import com.sun.org.apache.xpath.internal.VariableStack; //导入依赖的package包/类
/**
 *  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;
  }
}
 

import com.sun.org.apache.xpath.internal.VariableStack; //导入依赖的package包/类
/**
 * Execute the expression.  Meant for reuse by other FilterExpr iterators
 * that are not derived from this object.
 */
public static XNodeSet executeFilterExpr(int context, XPathContext xctxt,
                                                                                              PrefixResolver prefixResolver,
                                                                                              boolean isTopLevel,
                                                                                              int stackFrame,
                                                                                              Expression expr )
  throws com.sun.org.apache.xml.internal.utils.WrappedRuntimeException
{
  PrefixResolver savedResolver = xctxt.getNamespaceContext();
  XNodeSet result = null;

  try
  {
    xctxt.pushCurrentNode(context);
    xctxt.setNamespaceContext(prefixResolver);

    // The setRoot operation can take place with a reset operation,
    // and so we may not be in the context of LocPathIterator#nextNode,
    // so we have to set up the variable context, execute the expression,
    // and then restore the variable context.

    if (isTopLevel)
    {
      // System.out.println("calling m_expr.execute(getXPathContext())");
      VariableStack vars = xctxt.getVarStack();

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

      result = (com.sun.org.apache.xpath.internal.objects.XNodeSet) expr.execute(xctxt);
      result.setShouldCacheNodes(true);

      // These two statements need to be combined into one operation.
      vars.setStackFrame(savedStart);
    }
    else
        result = (com.sun.org.apache.xpath.internal.objects.XNodeSet) expr.execute(xctxt);

  }
  catch (javax.xml.transform.TransformerException se)
  {

    // TODO: Fix...
    throw new com.sun.org.apache.xml.internal.utils.WrappedRuntimeException(se);
  }
  finally
  {
    xctxt.popCurrentNode();
    xctxt.setNamespaceContext(savedResolver);
  }
  return result;
}