone();
  		newIter.setFirstWalker(walker);
  		walker.setLocPathIterator(newIter);
  		for(int i = 1; i < numSteps; i++)
  		{
  			AxesWalker next = (AxesWalker)walker.getNextWalker().clone();
  			walker.setNextWalker(next);
  			next.setLocPathIterator(newIter);
  			walker = next;
  		}
  		walker.setNextWalker(null);
  	}
  	catch(CloneNotSupportedException cnse)
  	{
  		throw new WrappedRuntimeException(cnse);
  	}
  	return newIter;
  }
    
  /**
   * Compare a given number of steps between two iterators, to see if they are equal.
   * 
   * @param iter1 The first iterator to compare.
   * @param iter2 The second iterator to compare.
   * @param numSteps The number of steps to compare.
   * @return true If the given number of steps are equal.
   * 
   */
  protected boolean stepsEqual(WalkingIterator iter1, WalkingIterator iter2, 
                                         int numSteps)
  {
  	AxesWalker aw1 = iter1.getFirstWalker();
  	AxesWalker aw2 = iter2.getFirstWalker();
  	
  	for(int i = 0; (i < numSteps); i++)
  	{
  		if((null == aw1) || (null == aw2))
  		 	return false;
  		 	
  		if(!aw1.deepEquals(aw2))
  			return false;
  		
  		aw1 = aw1.getNextWalker();
  		aw2 = aw2.getNextWalker();
  	}
  	
  	assertion((null != aw1) || (null != aw2), "Total match is incorrect!");
  	
  	return true;
  }
  
  /**
   * For the reduction of location path parts, create a list of all 
   * the multistep paths with more than one step, sorted by the 
   * number of steps, with the most steps occuring earlier in the list.
   * If the list is only one member, don't bother returning it.
   * 
   * @param paths Vector of ExpressionOwner objects, which may contain null entries. 
   *              The ExpressionOwner objects must own LocPathIterator objects.
   * @return null if no multipart paths are found or the list is only of length 1, 
   * otherwise the first MultistepExprHolder in a linked list of these objects.
   */
  protected MultistepExprHolder createMultistepExprList(Vector paths)
  {
  	MultistepExprHolder first = null;
  	int n = paths.size();
  	for(int i = 0; i < n; i++)
  	{
  		ExpressionOwner eo = (ExpressionOwner)paths.elementAt(i);
  		if(null == eo)
  			continue;
  			
  		// Assuming location path iterators should be OK.
  		LocPathIterator lpi = (LocPathIterator)eo.getExpression();
  		int numPaths = countSteps(lpi);
  		if(numPaths > 1)
  		{
  			if(null == first)
  				first = new MultistepExprHolder(eo, numPaths, null);
  			else
  				first = first.addInSortedOrder(eo, numPaths);
  		}
  	}
  	
  	if((null == first) || (first.getLength() <= 1))
  		return null;
  	else
  		return first;
  }
  
  /**
   * Look through the vector from start point, looking for redundant occurances.
   * When one or more are found, create a psuedo variable declaration, insert 
   * it into the stylesheet, and replace the occurance with a reference to 
   * the psuedo variable.  When a redundent variable is found, it's slot in 
   * the vector will be replaced by null.
   * 
   * @param start The position to start looking in the vector.
   * @param targetIndex The position of firstOccuranceOwner.
   * @param firstOccuranceOwner The owner of the expression we are looking for.
   * @param psuedoVarRecipient Where to put the psuedo variables.
   * 
   * @return The number of expression occurances that were modified.
   */
  protected int findAndEliminateRedundant(int start, int firstOccuranceIndex,
                         ExpressionOwner firstOccuranceOwner, 
                         ElemTemplateElement psuedoVarRecipient,
                         Vector paths) 
                 throws org.w3c.dom.DOMException 
  {
	MultistepExprHolder head = null;
	MultistepExprHolder tail = null;
	int numPathsFound = 0;
	int n = paths.size();
	
	Expression expr1 = firstOccuranceOwner.getExpression();
	if(DEBUG)
		assertIsLocPathIterator(expr1, firstOccuranceOwner);
	boolean isGlobal = (paths == m_absPaths);
	LocPathIterator lpi = (LocPathIterator)expr1;
	int stepCount = countSteps(lpi);
	for(int j = start; j < n; j++)
	{
		ExpressionOwner owner2 = (ExpressionOwner)paths.elementAt(j);
		if(null != owner2)
		{
			Expression expr2 = owner2.getExpression();
			boolean isEqual = expr2.deepEquals(lpi);
			if(isEqual)
			{  		
				LocPathIterator lpi2  = (LocPathIterator)expr2;				
				if(null == head)
				{
					head = new MultistepExprHolder(firstOccuranceOwner, stepCount, null);
					tail = head;
					numPathsFound++;
				}
				tail.m_next = new MultistepExprHolder(owner2, stepCount, null);
				tail = tail.m_next;
	
				// 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) && isGlobal)
	{
      head = new MultistepExprHolder(firstOccuranceOwner, stepCount, null);
      numPathsFound++;
	}
	
	if(null != head)
	{
		ElemTemplateElement root = isGlobal ? psuedoVarRecipient : findCommonAncestor(head);
		LocPathIterator sharedIter = (LocPathIterator)head.m_exprOwner.getExpression();
		ElemVariable var = createPsuedoVarDecl(root, sharedIter, isGlobal);
		if(DIAGNOSE_MULTISTEPLIST)
			System.err.println("Created var: "+var.getName()+(isGlobal ? "(Global)" : ""));
		QName uniquePsuedoVarName = var.getName();
		while(null != head)
		{
			ExpressionOwner owner = head.m_exprOwner;	
			if(DIAGNOSE_MULTISTEPLIST)
				diagnoseLineNumber(owner.getExpression());
			changeToVarRef(uniquePsuedoVarName, owner, paths, root);
			head = head.m_next;
		}
		// Replace the first occurance with the variable's XPath, so  
		// that further reduction may take place if needed.
		paths.setElementAt(var.getSelect(), firstOccuranceIndex);
	}
	
	return numPathsFound;
  } 
  
  /**
   * To be removed.
   */
  protected int oldFindAndEliminateRedundant(int start, int firstOccuranceIndex,
                         ExpressionOwner firstOccuranceOwner, 
                         ElemTemplateElement psuedoVarRecipient,
                         Vector paths) 
                 throws org.w3c.dom.DOMException 
  {
	QName uniquePsuedoVarName = null;
	boolean foundFirst = false;
	int numPathsFound = 0;
	int n = paths.size();
	Expression expr1 = firstOccuranceOwner.getExpression();
	if(DEBUG)
		assertIsLocPathIterator(expr1, firstOccuranceOwner);
	boolean isGlobal = (paths == m_absPaths);
	LocPathIterator lpi = (LocPathIterator)expr1;
	for(int j = start; j < n; j++)
	{
		ExpressionOwner owner2 = (ExpressionOwner)paths.elementAt(j);
		if(null != owner2)
		{