Step


1   /*
2    * Copyright 2001-2004 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: Step.java,v 1.1.2.2 2006/11/10 22:07:02 spericas Exp $
18   */
19  
20  package com.sun.org.apache.xalan.internal.xsltc.compiler;
21  
22  import java.util.Vector  ;
23  
24  import com.sun.org.apache.bcel.internal.generic.CHECKCAST;
25  import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
26  import com.sun.org.apache.bcel.internal.generic.ICONST;
27  import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
28  import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
29  import com.sun.org.apache.bcel.internal.generic.InstructionList;
30  import com.sun.org.apache.bcel.internal.generic.NEW;
31  import com.sun.org.apache.bcel.internal.generic.PUSH;
32  import com.sun.org.apache.xalan.internal.xsltc.DOM;
33  import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
34  import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
35  import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
36  import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
37  import com.sun.org.apache.xalan.internal.xsltc.dom.Axis;
38  import com.sun.org.apache.xml.internal.dtm.DTM;
39  
40  /**
41   * @author Jacek Ambroziak
42   * @author Santiago Pericas-Geertsen
43   * @author Morten Jorgensen
44   */
45  final class Step extends RelativeLocationPath {
46  
47      /**
48       * This step's axis as defined in class Axis.
49       */
50      private int _axis;
51  
52      /**
53       * A vector of predicates (filters) defined on this step - may be null
54       */
55      private Vector   _predicates;
56  
57      /**
58       * Some simple predicates can be handled by this class (and not by the
59       * Predicate class) and will be removed from the above vector as they are
60       * handled. We use this boolean to remember if we did have any predicates.
61       */
62      private boolean _hadPredicates = false;
63  
64      /**
65       * Type of the node test.
66       */
67      private int _nodeType;
68  
69      public Step(int axis, int nodeType, Vector   predicates) {
70      _axis = axis;
71      _nodeType = nodeType;
72      _predicates = predicates;
73      }
74  
75      /**
76       * Set the parser for this element and all child predicates
77       */
78      public void setParser(Parser parser) {
79      super.setParser(parser);
80      if (_predicates != null) {
81          final int n = _predicates.size();
82          for (int i = 0; i < n; i++) {
83          final Predicate exp = (Predicate)_predicates.elementAt(i);
84          exp.setParser(parser);
85          exp.setParent(this);
86          }
87      }
88      }
89      
90      /**
91       * Define the axis (defined in Axis class) for this step
92       */
93      public int getAxis() {
94      return _axis;
95      }
96      
97      /**
98       * Get the axis (defined in Axis class) for this step
99       */
100     public void setAxis(int axis) {
101     _axis = axis;
102     }
103 
104     /**
105      * Returns the node-type for this step
106      */
107     public int getNodeType() {
108     return _nodeType;
109     }
110 
111     /**
112      * Returns the vector containing all predicates for this step.
113      */
114     public Vector   getPredicates() {
115     return _predicates;
116     }
117 
118     /**
119      * Returns the vector containing all predicates for this step.
120      */
121     public void addPredicates(Vector   predicates) {
122     if (_predicates == null) {
123         _predicates = predicates;
124     }
125     else {
126         _predicates.addAll(predicates);
127     }
128     }
129 
130     /**
131      * Returns 'true' if this step has a parent pattern.
132      * This method will return 'false' if this step occurs on its own under
133      * an element like <xsl:for-each> or <xsl:apply-templates>.
134      */
135     private boolean hasParentPattern() {
136     final SyntaxTreeNode parent = getParent();
137     return (parent instanceof ParentPattern ||
138         parent instanceof ParentLocationPath ||
139         parent instanceof UnionPathExpr ||
140         parent instanceof FilterParentPath);
141     }
142     
143     /**
144      * Returns 'true' if this step has a parent location path.
145      */
146     private boolean hasParentLocationPath() {
147     return getParent() instanceof ParentLocationPath;
148     }
149     
150     /**
151      * Returns 'true' if this step has any predicates
152      */
153     private boolean hasPredicates() {
154     return _predicates != null && _predicates.size() > 0;
155     }
156 
157     /**
158      * Returns 'true' if this step is used within a predicate
159      */
160     private boolean isPredicate() {
161     SyntaxTreeNode parent = this;
162     while (parent != null) {
163         parent = parent.getParent();
164         if (parent instanceof Predicate) return true;
165     }
166     return false;
167     }
168 
169     /**
170      * True if this step is the abbreviated step '.'
171      */
172     public boolean isAbbreviatedDot() {
173     return _nodeType == NodeTest.ANODE && _axis == Axis.SELF;
174     }
175 
176 
177     /**
178      * True if this step is the abbreviated step '..'
179      */
180     public boolean isAbbreviatedDDot() {
181     return _nodeType == NodeTest.ANODE && _axis == Axis.PARENT;
182     }
183 
184     /**
185      * Type check this step. The abbreviated steps '.' and '@attr' are
186      * assigned type node if they have no predicates. All other steps 
187      * have type node-set.
188      */
189     public Type typeCheck(SymbolTable stable) throws TypeCheckError {
190 
191     // Save this value for later - important for testing for special
192     // combinations of steps and patterns than can be optimised
193     _hadPredicates = hasPredicates();
194 
195     // Special case for '.'
196     //   in the case where '.' has a context such as book/. 
197     //   or .[false()] we can not optimize the nodeset to a single node. 
198     if (isAbbreviatedDot()) {
199         _type = (hasParentPattern() || hasPredicates() || hasParentLocationPath()) ? 
200         Type.NodeSet : Type.Node;
201     }
202     else {
203         _type = Type.NodeSet;
204     }
205 
206     // Type check all predicates (expressions applied to the step)
207     if (_predicates != null) {
208         final int n = _predicates.size();
209         for (int i = 0; i < n; i++) {
210         final Expression pred = (Expression)_predicates.elementAt(i);
211         pred.typeCheck(stable);
212         }
213     }
214 
215     // Return either Type.Node or Type.NodeSet
216     return _type;
217     }
218 
219     /**
220      * Translate a step by pushing the appropriate iterator onto the stack.
221      * The abbreviated steps '.' and '@attr' do not create new iterators
222      * if they are not part of a LocationPath and have no filters.
223      * In these cases a node index instead of an iterator is pushed
224      * onto the stack.
225      */
226     public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
227     final ConstantPoolGen cpg = classGen.getConstantPool();
228     final InstructionList il = methodGen.getInstructionList();
229 
230     if (hasPredicates()) {
231         translatePredicates(classGen, methodGen);
232     } else {
233             int star = 0;
234             String   name = null;
235             final XSLTC xsltc = getParser().getXSLTC();
236 
237             if (_nodeType >= DTM.NTYPES) {
238         final Vector   ni = xsltc.getNamesIndex();
239         
240                 name = (String  )ni.elementAt(_nodeType-DTM.NTYPES);
241                 star = name.lastIndexOf('*');
242             }
243 
244         // If it is an attribute, but not '@*', '@pre:*' or '@node()',
245             // and has no parent
246         if (_axis == Axis.ATTRIBUTE && _nodeType != NodeTest.ATTRIBUTE
247         && _nodeType != NodeTest.ANODE && !hasParentPattern()
248                 && star == 0)
249         {
250         int iter = cpg.addInterfaceMethodref(DOM_INTF,
251                              "getTypedAxisIterator",
252                              "(II)"+NODE_ITERATOR_SIG);
253         il.append(methodGen.loadDOM());
254         il.append(new PUSH(cpg, Axis.ATTRIBUTE));
255         il.append(new PUSH(cpg, _nodeType));
256         il.append(new INVOKEINTERFACE(iter, 3));
257         return;
258         }
259 
260         SyntaxTreeNode parent = getParent();
261         // Special case for '.'
262         if (isAbbreviatedDot()) {
263         if (_type == Type.Node) {
264             // Put context node on stack if using Type.Node
265             il.append(methodGen.loadContextNode());
266         }
267         else {
268             if (parent instanceof ParentLocationPath){
269             // Wrap the context node in a singleton iterator if not.
270             int init = cpg.addMethodref(SINGLETON_ITERATOR,
271                             "<init>",
272                             "("+NODE_SIG+")V");
273             il.append(new NEW(cpg.addClass(SINGLETON_ITERATOR)));
274             il.append(DUP);
275             il.append(methodGen.loadContextNode());
276             il.append(new INVOKESPECIAL(init));
277             } else {
278             // DOM.getAxisIterator(int axis);
279             int git = cpg.addInterfaceMethodref(DOM_INTF,
280                         "getAxisIterator",
281                         "(I)"+NODE_ITERATOR_SIG);
282             il.append(methodGen.loadDOM());
283             il.append(new PUSH(cpg, _axis));
284             il.append(new INVOKEINTERFACE(git, 2));
285             }
286         }
287         return;
288         }
289             
290         // Special case for /foo/*/bar
291         if ((parent instanceof ParentLocationPath) &&
292         (parent.getParent() instanceof ParentLocationPath)) {
293         if ((_nodeType == NodeTest.ELEMENT) && (!_hadPredicates)) {
294             _nodeType = NodeTest.ANODE;
295         }
296         }
297 
298         // "ELEMENT" or "*" or "@*" or ".." or "@attr" with a parent.
299         switch (_nodeType) {
300         case NodeTest.ATTRIBUTE:
301         _axis = Axis.ATTRIBUTE;
302         case NodeTest.ANODE:
303         // DOM.getAxisIterator(int axis);
304         int git = cpg.addInterfaceMethodref(DOM_INTF,
305                             "getAxisIterator",
306                             "(I)"+NODE_ITERATOR_SIG);
307         il.append(methodGen.loadDOM());
308         il.append(new PUSH(cpg, _axis));
309         il.append(new INVOKEINTERFACE(git, 2));
310         break;
311         default:
312         if (star > 1) {
313             final String   namespace;
314             if (_axis == Axis.ATTRIBUTE)
315             namespace = name.substring(0,star-2);
316             else
317             namespace = name.substring(0,star-1);
318 
319             final int nsType = xsltc.registerNamespace(namespace);
320             final int ns = cpg.addInterfaceMethodref(DOM_INTF,
321                             "getNamespaceAxisIterator",
322                             "(II)"+NODE_ITERATOR_SIG);
323             il.append(methodGen.loadDOM());
324             il.append(new PUSH(cpg, _axis));
325             il.append(new PUSH(cpg, nsType));
326             il.append(new INVOKEINTERFACE(ns, 3));
327             break;
328         }
329         case NodeTest.ELEMENT:
330         // DOM.getTypedAxisIterator(int axis, int type);
331         final int ty = cpg.addInterfaceMethodref(DOM_INTF,
332                         "getTypedAxisIterator",
333                         "(II)"+NODE_ITERATOR_SIG);
334         // Get the typed iterator we're after
335         il.append(methodGen.loadDOM());
336         il.append(new PUSH(cpg, _axis));
337         il.append(new PUSH(cpg, _nodeType));
338         il.append(new INVOKEINTERFACE(ty, 3));
339 
340         break;
341         }
342     }
343     }
344 
345 
346     /**
347      * Translate a sequence of predicates. Each predicate is translated
348      * by constructing an instance of <code>CurrentNodeListIterator</code>
349      * which is initialized from another iterator (recursive call),
350      * a filter and a closure (call to translate on the predicate) and "this". 
351      */
352     public void translatePredicates(ClassGenerator classGen,
353                     MethodGenerator methodGen) {
354     final ConstantPoolGen cpg = classGen.getConstantPool();
355     final InstructionList il = methodGen.getInstructionList();
356 
357     int idx = 0;
358 
359     if (_predicates.size() == 0) {
360         translate(classGen, methodGen);
361     }
362     else {
363         final Predicate predicate = (Predicate)_predicates.lastElement();
364         _predicates.remove(predicate);
365 
366         // Special case for predicates that can use the NodeValueIterator
367         // instead of an auxiliary class. Certain path/predicates pairs
368         // are translated into a base path, on top of which we place a
369         // node value iterator that tests for the desired value:
370         //   foo[@attr = 'str']  ->  foo/@attr + test(value='str')
371         //   foo[bar = 'str']    ->  foo/bar + test(value='str')
372         //   foo/bar[. = 'str']  ->  foo/bar + test(value='str')
373         if (predicate.isNodeValueTest()) {
374         Step step = predicate.getStep();
375 
376         il.append(methodGen.loadDOM());
377         // If the predicate's Step is simply '.' we translate this Step
378         // and place the node test on top of the resulting iterator
379         if (step.isAbbreviatedDot()) {
380             translate(classGen, methodGen);
381             il.append(new ICONST(DOM.RETURN_CURRENT));
382         }
383         // Otherwise we create a parent location path with this Step and
384         // the predicates Step, and place the node test on top of that
385         else {
386             ParentLocationPath path = new ParentLocationPath(this, step);
387                     _parent = step._parent = path;      // Force re-parenting
388                     
389             try {
390             path.typeCheck(getParser().getSymbolTable());
391             }
392             catch (TypeCheckError e) { }
393             path.translate(classGen, methodGen);
394             il.append(new ICONST(DOM.RETURN_PARENT));
395         }
396         predicate.translate(classGen, methodGen);
397         idx = cpg.addInterfaceMethodref(DOM_INTF,
398                         GET_NODE_VALUE_ITERATOR,
399                         GET_NODE_VALUE_ITERATOR_SIG);
400         il.append(new INVOKEINTERFACE(idx, 5));
401         }            
402         // Handle '//*[n]' expression
403         else if (predicate.isNthDescendant()) {
404         il.append(methodGen.loadDOM());
405         // il.append(new ICONST(NodeTest.ELEMENT));
406         il.append(new ICONST(predicate.getPosType()));
407         predicate.translate(classGen, methodGen);
408         il.append(new ICONST(0));
409         idx = cpg.addInterfaceMethodref(DOM_INTF,
410                         "getNthDescendant",
411                         "(IIZ)"+NODE_ITERATOR_SIG);
412         il.append(new INVOKEINTERFACE(idx, 4));
413         }
414         // Handle 'elem[n]' expression
415         else if (predicate.isNthPositionFilter()) {
416         idx = cpg.addMethodref(NTH_ITERATOR_CLASS,
417                        "<init>",
418                        "("+NODE_ITERATOR_SIG+"I)V");
419         il.append(new NEW(cpg.addClass(NTH_ITERATOR_CLASS)));
420         il.append(DUP);
421         translatePredicates(classGen, methodGen); // recursive call
422         predicate.translate(classGen, methodGen);
423         il.append(new INVOKESPECIAL(idx));
424         }
425         else {
426         idx = cpg.addMethodref(CURRENT_NODE_LIST_ITERATOR,
427                        "<init>",
428                        "("
429                        + NODE_ITERATOR_SIG
430                        + CURRENT_NODE_LIST_FILTER_SIG
431                        + NODE_SIG
432                        + TRANSLET_SIG
433                        + ")V");
434         // create new CurrentNodeListIterator
435         il.append(new NEW(cpg.addClass(CURRENT_NODE_LIST_ITERATOR)));
436         il.append(DUP);
437         translatePredicates(classGen, methodGen); // recursive call
438         predicate.translateFilter(classGen, methodGen);
439         
440         il.append(methodGen.loadCurrentNode());
441         il.append(classGen.loadTranslet());
442         if (classGen.isExternal()) {
443             final String   className = classGen.getClassName();
444             il.append(new CHECKCAST(cpg.addClass(className)));
445         }
446         il.append(new INVOKESPECIAL(idx));
447         }
448     }
449     }
450 
451     /**
452      * Returns a string representation of this step.
453      */
454     public String   toString() {
455     final StringBuffer   buffer = new StringBuffer  ("step(\"");
456     buffer.append(Axis.names[_axis]).append("\", ").append(_nodeType);
457     if (_predicates != null) {
458         final int n = _predicates.size();
459         for (int i = 0; i < n; i++) {
460         final Predicate pred = (Predicate)_predicates.elementAt(i);
461         buffer.append(", ").append(pred.toString());
462         }
463     }
464     return buffer.append(')').toString();
465     }
466 }
467
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags