1/*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the  "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 *     http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18/*
19 * $Id: MatchPatternIterator.java 469314 2006-10-30 23:31:59Z minchau $
20 */
21package org.apache.xpath.axes;
22
23import org.apache.xml.dtm.Axis;
24import org.apache.xml.dtm.DTM;
25import org.apache.xml.dtm.DTMAxisTraverser;
26import org.apache.xml.dtm.DTMIterator;
27import org.apache.xpath.XPathContext;
28import org.apache.xpath.compiler.Compiler;
29import org.apache.xpath.compiler.OpMap;
30import org.apache.xpath.objects.XObject;
31import org.apache.xpath.patterns.NodeTest;
32import org.apache.xpath.patterns.StepPattern;
33
34/**
35 * This class treats a
36 * <a href="http://www.w3.org/TR/xpath#location-paths">LocationPath</a> as a
37 * filtered iteration over the tree, evaluating each node in a super axis
38 * traversal against the LocationPath interpreted as a match pattern.  This
39 * class is useful to find nodes in document order that are complex paths
40 * whose steps probably criss-cross each other.
41 */
42public class MatchPatternIterator extends LocPathIterator
43{
44    static final long serialVersionUID = -5201153767396296474L;
45
46  /** This is the select pattern, translated into a match pattern. */
47  protected StepPattern m_pattern;
48
49  /** The traversal axis from where the nodes will be filtered. */
50  protected int m_superAxis = -1;
51
52  /** The DTM inner traversal class, that corresponds to the super axis. */
53  protected DTMAxisTraverser m_traverser;
54
55  /** DEBUG flag for diagnostic dumps. */
56  private static final boolean DEBUG = false;
57
58//  protected int m_nsElemBase = DTM.NULL;
59
60  /**
61   * Create a LocPathIterator object, including creation
62   * of step walkers from the opcode list, and call back
63   * into the Compiler to create predicate expressions.
64   *
65   * @param compiler The Compiler which is creating
66   * this expression.
67   * @param opPos The position of this iterator in the
68   * opcode list from the compiler.
69   * @param analysis Analysis bits that give general information about the
70   * LocationPath.
71   *
72   * @throws javax.xml.transform.TransformerException
73   */
74  MatchPatternIterator(Compiler compiler, int opPos, int analysis)
75          throws javax.xml.transform.TransformerException
76  {
77
78    super(compiler, opPos, analysis, false);
79
80    int firstStepPos = OpMap.getFirstChildPos(opPos);
81
82    m_pattern = WalkerFactory.loadSteps(this, compiler, firstStepPos, 0);
83
84    boolean fromRoot = false;
85    boolean walkBack = false;
86    boolean walkDescendants = false;
87    boolean walkAttributes = false;
88
89    if (0 != (analysis & (WalkerFactory.BIT_ROOT |
90                          WalkerFactory.BIT_ANY_DESCENDANT_FROM_ROOT)))
91      fromRoot = true;
92
93    if (0 != (analysis
94              & (WalkerFactory.BIT_ANCESTOR
95                 | WalkerFactory.BIT_ANCESTOR_OR_SELF
96                 | WalkerFactory.BIT_PRECEDING
97                 | WalkerFactory.BIT_PRECEDING_SIBLING
98                 | WalkerFactory.BIT_FOLLOWING
99                 | WalkerFactory.BIT_FOLLOWING_SIBLING
100                 | WalkerFactory.BIT_PARENT | WalkerFactory.BIT_FILTER)))
101      walkBack = true;
102
103    if (0 != (analysis
104              & (WalkerFactory.BIT_DESCENDANT_OR_SELF
105                 | WalkerFactory.BIT_DESCENDANT
106                 | WalkerFactory.BIT_CHILD)))
107      walkDescendants = true;
108
109    if (0 != (analysis
110              & (WalkerFactory.BIT_ATTRIBUTE | WalkerFactory.BIT_NAMESPACE)))
111      walkAttributes = true;
112
113    if(false || DEBUG)
114    {
115      System.out.print("analysis: "+Integer.toBinaryString(analysis));
116      System.out.println(", "+WalkerFactory.getAnalysisString(analysis));
117    }
118
119    if(fromRoot || walkBack)
120    {
121      if(walkAttributes)
122      {
123        m_superAxis = Axis.ALL;
124      }
125      else
126      {
127        m_superAxis = Axis.DESCENDANTSFROMROOT;
128      }
129    }
130    else if(walkDescendants)
131    {
132      if(walkAttributes)
133      {
134        m_superAxis = Axis.ALLFROMNODE;
135      }
136      else
137      {
138        m_superAxis = Axis.DESCENDANTORSELF;
139      }
140    }
141    else
142    {
143      m_superAxis = Axis.ALL;
144    }
145    if(false || DEBUG)
146    {
147      System.out.println("axis: "+Axis.getNames(m_superAxis));
148    }
149
150  }
151
152
153  /**
154   * Initialize the context values for this expression
155   * after it is cloned.
156   *
157   * @param context The XPath runtime context for this
158   * transformation.
159   */
160  public void setRoot(int context, Object environment)
161  {
162    super.setRoot(context, environment);
163    m_traverser = m_cdtm.getAxisTraverser(m_superAxis);
164  }
165
166  /**
167   *  Detaches the iterator from the set which it iterated over, releasing
168   * any computational resources and placing the iterator in the INVALID
169   * state. After<code>detach</code> has been invoked, calls to
170   * <code>nextNode</code> or<code>previousNode</code> will raise the
171   * exception INVALID_STATE_ERR.
172   */
173  public void detach()
174  {
175    if(m_allowDetach)
176    {
177      m_traverser = null;
178
179      // Always call the superclass detach last!
180      super.detach();
181    }
182  }
183
184  /**
185   * Get the next node via getNextXXX.  Bottlenecked for derived class override.
186   * @return The next node on the axis, or DTM.NULL.
187   */
188  protected int getNextNode()
189  {
190    m_lastFetched = (DTM.NULL == m_lastFetched)
191                     ? m_traverser.first(m_context)
192                     : m_traverser.next(m_context, m_lastFetched);
193    return m_lastFetched;
194  }
195
196  /**
197   *  Returns the next node in the set and advances the position of the
198   * iterator in the set. After a NodeIterator is created, the first call
199   * to nextNode() returns the first node in the set.
200   * @return  The next <code>Node</code> in the set being iterated over, or
201   *   <code>null</code> if there are no more members in that set.
202   */
203  public int nextNode()
204  {
205  	if(m_foundLast)
206  		return DTM.NULL;
207
208    int next;
209
210    org.apache.xpath.VariableStack vars;
211    int savedStart;
212    if (-1 != m_stackFrame)
213    {
214      vars = m_execContext.getVarStack();
215
216      // These three statements need to be combined into one operation.
217      savedStart = vars.getStackFrame();
218
219      vars.setStackFrame(m_stackFrame);
220    }
221    else
222    {
223      // Yuck.  Just to shut up the compiler!
224      vars = null;
225      savedStart = 0;
226    }
227
228    try
229    {
230      if(DEBUG)
231        System.out.println("m_pattern"+m_pattern.toString());
232
233      do
234      {
235        next = getNextNode();
236
237        if (DTM.NULL != next)
238        {
239          if(DTMIterator.FILTER_ACCEPT == acceptNode(next, m_execContext))
240            break;
241          else
242            continue;
243        }
244        else
245          break;
246      }
247      while (next != DTM.NULL);
248
249      if (DTM.NULL != next)
250      {
251        if(DEBUG)
252        {
253          System.out.println("next: "+next);
254          System.out.println("name: "+m_cdtm.getNodeName(next));
255        }
256        incrementCurrentPos();
257
258        return next;
259      }
260      else
261      {
262        m_foundLast = true;
263
264        return DTM.NULL;
265      }
266    }
267    finally
268    {
269      if (-1 != m_stackFrame)
270      {
271        // These two statements need to be combined into one operation.
272        vars.setStackFrame(savedStart);
273      }
274    }
275
276  }
277
278  /**
279   *  Test whether a specified node is visible in the logical view of a
280   * TreeWalker or NodeIterator. This function will be called by the
281   * implementation of TreeWalker and NodeIterator; it is not intended to
282   * be called directly from user code.
283   * @param n  The node to check to see if it passes the filter or not.
284   * @return  a constant to determine whether the node is accepted,
285   *   rejected, or skipped, as defined  above .
286   */
287  public short acceptNode(int n, XPathContext xctxt)
288  {
289
290    try
291    {
292      xctxt.pushCurrentNode(n);
293      xctxt.pushIteratorRoot(m_context);
294      if(DEBUG)
295      {
296        System.out.println("traverser: "+m_traverser);
297        System.out.print("node: "+n);
298        System.out.println(", "+m_cdtm.getNodeName(n));
299        // if(m_cdtm.getNodeName(n).equals("near-east"))
300        System.out.println("pattern: "+m_pattern.toString());
301        m_pattern.debugWhatToShow(m_pattern.getWhatToShow());
302      }
303
304      XObject score = m_pattern.execute(xctxt);
305
306      if(DEBUG)
307      {
308        // System.out.println("analysis: "+Integer.toBinaryString(m_analysis));
309        System.out.println("score: "+score);
310        System.out.println("skip: "+(score == NodeTest.SCORE_NONE));
311      }
312
313      // System.out.println("\n::acceptNode - score: "+score.num()+"::");
314      return (score == NodeTest.SCORE_NONE) ? DTMIterator.FILTER_SKIP
315                    : DTMIterator.FILTER_ACCEPT;
316    }
317    catch (javax.xml.transform.TransformerException se)
318    {
319
320      // TODO: Fix this.
321      throw new RuntimeException(se.getMessage());
322    }
323    finally
324    {
325      xctxt.popCurrentNode();
326      xctxt.popIteratorRoot();
327    }
328
329  }
330
331}
332