http://xml.apache.org/xalan-j/: Serializer to write out XML, HTML etc. as a stream of characters from an input DOM or from input SAX events. (The Apache Software Foundation) 
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 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: WalkingIterator.java 469314 2006-10-30 23:31:59Z minchau $
 */
package org.apache.xpath.axes;

import org.apache.xml.dtm.DTM;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.VariableStack;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.compiler.Compiler;
import org.apache.xpath.compiler.OpMap;


Location path iterator that uses Walkers.

/**
 * Location path iterator that uses Walkers.
 */

public class WalkingIterator extends LocPathIterator implements ExpressionOwner
{
    static final long serialVersionUID = 9110225941815665906L;
  
Create a WalkingIterator iterator, including creation
of step walkers from the opcode list, and call back
into the Compiler to create predicate expressions.

Params:
  • compiler – The Compiler which is creating
this expression.
  • opPos – The position of this iterator in the
opcode list from the compiler.
  • shouldLoadWalkers – True if walkers should be
loaded, or false if this is a derived iterator and
it doesn't wish to load child walkers.
Throws:
/**
   * Create a WalkingIterator iterator, including creation
   * of step walkers 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.
   * @param shouldLoadWalkers True if walkers should be
   * loaded, or false if this is a derived iterator and
   * it doesn't wish to load child walkers.
   *
   * @throws javax.xml.transform.TransformerException
   */
  WalkingIterator(
          Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers)
            throws javax.xml.transform.TransformerException
  {
    super(compiler, opPos, analysis, shouldLoadWalkers);
    
    int firstStepPos = OpMap.getFirstChildPos(opPos);

    if (shouldLoadWalkers)
    {
      m_firstWalker = WalkerFactory.loadWalkers(this, compiler, firstStepPos, 0);
      m_lastUsedWalker = m_firstWalker;
    }
  }
  
  
Create a WalkingIterator object.

Params:
  • nscontext – The namespace context for this iterator,
should be OK if null.
/**
   * Create a WalkingIterator object.
   *
   * @param nscontext The namespace context for this iterator,
   * should be OK if null.
   */
  public WalkingIterator(PrefixResolver nscontext)
  {

    super(nscontext);
  }
  
  
  
Get the analysis bits for this walker, as defined in the WalkerFactory.

Returns:One of WalkerFactory#BIT_DESCENDANT, etc.
/** 
   * Get the analysis bits for this walker, as defined in the WalkerFactory.
   * @return One of WalkerFactory#BIT_DESCENDANT, etc.
   */
  public int getAnalysisBits()
  {
    int bits = 0;
    if (null != m_firstWalker)
    {    	
      AxesWalker walker = m_firstWalker;

      while (null != walker)
      {
        int bit = walker.getAnalysisBits();
        bits |= bit;
        walker = walker.getNextWalker();
      }       
    }
    return bits;
  }
  
  
Get a cloned WalkingIterator that holds the same
position as this iterator.

Throws:
Returns:A clone of this iterator that holds the same node position.
/**
   * Get a cloned WalkingIterator that holds the same
   * position as this iterator.
   *
   * @return A clone of this iterator that holds the same node position.
   *
   * @throws CloneNotSupportedException
   */
  public Object clone() throws CloneNotSupportedException
  {

    WalkingIterator clone = (WalkingIterator) super.clone();

    //    clone.m_varStackPos = this.m_varStackPos;
    //    clone.m_varStackContext = this.m_varStackContext;
    if (null != m_firstWalker)
    {
      clone.m_firstWalker = m_firstWalker.cloneDeep(clone, null);
    }

    return clone;
  }
  
  
Reset the iterator.

/**
   * Reset the iterator.
   */
  public void reset()
  {

    super.reset();

    if (null != m_firstWalker)
    {
      m_lastUsedWalker = m_firstWalker;

      m_firstWalker.setRoot(m_context);
    }

  }
  
  
Initialize the context values for this expression
after it is cloned.

Params:
  • context – The XPath runtime context for this
transformation.
/**
   * Initialize the context values for this expression
   * after it is cloned.
   *
   * @param context The XPath runtime context for this
   * transformation.
   */
  public void setRoot(int context, Object environment)
  {

    super.setRoot(context, environment);
    
    if(null != m_firstWalker)
    {
      m_firstWalker.setRoot(context);
      m_lastUsedWalker = m_firstWalker;
    }
  }
  
  
 Returns the next node in the set and advances the position of the
iterator in the set. After a NodeIterator is created, the first call
to nextNode() returns the first node in the set.

Returns: The next Node in the set being iterated over, or
  null if there are no more members in that set.
/**
   *  Returns the next node in the set and advances the position of the
   * iterator in the set. After a NodeIterator is created, the first call
   * to nextNode() returns the first node in the set.
   * @return  The next <code>Node</code> in the set being iterated over, or
   *   <code>null</code> if there are no more members in that set.
   */
  public int nextNode()
  {
  	if(m_foundLast)
  		return DTM.NULL;

    // If the variable stack position is not -1, we'll have to 
    // set our position in the variable stack, so our variable access 
    // will be correct.  Iterators that are at the top level of the 
    // expression need to reset the variable stack, while iterators 
    // in predicates do not need to, and should not, since their execution
    // may be much later than top-level iterators.  
    // m_varStackPos is set in setRoot, which is called 
    // from the execute method.
    if (-1 == m_stackFrame)
    {
      return returnNextNode(m_firstWalker.nextNode());
    }
    else
    {
      VariableStack vars = m_execContext.getVarStack();

      // These three statements need to be combined into one operation.
      int savedStart = vars.getStackFrame();

      vars.setStackFrame(m_stackFrame);

      int n = returnNextNode(m_firstWalker.nextNode());

      // These two statements need to be combined into one operation.
      vars.setStackFrame(savedStart);

      return n;
    }
  }

  
  
Get the head of the walker list.

Returns:The head of the walker list, or null
if this iterator does not implement walkers.
@xsl.usageadvanced
/**
   * Get the head of the walker list.
   *
   * @return The head of the walker list, or null
   * if this iterator does not implement walkers.
   * @xsl.usage advanced
   */
  public final AxesWalker getFirstWalker()
  {
    return m_firstWalker;
  }
  
  
Set the head of the walker list.

Params:
  • walker – Should be a valid AxesWalker.
@xsl.usageadvanced
/**
   * Set the head of the walker list.
   * 
   * @param walker Should be a valid AxesWalker.
   * @xsl.usage advanced
   */
  public final void setFirstWalker(AxesWalker walker)
  {
    m_firstWalker = walker;
  }


  
Set the last used walker.

Params:
  • walker – The last used walker, or null.
@xsl.usageadvanced
/**
   * Set the last used walker.
   *
   * @param walker The last used walker, or null.
   * @xsl.usage advanced
   */
  public final void setLastUsedWalker(AxesWalker walker)
  {
    m_lastUsedWalker = walker;
  }

  
Get the last used walker.

Returns:The last used walker, or null.
@xsl.usageadvanced
/**
   * Get the last used walker.
   *
   * @return The last used walker, or null.
   * @xsl.usage advanced
   */
  public final AxesWalker getLastUsedWalker()
  {
    return m_lastUsedWalker;
  }
  
  
 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.

/**
   *  Detaches the iterator from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state. After<code>detach</code> has been invoked, calls to
   * <code>nextNode</code> or<code>previousNode</code> will raise the
   * exception INVALID_STATE_ERR.
   */
  public void detach()
  {   
    if(m_allowDetach)
    {
	  	AxesWalker walker = m_firstWalker; 
	    while (null != walker)
	    {
	      walker.detach();
	      walker = walker.getNextWalker();
	    }
	
	    m_lastUsedWalker = null;
	    
	    // Always call the superclass detach last!
	    super.detach();
    }
  }
  
  
This function is used to fixup variables from QNames to stack frame 
indexes at stylesheet build time.

Params:
  • 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).
/**
   * 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).
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize)
  {
    m_predicateIndex = -1;

    AxesWalker walker = m_firstWalker;

    while (null != walker)
    {
      walker.fixupVariables(vars, globalsSize);
      walker = walker.getNextWalker();
    }
  }
  
  
See Also:
  • callVisitors.callVisitors(ExpressionOwner, XPathVisitor)
/**
   * @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
   */
  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
  {
  	 	if(visitor.visitLocationPath(owner, this))
  	 	{
  	 		if(null != m_firstWalker)
  	 		{
  	 			m_firstWalker.callVisitors(this, visitor);
  	 		}
  	 	}
  }

  
  
The last used step walker in the walker list.
 @serial 
/** The last used step walker in the walker list.
   *  @serial */
  protected AxesWalker m_lastUsedWalker;

  
The head of the step walker list.
 @serial 
/** The head of the step walker list.
   *  @serial */
  protected AxesWalker m_firstWalker;

  
See Also:
  • getExpression.getExpression()
/**
   * @see ExpressionOwner#getExpression()
   */
  public Expression getExpression()
  {
    return m_firstWalker;
  }

  
See Also:
  • setExpression.setExpression(Expression)
/**
   * @see ExpressionOwner#setExpression(Expression)
   */
  public void setExpression(Expression exp)
  {
  	exp.exprSetParent(this);
  	m_firstWalker = (AxesWalker)exp;
  }
  
    
See Also:
  • deepEquals.deepEquals(Expression)
/**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr)
    {
      if (!super.deepEquals(expr))
                return false;

      AxesWalker walker1 = m_firstWalker;
      AxesWalker walker2 = ((WalkingIterator)expr).m_firstWalker;
      while ((null != walker1) && (null != walker2))
      {
        if(!walker1.deepEquals(walker2))
        	return false;
        walker1 = walker1.getNextWalker();
        walker2 = walker2.getNextWalker();
      }
      
      if((null != walker1) || (null != walker2))
      	return false;

      return true;
    }

}