LocPathIterator


1   /*
2    * Copyright 1999-2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  /*
17   * $Id: LocPathIterator.java,v 1.41 2004/02/17 04:32:08 minchau Exp $
18   */
19  package org.apache.xpath.axes;
20  
21  import org.apache.xalan.res.XSLMessages;
22  import org.apache.xml.dtm.DTM;
23  import org.apache.xml.dtm.DTMFilter;
24  import org.apache.xml.dtm.DTMIterator;
25  import org.apache.xml.dtm.DTMManager;
26  import org.apache.xml.utils.PrefixResolver;
27  import org.apache.xpath.ExpressionOwner;
28  import org.apache.xpath.XPathContext;
29  import org.apache.xpath.XPathVisitor;
30  import org.apache.xpath.compiler.Compiler;
31  import org.apache.xpath.objects.XNodeSet;
32  import org.apache.xpath.objects.XObject;
33  import org.apache.xpath.res.XPATHErrorResources;
34  
35  /**
36   * This class extends NodeSetDTM, which implements NodeIterator,
37   * and fetches nodes one at a time in document order based on a XPath
38   * <a HREF="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a>.
39   *
40   * <p>If setShouldCacheNodes(true) is called,
41   * as each node is iterated via nextNode(), the node is also stored
42   * in the NodeVector, so that previousNode() can easily be done, except in
43   * the case where the LocPathIterator is "owned" by a UnionPathIterator,
44   * in which case the UnionPathIterator will cache the nodes.</p>
45   * @xsl.usage advanced
46   */
47  public abstract class LocPathIterator extends PredicatedNodeTest
48          implements Cloneable  , DTMIterator, java.io.Serializable  , PathComponent
49  {
50      
51    /**
52     * Create a LocPathIterator object.
53     *
54     * @param nscontext The namespace context for this iterator,
55     * should be OK if null.
56     */
57    protected LocPathIterator()
58    {
59    }
60  
61  
62    /**
63     * Create a LocPathIterator object.
64     *
65     * @param nscontext The namespace context for this iterator,
66     * should be OK if null.
67     */
68    protected LocPathIterator(PrefixResolver nscontext)
69    {
70  
71      setLocPathIterator(this);
72      m_prefixResolver = nscontext;
73    }
74  
75    /**
76     * Create a LocPathIterator object, including creation
77     * of step walkers from the opcode list, and call back
78     * into the Compiler to create predicate expressions.
79     *
80     * @param compiler The Compiler which is creating
81     * this expression.
82     * @param opPos The position of this iterator in the
83     * opcode list from the compiler.
84     *
85     * @throws javax.xml.transform.TransformerException
86     */
87    protected LocPathIterator(Compiler   compiler, int opPos, int analysis)
88            throws javax.xml.transform.TransformerException  
89    {
90      this(compiler, opPos, analysis, true);
91    }
92  
93    /**
94     * Create a LocPathIterator object, including creation
95     * of step walkers from the opcode list, and call back
96     * into the Compiler to create predicate expressions.
97     *
98     * @param compiler The Compiler which is creating
99     * this expression.
100    * @param opPos The position of this iterator in the
101    * opcode list from the compiler.
102    * @param shouldLoadWalkers True if walkers should be
103    * loaded, or false if this is a derived iterator and
104    * it doesn't wish to load child walkers.
105    *
106    * @throws javax.xml.transform.TransformerException
107    */
108   protected LocPathIterator(
109           Compiler   compiler, int opPos, int analysis, boolean shouldLoadWalkers)
110             throws javax.xml.transform.TransformerException  
111   {
112     setLocPathIterator(this);
113   }
114   
115   /** 
116    * Get the analysis bits for this walker, as defined in the WalkerFactory.
117    * @return One of WalkerFactory#BIT_DESCENDANT, etc.
118    */
119   public int getAnalysisBits()
120   {
121     int axis = getAxis();
122     int bit = WalkerFactory.getAnalysisBitFromAxes(axis);
123     return bit;
124   }
125   
126   /**
127    * Read the object from a serialization stream.
128    *
129    * @param stream Input stream to read from
130    *
131    * @throws java.io.IOException
132    * @throws javax.xml.transform.TransformerException
133    */
134   private void readObject(java.io.ObjectInputStream   stream)
135           throws java.io.IOException  , javax.xml.transform.TransformerException  
136   {
137     try
138     {
139       stream.defaultReadObject();
140       m_clones =  new IteratorPool(this);
141     }
142     catch (ClassNotFoundException   cnfe)
143     {
144       throw new javax.xml.transform.TransformerException  (cnfe);
145     }
146   }
147   
148   /**
149    * Set the environment in which this iterator operates, which should provide:
150    * a node (the context node... same value as "root" defined below) 
151    * a pair of non-zero positive integers (the context position and the context size) 
152    * a set of variable bindings 
153    * a function library 
154    * the set of namespace declarations in scope for the expression.
155    * 
156    * <p>At this time the exact implementation of this environment is application 
157    * dependent.  Probably a proper interface will be created fairly soon.</p>
158    * 
159    * @param environment The environment object.
160    */
161   public void setEnvironment(Object   environment)
162   {
163     // no-op for now.
164   }
165   
166   /**
167    * Get an instance of a DTM that "owns" a node handle.  Since a node 
168    * iterator may be passed without a DTMManager, this allows the 
169    * caller to easily get the DTM using just the iterator.
170    *
171    * @param nodeHandle the nodeHandle.
172    *
173    * @return a non-null DTM reference.
174    */
175   public DTM getDTM(int nodeHandle)
176   {
177     // %OPT%
178     return m_execContext.getDTM(nodeHandle);
179   }
180   
181   /**
182    * Get an instance of the DTMManager.  Since a node 
183    * iterator may be passed without a DTMManager, this allows the 
184    * caller to easily get the DTMManager using just the iterator.
185    *
186    * @return a non-null DTMManager reference.
187    */
188   public DTMManager getDTMManager()
189   {
190     return m_execContext.getDTMManager();
191   }
192   
193   /**
194    * Execute this iterator, meaning create a clone that can
195    * store state, and initialize it for fast execution from
196    * the current runtime state.  When this is called, no actual
197    * query from the current context node is performed.
198    *
199    * @param xctxt The XPath execution context.
200    *
201    * @return An XNodeSet reference that holds this iterator.
202    *
203    * @throws javax.xml.transform.TransformerException
204    */
205   public XObject execute(XPathContext xctxt)
206           throws javax.xml.transform.TransformerException  
207   {
208 
209     XNodeSet iter = new XNodeSet((LocPathIterator)m_clones.getInstance());
210 
211     iter.setRoot(xctxt.getCurrentNode(), xctxt);
212 
213     return iter;
214   }
215     
216   /**
217    * Execute an expression in the XPath runtime context, and return the
218    * result of the expression.
219    *
220    *
221    * @param xctxt The XPath runtime context.
222    * @param handler The target content handler.
223    *
224    * @return The result of the expression in the form of a <code>XObject</code>.
225    *
226    * @throws javax.xml.transform.TransformerException if a runtime exception
227    *         occurs.
228    * @throws org.xml.sax.SAXException
229    */
230   public void executeCharsToContentHandler(
231           XPathContext xctxt, org.xml.sax.ContentHandler   handler)
232             throws javax.xml.transform.TransformerException  ,
233                    org.xml.sax.SAXException  
234   {
235     LocPathIterator clone = (LocPathIterator)m_clones.getInstance();
236 
237     int current = xctxt.getCurrentNode();
238     clone.setRoot(current, xctxt);
239     
240     int node = clone.nextNode();
241     DTM dtm = clone.getDTM(node);
242     clone.detach();
243     
244     if(node != DTM.NULL)
245     {
246       dtm.dispatchCharactersEvents(node, handler, false);
247     }
248   }
249   
250   /**
251    * Given an select expression and a context, evaluate the XPath
252    * and return the resulting iterator.
253    * 
254    * @param xctxt The execution context.
255    * @param contextNode The node that "." expresses.
256    * @param namespaceContext The context in which namespaces in the
257    * XPath are supposed to be expanded.
258    * 
259    * @throws TransformerException thrown if the active ProblemListener decides
260    * the error condition is severe enough to halt processing.
261    *
262    * @throws javax.xml.transform.TransformerException
263    * @xsl.usage experimental
264    */
265   public DTMIterator asIterator(
266           XPathContext xctxt, int contextNode)
267             throws javax.xml.transform.TransformerException  
268   {
269     XNodeSet iter = new XNodeSet((LocPathIterator)m_clones.getInstance());
270 
271     iter.setRoot(contextNode, xctxt);
272 
273     return iter;
274   }
275 
276   
277   /**
278    * Tell if the expression is a nodeset expression.
279    * 
280    * @return true if the expression can be represented as a nodeset.
281    */
282   public boolean isNodesetExpr()
283   {
284     return true;
285   }
286   
287   /**
288    * Return the first node out of the nodeset, if this expression is 
289    * a nodeset expression.  This is the default implementation for 
290    * nodesets.  Derived classes should try and override this and return a 
291    * value without having to do a clone operation.
292    * @param xctxt The XPath runtime context.
293    * @return the first node out of the nodeset, or DTM.NULL.
294    */
295   public int asNode(XPathContext xctxt)
296     throws javax.xml.transform.TransformerException  
297   {
298     DTMIterator iter = (DTMIterator)m_clones.getInstance();
299     
300     int current = xctxt.getCurrentNode();
301     
302     iter.setRoot(current, xctxt);
303 
304     int next = iter.nextNode();
305     // m_clones.freeInstance(iter);
306     iter.detach();
307     return next;
308   }
309   
310   /**
311    * Evaluate this operation directly to a boolean.
312    *
313    * @param xctxt The runtime execution context.
314    *
315    * @return The result of the operation as a boolean.
316    *
317    * @throws javax.xml.transform.TransformerException
318    */
319   public boolean bool(XPathContext xctxt)
320           throws javax.xml.transform.TransformerException  
321   {
322     return (asNode(xctxt) != DTM.NULL);
323   }
324 
325 
326   /**
327    * Set if this is an iterator at the upper level of
328    * the XPath.
329    *
330    * @param b true if this location path is at the top level of the
331    *          expression.
332    * @xsl.usage advanced
333    */
334   public void setIsTopLevel(boolean b)
335   {
336     m_isTopLevel = b;
337   }
338 
339   /**
340    * Get if this is an iterator at the upper level of
341    * the XPath.
342    *
343    * @return true if this location path is at the top level of the
344    *          expression.
345    * @xsl.usage advanced
346    */
347   public boolean getIsTopLevel()
348   {
349     return m_isTopLevel;
350   }
351   
352   /**
353    * Initialize the context values for this expression
354    * after it is cloned.
355    *
356    * @param execContext The XPath runtime context for this
357    * transformation.
358    */
359   public void setRoot(int context, Object   environment)
360   {
361 
362     m_context = context;
363     
364     XPathContext xctxt = (XPathContext)environment;
365     m_execContext = xctxt;
366     m_cdtm = xctxt.getDTM(context);
367     
368     m_currentContextNode = context; // only if top level?
369     
370     // Yech, shouldn't have to do this.  -sb
371     if(null == m_prefixResolver)
372         m_prefixResolver = xctxt.getNamespaceContext();
373         
374     m_lastFetched = DTM.NULL;
375     m_foundLast = false;
376     m_pos = 0;
377     m_length = -1;
378 
379     if (m_isTopLevel)
380       this.m_stackFrame = xctxt.getVarStack().getStackFrame();
381       
382     // reset();
383   }
384 
385   /**
386    * Set the next position index of this iterator.
387    *
388    * @param next A value greater than or equal to zero that indicates the next
389    * node position to fetch.
390    */
391   protected void setNextPosition(int next)
392   {
393     assertion(false, "setNextPosition not supported in this iterator!");
394   }
395 
396   /**
397    * Get the current position, which is one less than
398    * the next nextNode() call will retrieve.  i.e. if
399    * you call getCurrentPos() and the return is 0, the next
400    * fetch will take place at index 1.
401    *
402    * @return A value greater than or equal to zero that indicates the next
403    * node position to fetch.
404    */
405   public final int getCurrentPos()
406   {
407     return m_pos;
408   }
409 
410 
411   /**
412    * If setShouldCacheNodes(true) is called, then nodes will
413    * be cached.  They are not cached by default.
414    *
415    * @param b True if this iterator should cache nodes.
416    */
417   public void setShouldCacheNodes(boolean b)
418   {
419 
420     assertion(false, "setShouldCacheNodes not supported by this iterater!");
421   }
422   
423   /**
424    * Tells if this iterator can have nodes added to it or set via 
425    * the <code>setItem(int node, int index)</code> method.
426    * 
427    * @return True if the nodelist can be mutated.
428    */
429   public boolean isMutable()
430   {
431     return false;
432   }
433 
434   /**
435    * Set the current position in the node set.
436    *
437    * @param i Must be a valid index greater
438    * than or equal to zero and less than m_cachedNodes.size().
439    */
440   public void setCurrentPos(int i)
441   {
442     assertion(false, "setCurrentPos not supported by this iterator!");
443   }
444   
445   /**
446    * Increment the current position in the node set.
447    */
448   public void incrementCurrentPos()
449   {
450     m_pos++;
451   }
452 
453 
454   /**
455    * Get the length of the cached nodes.
456    *
457    * <p>Note: for the moment at least, this only returns
458    * the size of the nodes that have been fetched to date,
459    * it doesn't attempt to run to the end to make sure we
460    * have found everything.  This should be reviewed.</p>
461    *
462    * @return The size of the current cache list.
463    */
464   public int size()
465   {
466     assertion(false, "size() not supported by this iterator!");
467     return 0;
468   }
469 
470   /**
471    *  Returns the <code>index</code> th item in the collection. If
472    * <code>index</code> is greater than or equal to the number of nodes in
473    * the list, this returns <code>null</code> .
474    * @param index  Index into the collection.
475    * @return  The node at the <code>index</code> th position in the
476    *   <code>NodeList</code> , or <code>null</code> if that is not a valid
477    *   index.
478    */
479   public int item(int index)
480   {
481     assertion(false, "item(int index) not supported by this iterator!");
482     return 0;
483   }
484   
485   /**
486    * Sets the node at the specified index of this vector to be the
487    * specified node. The previous component at that position is discarded.
488    *
489    * <p>The index must be a value greater than or equal to 0 and less
490    * than the current size of the vector.  
491    * The iterator must be in cached mode.</p>
492    * 
493    * <p>Meant to be used for sorted iterators.</p>
494    *
495    * @param node Node to set
496    * @param index Index of where to set the node
497    */
498   public void setItem(int node, int index)
499   {
500     assertion(false, "setItem not supported by this iterator!");
501   }
502 
503   /**
504    *  The number of nodes in the list. The range of valid child node indices
505    * is 0 to <code>length-1</code> inclusive.
506    *
507    * @return The number of nodes in the list, always greater or equal to zero.
508    */
509   public int getLength()
510   {      
511     // Tell if this is being called from within a predicate.
512     boolean isPredicateTest = (this == m_execContext.getSubContextList());
513 
514     // And get how many total predicates are part of this step.
515     int predCount = getPredicateCount();
516     
517     // If we have already calculated the length, and the current predicate 
518     // is the first predicate, then return the length.  We don't cache 
519     // the anything but the length of the list to the first predicate.
520     if (-1 != m_length && isPredicateTest && m_predicateIndex < 1)
521         return m_length;
522     
523     // I'm a bit worried about this one, since it doesn't have the 
524     // checks found above.  I suspect it's fine.  -sb
525     if (m_foundLast)
526         return m_pos;
527         
528     // Create a clone, and count from the current position to the end 
529     // of the list, not taking into account the current predicate and 
530     // predicates after the current one.
531     int pos = (m_predicateIndex >= 0) ? getProximityPosition() : m_pos;
532               
533     LocPathIterator clone;
534 
535     try
536     {
537       clone = (LocPathIterator) clone();        
538     }
539     catch (CloneNotSupportedException   cnse)
540     {
541       return -1;
542     }
543 
544     // We want to clip off the last predicate, but only if we are a sub 
545     // context node list, NOT if we are a context list.  See pos68 test, 
546     // also test against bug4638.
547     if (predCount > 0 && isPredicateTest)
548     {
549       // Don't call setPredicateCount, because it clones and is slower.
550       clone.m_predCount = m_predicateIndex;
551       // The line above used to be:
552       // clone.m_predCount = predCount - 1;
553       // ...which looks like a dumb bug to me. -sb
554     }
555 
556     int next;
557 
558     while (DTM.NULL != (next = clone.nextNode()))
559     {
560       pos++;
561     }
562     
563     if (isPredicateTest && m_predicateIndex < 1)
564       m_length = pos;
565     
566     return pos;
567   }
568 
569   /**
570    * Tells if this NodeSetDTM is "fresh", in other words, if
571    * the first nextNode() that is called will return the
572    * first node in the set.
573    *
574    * @return true of nextNode has not been called.
575    */
576   public boolean isFresh()
577   {
578     return (m_pos == 0);
579   }
580 
581   /**
582    *  Returns the previous node in the set and moves the position of the
583    * iterator backwards in the set.
584    * @return  The previous <code>Node</code> in the set being iterated over,
585    *   or<code>null</code> if there are no more members in that set.
586    */
587   public int previousNode()
588   {
589     throw new RuntimeException  (
590       XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_CANNOT_ITERATE, null)); //"This NodeSetDTM can not iterate to a previous node!");
591   }
592 
593   /**
594    * This attribute determines which node types are presented via the
595    * iterator. The available set of constants is defined in the
596    * <code>NodeFilter</code> interface.
597    *
598    * <p>This is somewhat useless at this time, since it doesn't
599    * really return information that tells what this iterator will
600    * show.  It is here only to fullfill the DOM NodeIterator
601    * interface.</p>
602    *
603    * @return For now, always NodeFilter.SHOW_ALL & ~NodeFilter.SHOW_ENTITY_REFERENCE.
604    * @see org.w3c.dom.traversal.NodeIterator
605    */
606   public int getWhatToShow()
607   {
608 
609     // TODO: ??
610     return DTMFilter.SHOW_ALL & ~DTMFilter.SHOW_ENTITY_REFERENCE;
611   }
612 
613   /**
614    *  The filter used to screen nodes.  Not used at this time,
615    * this is here only to fullfill the DOM NodeIterator
616    * interface.
617    *
618    * @return Always null.
619    * @see org.w3c.dom.traversal.NodeIterator
620    */
621   public DTMFilter getFilter()
622   {
623     return null;
624   }
625 
626   /**
627    * The root node of the Iterator, as specified when it was created.
628    *
629    * @return The "root" of this iterator, which, in XPath terms,
630    * is the node context for this iterator.
631    */
632   public int getRoot()
633   {
634     return m_context;
635   }
636 
637   /**
638    *  The value of this flag determines whether the children of entity
639    * reference nodes are visible to the iterator. If false, they will be
640    * skipped over.
641    * <br> To produce a view of the document that has entity references
642    * expanded and does not expose the entity reference node itself, use the
643    * whatToShow flags to hide the entity reference node and set
644    * expandEntityReferences to true when creating the iterator. To produce
645    * a view of the document that has entity reference nodes but no entity
646    * expansion, use the whatToShow flags to show the entity reference node
647    * and set expandEntityReferences to false.
648    *
649    * @return Always true, since entity reference nodes are not
650    * visible in the XPath model.
651    */
652   public boolean getExpandEntityReferences()
653   {
654     return true;
655   }
656   
657   /** Control over whether it is OK for detach to reset the iterator. */
658   protected boolean m_allowDetach = true;
659   
660   /**
661    * Specify if it's OK for detach to release the iterator for reuse.
662    * 
663    * @param allowRelease true if it is OK for detach to release this iterator 
664    * for pooling.
665    */
666   public void allowDetachToRelease(boolean allowRelease)
667   {
668     m_allowDetach = allowRelease;
669   }
670 
671   /**
672    *  Detaches the iterator from the set which it iterated over, releasing
673    * any computational resources and placing the iterator in the INVALID
674    * state. After<code>detach</code> has been invoked, calls to
675    * <code>nextNode</code> or<code>previousNode</code> will raise the
676    * exception INVALID_STATE_ERR.
677    */
678   public void detach()
679   {    
680     if(m_allowDetach)
681     {
682       // sb: allow reusing of cached nodes when possible?
683       // m_cachedNodes = null;
684       m_execContext = null;
685       // m_prefixResolver = null;  sb: Why would this ever want to be null?
686       m_cdtm = null;
687       m_length = -1;
688       m_pos = 0;
689       m_lastFetched = DTM.NULL;
690       m_context = DTM.NULL;
691       m_currentContextNode = DTM.NULL;
692       
693       m_clones.freeInstance(this);
694     }
695   }
696   
697   /**
698    * Reset the iterator.
699    */
700   public void reset()
701   {
702     assertion(false, "This iterator can not reset!");
703   }
704 
705   /**
706    * Get a cloned Iterator that is reset to the beginning
707    * of the query.
708    *
709    * @return A cloned NodeIterator set of the start of the query.
710    *
711    * @throws CloneNotSupportedException
712    */
713   public DTMIterator cloneWithReset() throws CloneNotSupportedException  
714   {
715     LocPathIterator clone;
716 //    clone = (LocPathIterator) clone();
717     clone = (LocPathIterator)m_clones.getInstanceOrThrow();
718     clone.m_execContext = m_execContext;
719     clone.m_cdtm = m_cdtm;
720     
721     clone.m_context = m_context;
722     clone.m_currentContextNode = m_currentContextNode;
723     clone.m_stackFrame = m_stackFrame;
724 
725     // clone.reset();
726 
727     return clone;
728   }
729 
730 //  /**
731 //   * Get a cloned LocPathIterator that holds the same
732 //   * position as this iterator.
733 //   *
734 //   * @return A clone of this iterator that holds the same node position.
735 //   *
736 //   * @throws CloneNotSupportedException
737 //   */
738 //  public Object clone() throws CloneNotSupportedException
739 //  {
740 //
741 //    LocPathIterator clone = (LocPathIterator) super.clone();
742 //
743 //    return clone;
744 //  }
745 
746   /**
747    *  Returns the next node in the set and advances the position of the
748    * iterator in the set. After a NodeIterator is created, the first call
749    * to nextNode() returns the first node in the set.
750    * @return  The next <code>Node</code> in the set being iterated over, or
751    *   <code>null</code> if there are no more members in that set.
752    */
753   public abstract int nextNode();
754 
755   /**
756    * Bottleneck the return of a next node, to make returns
757    * easier from nextNode().
758    *
759    * @param nextNode The next node found, may be null.
760    *
761    * @return The same node that was passed as an argument.
762    */
763   protected int returnNextNode(int nextNode)
764   {
765 
766     if (DTM.NULL != nextNode)
767     {
768       m_pos++;
769     }
770 
771     m_lastFetched = nextNode;
772 
773     if (DTM.NULL == nextNode)
774       m_foundLast = true;
775 
776     return nextNode;
777   }
778 
779   /**
780    * Return the last fetched node.  Needed to support the UnionPathIterator.
781    *
782    * @return The last fetched node, or null if the last fetch was null.
783    */
784   public int getCurrentNode()
785   {
786     return m_lastFetched;
787   }
788 
789   /**
790    * If an index is requested, NodeSetDTM will call this method
791    * to run the iterator to the index.  By default this sets
792    * m_next to the index.  If the index argument is -1, this
793    * signals that the iterator should be run to the end.
794    *
795    * @param index The index to run to, or -1 if the iterator
796    * should run to the end.
797    */
798   public void runTo(int index)
799   {
800 
801     if (m_foundLast || ((index >= 0) && (index <= getCurrentPos())))
802       return;
803 
804     int n;
805 
806     if (-1 == index)
807     {
808       while (DTM.NULL != (n = nextNode()));
809     }
810     else
811     {
812       while (DTM.NULL != (n = nextNode()))
813       {
814         if (getCurrentPos() >= index)
815           break;
816       }
817     }
818   }
819 
820   /**
821    * Tells if we've found the last node yet.
822    *
823    * @return true if the last nextNode returned null.
824    */
825   public final boolean getFoundLast()
826   {
827     return m_foundLast;
828   }
829 
830   /**
831    * The XPath execution context we are operating on.
832    *
833    * @return XPath execution context this iterator is operating on,
834    * or null if setRoot has not been called.
835    */
836   public final XPathContext getXPathContext()
837   {
838     return m_execContext;
839   }
840 
841   /**
842    * The node context for the iterator.
843    *
844    * @return The node context, same as getRoot().
845    */
846   public final int getContext()
847   {
848     return m_context;
849   }
850 
851   /**
852    * The node context from where the expression is being
853    * executed from (i.e. for current() support).
854    *
855    * @return The top-level node context of the entire expression.
856    */
857   public final int getCurrentContextNode()
858   {
859     return m_currentContextNode;
860   }
861 
862   /**
863    * Set the current context node for this iterator.
864    *
865    * @param n Must be a non-null reference to the node context.
866    */
867   public final void setCurrentContextNode(int n)
868   {
869     m_currentContextNode = n;
870   }
871   
872 //  /**
873 //   * Set the current context node for this iterator.
874 //   *
875 //   * @param n Must be a non-null reference to the node context.
876 //   */
877 //  public void setRoot(int n)
878 //  {
879 //    m_context = n;
880 //    m_cdtm = m_execContext.getDTM(n);
881 //  }
882 
883   /**
884    * Return the saved reference to the prefix resolver that
885    * was in effect when this iterator was created.
886    *
887    * @return The prefix resolver or this iterator, which may be null.
888    */
889   public final PrefixResolver getPrefixResolver()
890   {
891     if(null == m_prefixResolver)
892     {
893         m_prefixResolver = (PrefixResolver)getExpressionOwner();
894     }
895 
896     return m_prefixResolver;
897   }
898         
899 //  /**
900 //   * Get the analysis pattern built by the WalkerFactory.
901 //   *
902 //   * @return The analysis pattern built by the WalkerFactory.
903 //   */
904 //  int getAnalysis()
905 //  {
906 //    return m_analysis;
907 //  }
908 
909 //  /**
910 //   * Set the analysis pattern built by the WalkerFactory.
911 //   *
912 //   * @param a The analysis pattern built by the WalkerFactory.
913 //   */
914 //  void setAnalysis(int a)
915 //  {
916 //    m_analysis = a;
917 //  }
918 
919   /**
920    * @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
921    */
922   public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
923   {
924         if(visitor.visitLocationPath(owner, this))
925         {
926             visitor.visitStep(owner, this);
927             callPredicateVisitors(visitor);
928         }
929   }  
930 
931   
932   //============= State Data =============
933   
934   /** 
935    * The pool for cloned iterators.  Iterators need to be cloned
936    * because the hold running state, and thus the original iterator
937    * expression from the stylesheet pool can not be used.          
938    */
939   transient protected IteratorPool m_clones = new IteratorPool(this);
940   
941   /** 
942    * The dtm of the context node.  Careful about using this... it may not 
943    * be the dtm of the current node.
944    */
945   transient protected DTM m_cdtm;
946   
947   /**
948    * The stack frame index for this iterator.
949    */
950   transient int m_stackFrame = -1;
951 
952   /**
953    * Value determined at compile time, indicates that this is an
954    * iterator at the top level of the expression, rather than inside
955    * a predicate.
956    * @serial
957    */
958   private boolean m_isTopLevel = false;
959 
960   /** The last node that was fetched, usually by nextNode. */
961   transient public int m_lastFetched = DTM.NULL;
962 
963   /**
964    * The context node for this iterator, which doesn't change through
965    * the course of the iteration.
966    */
967   transient protected int m_context = DTM.NULL;
968 
969   /**
970    * The node context from where the expression is being
971    * executed from (i.e. for current() support).  Different
972    * from m_context in that this is the context for the entire
973    * expression, rather than the context for the subexpression.
974    */
975   transient protected int m_currentContextNode = DTM.NULL;
976   
977   /**
978    * The current position of the context node.
979    */
980   transient protected int m_pos = 0;
981   
982   transient protected int m_length = -1;
983 
984   /**
985    * Fast access to the current prefix resolver.  It isn't really
986    * clear that this is needed.
987    * @serial
988    */
989   private PrefixResolver m_prefixResolver;
990 
991   /**
992    * The XPathContext reference, needed for execution of many
993    * operations.
994    */
995   transient protected XPathContext m_execContext;
996   
997   /**
998    * Returns true if all the nodes in the iteration well be returned in document 
999    * order.
1000   * 
1001   * @return true as a default.
1002   */
1003  public boolean isDocOrdered()
1004  {
1005    return true;
1006  }
1007  
1008  /**
1009   * Returns the axis being iterated, if it is known.
1010   * 
1011   * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple 
1012   * types.
1013   */
1014  public int getAxis()
1015  {
1016    return -1;
1017  }
1018
1019
1020//  /**
1021//   * The analysis pattern built by the WalkerFactory.
1022//   * TODO: Move to LocPathIterator.
1023//   * @see org.apache.xpath.axes.WalkerFactory
1024//   * @serial
1025//   */
1026//  protected int m_analysis = 0x00000000;
1027  /**
1028   * @see PredicatedNodeTest#getLastPos(XPathContext)
1029   */
1030  public int getLastPos(XPathContext xctxt)
1031  {
1032    return getLength();
1033  }
1034
1035}
1036
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