redundentexpreliminator.java

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

  /**
   * Visit a LocationPath.
   * @param owner The owner of the expression, to which the expression can 
   *              be reset if rewriting takes place.
   * @param path The LocationPath object.
   * @return true if the sub expressions should be traversed.
   */
  public boolean visitLocationPath(ExpressionOwner owner, LocPathIterator path)
  {
  	// Don't optimize "." or single step variable paths.
  	// Both of these cases could use some further optimization by themselves.
  	if(path instanceof SelfIteratorNoPredicate)
  	{
  		return true;
  	}
  	else if(path instanceof WalkingIterator)
  	{
  		WalkingIterator wi = (WalkingIterator)path;
  		AxesWalker aw = wi.getFirstWalker();
  		if((aw instanceof FilterExprWalker) && (null == aw.getNextWalker()))
  		{
  			FilterExprWalker few = (FilterExprWalker)aw;
  			Expression exp = few.getInnerExpression();
  			if(exp instanceof Variable)
  				return true;
  		}
  	}

    if (isAbsolute(path) && (null != m_absPaths))
    {
      if(DEBUG)
        validateNewAddition(m_absPaths, owner, path);
      m_absPaths.addElement(owner);
    }
    else if (m_isSameContext && (null != m_paths))
    {
      if(DEBUG)
        validateNewAddition(m_paths, owner, path);
      m_paths.addElement(owner);
    }

    return true;
  }

  /**
   * Visit a predicate within a location path.  Note that there isn't a 
   * proper unique component for predicates, and that the expression will 
   * be called also for whatever type Expression is.
   * 
   * @param owner The owner of the expression, to which the expression can 
   *              be reset if rewriting takes place.
   * @param pred The predicate object.
   * @return true if the sub expressions should be traversed.
   */
  public boolean visitPredicate(ExpressionOwner owner, Expression pred)
  {
    boolean savedIsSame = m_isSameContext;
    m_isSameContext = false;

    // Any further down, just collect the absolute paths.
    pred.callVisitors(owner, this);

    m_isSameContext = savedIsSame;

    // We've already gone down the subtree, so don't go have the caller 
    // go any further.
    return false;
  }
  
  /**
   * Visit an XSLT top-level instruction.
   * 
   * @param elem The xsl instruction element object.
   * @return true if the sub expressions should be traversed.
   */
   boolean visitTopLevelInstruction(ElemTemplateElement elem)
   {
     int type = elem.getXSLToken();
     switch(type)
     {
       case Constants.ELEMNAME_TEMPLATE :
         return visitInstruction(elem);
       default:
         return true;
     }
   }


  /**
   * Visit an XSLT instruction.  Any element that isn't called by one 
   * of the other visit methods, will be called by this method.
   * 
   * @param elem The xsl instruction element object.
   * @return true if the sub expressions should be traversed.
   */
  boolean visitInstruction(ElemTemplateElement elem)
  {
    int type = elem.getXSLToken();
    switch (type)
    {
      case Constants.ELEMNAME_CALLTEMPLATE :
      case Constants.ELEMNAME_TEMPLATE :
      case Constants.ELEMNAME_FOREACH :
        {
          
          // Just get the select value.
          if(type == Constants.ELEMNAME_FOREACH)
          {
            ElemForEach efe = (ElemForEach) elem;
   		    
  		    Expression select = efe.getSelect();
  		    select.callVisitors(efe, this);
          }
         
  		  Vector savedPaths = m_paths;
  		  m_paths = new Vector();
  		    
  		  // Visit children.  Call the superclass callChildVisitors, because 
  		  // we don't want to visit the xsl:for-each select attribute, or, for 
  		  // that matter, the xsl:template's match attribute.
  		  elem.callChildVisitors(this, false);  		
  		  eleminateRedundentLocals(elem);
  		    
  		  m_paths = savedPaths;
 
          // select.callVisitors(efe, this);
          return false;
        }
      case Constants.ELEMNAME_NUMBER :
      case Constants.ELEMNAME_SORT :
        // Just collect absolute paths until and unless we can fully
        // analyze these cases.
        boolean savedIsSame = m_isSameContext;
        m_isSameContext = false;
        elem.callChildVisitors(this);
        m_isSameContext = savedIsSame;
        return false;
        
      default :
        return true;
    }
  }
  
  // ==== DIAGNOSTIC AND DEBUG FUNCTIONS ====
  
  /**
   * Print out to std err the number of paths reduced.
   */
  protected void diagnoseNumPaths(Vector paths, int numPathsEliminated,  
                                  int numUniquePathsEliminated) 
  {
		if (numPathsEliminated > 0)
		{ 
		  if(paths == m_paths)
		  {
		    System.err.println("Eliminated " + numPathsEliminated + " total paths!");
		    System.err.println(
		      "Consolodated " + numUniquePathsEliminated + " redundent paths!");
		  }
		  else
		  {
		    System.err.println("Eliminated " + numPathsEliminated + " total global paths!");
		    System.err.println(
		      "Consolodated " + numUniquePathsEliminated + " redundent global paths!");
		  }
		}  
  }


  /**
   * Assert that the expression is a LocPathIterator, and, if 
   * not, try to give some diagnostic info.
   */
  private final void assertIsLocPathIterator(Expression expr1, ExpressionOwner eo) 
    throws RuntimeException 
  {
		if(!(expr1 instanceof LocPathIterator))
		{
			String errMsg;
			if(expr1 instanceof Variable)
			{
				errMsg = "Programmer's assertion: expr1 not an iterator: "+
				          ((Variable)expr1).getQName();
			}
			else
			{
				errMsg = "Programmer's assertion: expr1 not an iterator: "+
				          expr1.getClass().getName();
			}
			throw new RuntimeException(errMsg + ", "+
				          eo.getClass().getName()+" "+
				          expr1.exprGetParent());
		}
  }


  /**
   * Validate some assumptions about the new LocPathIterator and it's 
   * owner and the state of the list.
   */
  private static void validateNewAddition(Vector paths, ExpressionOwner owner, 
                                          LocPathIterator path) 
		throws RuntimeException 
  {
  	assertion(owner.getExpression() == path, "owner.getExpression() != path!!!");
	int n = paths.size();
	// There should never be any duplicates in the list!
	for(int i = 0; i < n; i++)
	{
		ExpressionOwner ew = (ExpressionOwner)paths.elementAt(i);
		assertion(ew != owner, "duplicate owner on the list!!!");
		assertion(ew.getExpression() != path, "duplicate expression on the list!!!");
	}
  }
  
  /**
   * Simple assertion.
   */
  protected static void assertion(boolean b, String msg)
  {
  	if(!b)
  	{
  		throw new RuntimeException(XSLMessages.createMessage(XSLTErrorResources.ER_ASSERT_REDUNDENT_EXPR_ELIMINATOR, new Object[]{msg}));
  		// "Programmer's assertion in RundundentExprEliminator: "+msg);
  	}
  }
  
  /**
   * Since we want to sort multistep expressions by length, use 
   * a linked list with elements of type MultistepExprHolder.
   */
  class MultistepExprHolder implements Cloneable
  {
	ExpressionOwner m_exprOwner; // Will change to null once we have processed this item.
	final int m_stepCount;
	MultistepExprHolder m_next;
	
	/**
	 * Clone this object.
	 */
	public Object clone()
		throws CloneNotSupportedException
	{
		return super.clone();
	}
	
	/**
	 * Create a MultistepExprHolder.
	 * 
	 * @param exprOwner the owner of the expression we are holding.
	 *                  It must hold a LocationPathIterator.
	 * @param stepCount The number of steps in the location path.
	 */
  	MultistepExprHolder(ExpressionOwner exprOwner, int stepCount, MultistepExprHolder next)
  	{
  		m_exprOwner = exprOwner;
  		assertion(null != m_exprOwner, "exprOwner can not be null!");
  		m_stepCount = stepCount;
  		m_next = next;
  	}
	
	/**
	 * Add a new MultistepExprHolder in sorted order in the list.
	 * 
	 * @param exprOwner the owner of the expression we are holding.
	 *                  It must hold a LocationPathIterator.
	 * @param stepCount The number of steps in the location path.
	 * @return The new head of the linked list.
	 */
	MultistepExprHolder addInSortedOrder(ExpressionOwner exprOwner, int stepCount)
	{
		MultistepExprHolder first = this;
		MultistepExprHolder next = this;
		MultistepExprHolder prev = null;
		while(null != next)
		{
			if(stepCount >= next.m_stepCount)
			{
				MultistepExprHolder newholder = new MultistepExprHolder(exprOwner, stepCount, next);
				if(null == prev)
					first = newholder;
				else
					prev.m_next = newholder;
					
				return first;
			}
			prev = next;
			next = next.m_next;
		}
		
		prev.m_next = new MultistepExprHolder(exprOwner, stepCount, null);
		return first;
	}
	
	/**
	 * Remove the given element from the list.  'this' should 
	 * be the head of the list.  If the item to be removed is not 
	 * found, an assertion will be made.
	 * 
	 * @param itemToRemove The item to remove from the list.
	 * @return The head of the list, which may have changed if itemToRemove 
	 * is the same as this element.  Null if the item to remove is the 
	 * only item in the list.
	 */
	MultistepExprHolder unlink(MultistepExprHolder itemToRemove)
	{
		MultistepExprHolder first = this;
		MultistepExprHolder next = this;
		MultistepExprHolder prev = null;
		while(null != next)
		{
			if(next == itemToRemove)
			{
				if(null == prev)
					first = next.m_next;
				else
					prev.m_next = next.m_next;
				
				next.m_next = null;
					
				return first;
			}
			prev = next;
			next = next.m_next;
		}
		
		assertion(false, "unlink failed!!!");
		return null;
	}
		
	/**
	 * Get the number of linked list items.
	 */
	int getLength()
	{
		int count = 0;
		MultistepExprHolder next = this;
		while(null != next)
		{
			count++;
			next = next.m_next;
		}
		return count;
	}
	
    /**
     * Print diagnostics out for the multistep list.
     */
    protected void diagnose()
    {
      System.err.print("Found multistep iterators: " + this.getLength() + "  ");
      MultistepExprHolder next = this;
      while (null != next)
      {
        System.err.print("" + next.m_stepCount);
        next = next.m_next;
        if (null != next)
              System.err.print(", ");
      }
      System.err.println();
    }
	
  }

}