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UnionPathIterator.javaAPI DocJava SE 5 API15659Fri Aug 26 14:56:06 BST 2005com.sun.org.apache.xpath.internal.axes

UnionPathIterator

public class UnionPathIterator extends LocPathIterator implements PathComponent, Cloneable, DTMIterator, Serializable
This class extends NodeSetDTM, which implements DTMIterator, and fetches nodes one at a time in document order based on a XPath UnionExpr. As each node is iterated via nextNode(), the node is also stored in the NodeVector, so that previousNode() can easily be done.
xsl.usage
advanced

Fields Summary
protected LocPathIterator[]
m_exprs
The location path iterators, one for each location path contained in the union expression.
protected DTMIterator[]
m_iterators
The location path iterators, one for each location path contained in the union expression.
Constructors Summary
public UnionPathIterator()
Constructor to create an instance which you can add location paths to.


    super();

    // m_mutable = false;
    // m_cacheNodes = false;
    m_iterators = null;
    m_exprs = null;
public UnionPathIterator(Compiler compiler, int opPos)
Create a UnionPathIterator object, including creation of location path iterators from the opcode list, and call back into the Compiler to create predicate expressions.

param
compiler The Compiler which is creating this expression.
param
opPos The position of this iterator in the opcode list from the compiler.
throws
javax.xml.transform.TransformerException


    super();

    opPos = compiler.getFirstChildPos(opPos);

    loadLocationPaths(compiler, opPos, 0);
Methods Summary
public voidaddIterator(com.sun.org.apache.xml.internal.dtm.DTMIterator expr)
Add an iterator to the union list.

param
iter non-null reference to a location path iterator.


    // Increase array size by only 1 at a time.  Fix this
    // if it looks to be a problem.
    if (null == m_iterators)
    {
      m_iterators = new DTMIterator[1];
      m_iterators[0] = expr;
    }
    else
    {
      DTMIterator[] exprs = m_iterators;
      int len = m_iterators.length;

      m_iterators = new DTMIterator[len + 1];

      System.arraycopy(exprs, 0, m_iterators, 0, len);

      m_iterators[len] = expr;
    }
    expr.nextNode();
    if(expr instanceof Expression)
    	((Expression)expr).exprSetParent(this);
public voidcallVisitors(com.sun.org.apache.xpath.internal.ExpressionOwner owner, com.sun.org.apache.xpath.internal.XPathVisitor visitor)

see
com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)

  	 	if(visitor.visitUnionPath(owner, this))
  	 	{
  	 		if(null != m_exprs)
  	 		{
  	 			int n = m_exprs.length;
  	 			for(int i = 0; i < n; i++)
  	 			{
  	 				m_exprs[i].callVisitors(new iterOwner(i), visitor);
  	 			}
  	 		}
  	 	}
public java.lang.Objectclone()
Get a cloned LocPathIterator that holds the same position as this iterator.

return
A clone of this iterator that holds the same node position.
throws
CloneNotSupportedException


    UnionPathIterator clone = (UnionPathIterator) super.clone();
//    if (m_iterators != null)
//    {
//      int n = m_iterators.length;
//
//      clone.m_iterators = new LocPathIterator[n];
//
//      for (int i = 0; i < n; i++)
//      {
//        clone.m_iterators[i] = (LocPathIterator)m_iterators[i].clone();
//      }
//    }

    return clone;
protected com.sun.org.apache.xpath.internal.axes.LocPathIteratorcreateDTMIterator(com.sun.org.apache.xpath.internal.compiler.Compiler compiler, int opPos)
Create a new location path iterator.

param
compiler The Compiler which is creating this expression.
param
opPos The position of this iterator in the
return
New location path iterator.
throws
javax.xml.transform.TransformerException

    LocPathIterator lpi = (LocPathIterator)WalkerFactory.newDTMIterator(compiler, opPos, 
                                      (compiler.getLocationPathDepth() <= 0));
    return lpi;
public static com.sun.org.apache.xpath.internal.axes.LocPathIteratorcreateUnionIterator(com.sun.org.apache.xpath.internal.compiler.Compiler compiler, int opPos)
This will return an iterator capable of handling the union of paths given.

param
compiler The Compiler which is creating this expression.
param
opPos The position of this iterator in the opcode list from the compiler.
return
Object that is derived from LocPathIterator.
throws
javax.xml.transform.TransformerException

  	// For the moment, I'm going to first create a full UnionPathIterator, and 
  	// then see if I can reduce it to a UnionChildIterator.  It would obviously 
  	// be more effecient to just test for the conditions for a UnionChildIterator, 
  	// and then create that directly.
  	UnionPathIterator upi = new UnionPathIterator(compiler, opPos);
  	int nPaths = upi.m_exprs.length;
  	boolean isAllChildIterators = true;
  	for(int i = 0; i < nPaths; i++)
  	{
  		LocPathIterator lpi = upi.m_exprs[i];
  		
  		if(lpi.getAxis() != Axis.CHILD)
  		{
  			isAllChildIterators = false;
  			break;
  		}
  		else
  		{
  			// check for positional predicates or position function, which won't work.
  			if(HasPositionalPredChecker.check(lpi))
  			{
  				isAllChildIterators = false;
  				break;
  			}
  		}
  	}
  	if(isAllChildIterators)
  	{
  		UnionChildIterator uci = new UnionChildIterator();
  		
	  	for(int i = 0; i < nPaths; i++)
	  	{
	  		PredicatedNodeTest lpi = upi.m_exprs[i];
	  		// I could strip the lpi down to a pure PredicatedNodeTest, but 
	  		// I don't think it's worth it.  Note that the test can be used 
	  		// as a static object... so it doesn't have to be cloned.
	  		uci.addNodeTest(lpi);
	  	}
	  	return uci;
  		
  	}
  	else
  		return upi;
public booleandeepEquals(com.sun.org.apache.xpath.internal.Expression expr)

see
Expression#deepEquals(Expression)

      if (!super.deepEquals(expr))
            return false;

      UnionPathIterator upi = (UnionPathIterator) expr;

      if (null != m_exprs)
      {
        int n = m_exprs.length;
        
        if((null == upi.m_exprs) || (upi.m_exprs.length != n))
        	return false;
        
        for (int i = 0; i < n; i++)
        {
          if(!m_exprs[i].deepEquals(upi.m_exprs[i]))
          	return false;
        }
      }
      else if (null != upi.m_exprs)
      {
          return false;
      }

      return true;
public voiddetach()
Detaches the iterator from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state. Afterdetach has been invoked, calls to nextNode orpreviousNode will raise the exception INVALID_STATE_ERR.

          if(m_allowDetach && null != m_iterators){         
                  int n = m_iterators.length;
                  for(int i = 0; i < n; i++)
                  {
                          m_iterators[i].detach();
                  }
                  m_iterators = null;                                
          }
public voidfixupVariables(java.util.Vector vars, int globalsSize)
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).

    for (int i = 0; i < m_exprs.length; i++) 
    {
      m_exprs[i].fixupVariables(vars, globalsSize);
    }
public intgetAnalysisBits()
Get the analysis bits for this walker, as defined in the WalkerFactory.

return
One of WalkerFactory#BIT_DESCENDANT, etc.

    int bits = 0;
    
    if (m_exprs != null)
    {
      int n = m_exprs.length;

      for (int i = 0; i < n; i++)
      {
      	int bit = m_exprs[i].getAnalysisBits();
        bits |= bit;
      }
    }

    return bits;
public intgetAxis()
Returns the axis being iterated, if it is known.

return
Axis.CHILD, etc., or -1 if the axis is not known or is of multiple types.

    // Could be smarter.
    return -1;
protected voidloadLocationPaths(com.sun.org.apache.xpath.internal.compiler.Compiler compiler, int opPos, int count)
Initialize the location path iterators. Recursive.

param
compiler The Compiler which is creating this expression.
param
opPos The position of this iterator in the opcode list from the compiler.
param
count The insert position of the iterator.
throws
javax.xml.transform.TransformerException


    // TODO: Handle unwrapped FilterExpr
    int steptype = compiler.getOp(opPos);

    if (steptype == OpCodes.OP_LOCATIONPATH)
    {
      loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

      m_exprs[count] = createDTMIterator(compiler, opPos);
      m_exprs[count].exprSetParent(this);
    }
    else
    {

      // Have to check for unwrapped functions, which the LocPathIterator
      // doesn't handle. 
      switch (steptype)
      {
      case OpCodes.OP_VARIABLE :
      case OpCodes.OP_EXTFUNCTION :
      case OpCodes.OP_FUNCTION :
      case OpCodes.OP_GROUP :
        loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

        WalkingIterator iter =
          new WalkingIterator(compiler.getNamespaceContext());
        iter.exprSetParent(this);
          
        if(compiler.getLocationPathDepth() <= 0)
          iter.setIsTopLevel(true);

        iter.m_firstWalker = new com.sun.org.apache.xpath.internal.axes.FilterExprWalker(iter);

        iter.m_firstWalker.init(compiler, opPos, steptype);

        m_exprs[count] = iter;
        break;
      default :
        m_exprs = new LocPathIterator[count];
      }
    }
public intnextNode()
Returns the next node in the set and advances the position of the iterator in the set. After a DTMIterator is created, the first call to nextNode() returns the first node in the set.

return
The next Node in the set being iterated over, or null if there are no more members in that set.

  	if(m_foundLast)
  		return DTM.NULL;

    // Loop through the iterators getting the current fetched 
    // node, and get the earliest occuring in document order
    int earliestNode = DTM.NULL;

    if (null != m_iterators)
    {
      int n = m_iterators.length;
      int iteratorUsed = -1;

      for (int i = 0; i < n; i++)
      {
        int node = m_iterators[i].getCurrentNode();

        if (DTM.NULL == node)
          continue;
        else if (DTM.NULL == earliestNode)
        {
          iteratorUsed = i;
          earliestNode = node;
        }
        else
        {
          if (node == earliestNode)
          {

            // Found a duplicate, so skip past it.
            m_iterators[i].nextNode();
          }
          else
          {
            DTM dtm = getDTM(node);

            if (dtm.isNodeAfter(node, earliestNode))
            {
              iteratorUsed = i;
              earliestNode = node;
            }
          }
        }
      }

      if (DTM.NULL != earliestNode)
      {
        m_iterators[iteratorUsed].nextNode();

        incrementCurrentPos();
      }
      else
        m_foundLast = true;
    }

    m_lastFetched = earliestNode;

    return earliestNode;
private voidreadObject(java.io.ObjectInputStream stream)
Read the object from a serialization stream.

param
stream Input stream to read from
throws
java.io.IOException
throws
javax.xml.transform.TransformerException

    try
    {
      stream.defaultReadObject();
      m_clones =  new IteratorPool(this);
    }
    catch (ClassNotFoundException cnfe)
    {
      throw new javax.xml.transform.TransformerException(cnfe);
    }
public voidsetRoot(int context, java.lang.Object environment)
Initialize the context values for this expression after it is cloned.

param
execContext The XPath runtime context for this transformation.

    super.setRoot(context, environment);

    try
    {
      if (null != m_exprs)
      {
        int n = m_exprs.length;
        DTMIterator newIters[] = new DTMIterator[n];
  
        for (int i = 0; i < n; i++)
        {
          DTMIterator iter = m_exprs[i].asIterator(m_execContext, context);
          newIters[i] = iter;
          iter.nextNode();
        }
        m_iterators = newIters;
      }
    }
    catch(Exception e)
    {
      throw new com.sun.org.apache.xml.internal.utils.WrappedRuntimeException(e);
    }