Source Code Cross Referenced for LocationPathPattern.java in  » XML » saxonb » net » sf » saxon » pattern » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » XML » saxonb » net.sf.saxon.pattern 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package net.sf.saxon.pattern;
002:
003:        import net.sf.saxon.expr.*;
004:        import net.sf.saxon.om.*;
005:        import net.sf.saxon.style.ExpressionContext;
006:        import net.sf.saxon.trace.Location;
007:        import net.sf.saxon.trans.DynamicError;
008:        import net.sf.saxon.trans.StaticError;
009:        import net.sf.saxon.trans.XPathException;
010:        import net.sf.saxon.type.ItemType;
011:        import net.sf.saxon.type.Type;
012:        import net.sf.saxon.type.TypeHierarchy;
013:        import net.sf.saxon.value.BooleanValue;
014:        import net.sf.saxon.value.IntegerValue;
015:
016:        import java.util.Arrays;
017:        import java.util.Collections;
018:        import java.util.Iterator;
019:
020:        /**
021:         * A LocationPathPattern represents a path, for example of the form A/B/C... The components are represented
022:         * as a linked list, each component pointing to its predecessor
023:         */
024:
025:        public final class LocationPathPattern extends Pattern {
026:
027:            // the following public variables are exposed to the ExpressionParser
028:
029:            public Pattern parentPattern = null;
030:            public Pattern ancestorPattern = null;
031:            public NodeTest nodeTest = AnyNodeTest.getInstance();
032:            protected Expression[] filters = null;
033:            protected int numberOfFilters = 0;
034:            protected Expression equivalentExpr = null;
035:            protected boolean firstElementPattern = false;
036:            protected boolean lastElementPattern = false;
037:            protected boolean specialFilter = false;
038:            private Expression variableBinding = null;
039:            private NodeTest refinedNodeTest = null;
040:
041:            /**
042:             * Add a filter to the pattern (while under construction)
043:             * @param filter The predicate (a boolean expression or numeric expression) to be added
044:             */
045:
046:            public void addFilter(Expression filter) {
047:                if (filters == null) {
048:                    filters = new Expression[3];
049:                } else if (numberOfFilters == filters.length) {
050:                    Expression[] f2 = new Expression[numberOfFilters * 2];
051:                    System.arraycopy(filters, 0, f2, 0, numberOfFilters);
052:                    filters = f2;
053:                }
054:                filters[numberOfFilters++] = filter;
055:                ExpressionTool.makeParentReferences(filter);
056:                if (filter instanceof  ComputedExpression) {
057:                    ((ComputedExpression) filter).setParentExpression(this );
058:                }
059:            }
060:
061:            /**
062:             * Simplify the pattern: perform any context-independent optimisations
063:             */
064:
065:            public Pattern simplify(StaticContext env) throws XPathException {
066:
067:                // detect the simple cases: no parent or ancestor pattern, no predicates
068:
069:                if (parentPattern == null && ancestorPattern == null
070:                        && filters == null && !firstElementPattern
071:                        && !lastElementPattern) {
072:                    NodeTestPattern ntp = new NodeTestPattern(nodeTest);
073:                    ntp.setSystemId(getSystemId());
074:                    ntp.setLineNumber(getLineNumber());
075:                    return ntp;
076:                }
077:
078:                // simplify each component of the pattern
079:
080:                if (parentPattern != null) {
081:                    parentPattern = parentPattern.simplify(env);
082:                } else if (ancestorPattern != null) {
083:                    ancestorPattern = ancestorPattern.simplify(env);
084:                }
085:
086:                if (filters != null) {
087:                    for (int i = numberOfFilters - 1; i >= 0; i--) {
088:                        Expression filter = filters[i];
089:                        filter = filter.simplify(env);
090:                        filters[i] = filter;
091:                        int dep = filter.getDependencies();
092:                        if ((dep & StaticProperty.DEPENDS_ON_CURRENT_GROUP) != 0) {
093:                            String errorCode = "XTSE1060";
094:                            String function = "current-group()";
095:                            if (toString().indexOf("current-grouping-key") >= 0) {
096:                                errorCode = "XTSE1070";
097:                                function = "current-grouping-key()";
098:                            }
099:                            StaticError err = new StaticError("The " + function
100:                                    + " function cannot be used in a pattern");
101:                            err.setErrorCode(errorCode);
102:                            throw err;
103:                        }
104:                    }
105:                }
106:
107:                return this ;
108:            }
109:
110:            /**
111:             * Type-check the pattern, performing any type-dependent optimizations.
112:             * @return the optimised Pattern
113:             */
114:
115:            public Pattern analyze(StaticContext env, ItemType contextItemType)
116:                    throws XPathException {
117:
118:                // analyze each component of the pattern
119:                final TypeHierarchy th = env.getNamePool().getTypeHierarchy();
120:                if (parentPattern != null) {
121:                    parentPattern = parentPattern.analyze(env, contextItemType);
122:                    // Check that this step in the pattern makes sense in the context of the parent step
123:                    AxisExpression step;
124:                    if (nodeTest.getPrimitiveType() == Type.ATTRIBUTE) {
125:                        step = new AxisExpression(Axis.ATTRIBUTE, nodeTest);
126:                    } else {
127:                        step = new AxisExpression(Axis.CHILD, nodeTest);
128:                    }
129:                    step.setLocationId(env.getLocationMap().allocateLocationId(
130:                            env.getSystemId(), getLineNumber()));
131:                    step.setParentExpression(this );
132:                    Expression exp = step.typeCheck(env, parentPattern
133:                            .getNodeTest());
134:                    refinedNodeTest = (NodeTest) exp.getItemType(th);
135:                } else if (ancestorPattern != null) {
136:                    ancestorPattern = ancestorPattern.analyze(env,
137:                            contextItemType);
138:                }
139:
140:                if (filters != null) {
141:                    for (int i = numberOfFilters - 1; i >= 0; i--) {
142:                        Expression filter = filters[i].typeCheck(env,
143:                                getNodeTest());
144:                        // System.err.println("Filter after analyze:");filter.display(10);
145:                        filters[i] = filter;
146:                        // if the last filter is constant true, remove it
147:                        if ((filter instanceof  BooleanValue)
148:                                && ((BooleanValue) filter).getBooleanValue()) {
149:                            if (i == numberOfFilters - 1) {
150:                                numberOfFilters--;
151:                            } // otherwise don't bother doing anything with it.
152:                        }
153:
154:                        // patterns are used outside XSLT, for internally-generated key definitions;
155:                        // but in this case they never contain variable references or calls on current(). So we only need to
156:                        // allocate slots in the XSLT case
157:                        if (env instanceof  ExpressionContext) {
158:                            ((ExpressionContext) env).getStyleElement()
159:                                    .allocateSlots(filter);
160:                            filters[i] = filter;
161:                        }
162:                    }
163:                }
164:
165:                // see if it's an element pattern with a single positional predicate of [1]
166:
167:                if (nodeTest.getPrimitiveType() == Type.ELEMENT
168:                        && numberOfFilters == 1) {
169:                    if (((filters[0] instanceof  IntegerValue) && ((IntegerValue) filters[0])
170:                            .longValue() == 1)
171:                            || ((filters[0] instanceof  PositionRange) && ((PositionRange) filters[0])
172:                                    .isFirstPositionOnly())) {
173:                        firstElementPattern = true;
174:                        specialFilter = true;
175:                        numberOfFilters = 0;
176:                        filters = null;
177:                    }
178:                }
179:
180:                // see if it's an element pattern with a single positional predicate
181:                // of [position()=last()]
182:
183:                if (nodeTest.getPrimitiveType() == Type.ELEMENT
184:                        && numberOfFilters == 1
185:                        && filters[0] instanceof  IsLastExpression
186:                        && ((IsLastExpression) filters[0]).getCondition()) {
187:                    lastElementPattern = true;
188:                    specialFilter = true;
189:                    numberOfFilters = 0;
190:                    filters = null;
191:                }
192:
193:                if (isPositional(th)) {
194:                    equivalentExpr = makeEquivalentExpression(env);
195:                    equivalentExpr = equivalentExpr.typeCheck(env,
196:                            contextItemType);
197:                    // the rewritten expression may use additional variables; must ensure there are enough slots for these
198:                    // (see test match55)
199:                    ((ExpressionContext) env).getStyleElement().allocateSlots(
200:                            equivalentExpr);
201:                    specialFilter = true;
202:                }
203:
204:                return this ;
205:
206:                // TODO:PERF: identify subexpressions within a pattern predicate that could be promoted
207:                // In the case of match patterns in template rules, these would have to become global variables.
208:            }
209:
210:            /**
211:             * Get the dependencies of the pattern. The only possible dependency for a pattern is
212:             * on local variables. This is analyzed in those patterns where local variables may appear.
213:             */
214:
215:            public int getDependencies() {
216:                int dependencies = 0;
217:                if (parentPattern != null) {
218:                    dependencies |= parentPattern.getDependencies();
219:                }
220:                if (ancestorPattern != null) {
221:                    dependencies |= ancestorPattern.getDependencies();
222:                }
223:                for (int i = 0; i < numberOfFilters; i++) {
224:                    dependencies |= filters[i].getDependencies();
225:                }
226:                // the only dependency that's interesting is a dependency on local variables
227:                dependencies &= StaticProperty.DEPENDS_ON_LOCAL_VARIABLES;
228:                return dependencies;
229:            }
230:
231:            /**
232:             * Iterate over the subexpressions within this pattern
233:             */
234:
235:            public Iterator iterateSubExpressions() {
236:                Iterator iter;
237:                if (numberOfFilters == 0) {
238:                    iter = Collections.EMPTY_LIST.iterator();
239:                } else {
240:                    iter = Arrays.asList(filters).subList(0, numberOfFilters)
241:                            .iterator();
242:                }
243:                if (variableBinding != null) {
244:                    Iterator[] pair = { iter, new MonoIterator(variableBinding) };
245:                    iter = new MultiIterator(pair);
246:                }
247:                if (parentPattern != null) {
248:                    Iterator[] pair = { iter,
249:                            parentPattern.iterateSubExpressions() };
250:                    iter = new MultiIterator(pair);
251:                }
252:                if (ancestorPattern != null) {
253:                    Iterator[] pair = { iter,
254:                            ancestorPattern.iterateSubExpressions() };
255:                    iter = new MultiIterator(pair);
256:                }
257:                return iter;
258:            }
259:
260:            /**
261:             * Offer promotion for subexpressions within this pattern. The offer will be accepted if the subexpression
262:             * is not dependent on the factors (e.g. the context item) identified in the PromotionOffer.
263:             * By default the offer is not accepted - this is appropriate in the case of simple expressions
264:             * such as constant values and variable references where promotion would give no performance
265:             * advantage. This method is always called at compile time.
266:             * <p/>
267:             * <p>Unlike the corresponding method on {@link net.sf.saxon.expr.Expression}, this method does not return anything:
268:             * it can make internal changes to the pattern, but cannot return a different pattern. Only certain
269:             * kinds of promotion are applicable within a pattern: specifically, promotions affecting local
270:             * variable references within the pattern.
271:             *
272:             * @param offer details of the offer, for example the offer to move
273:             *              expressions that don't depend on the context to an outer level in
274:             *              the containing expression
275:             * @throws net.sf.saxon.trans.XPathException
276:             *          if any error is detected
277:             */
278:
279:            public void promote(PromotionOffer offer) throws XPathException {
280:
281:                if (parentPattern != null) {
282:                    parentPattern.promote(offer);
283:                }
284:                if (ancestorPattern != null) {
285:                    ancestorPattern.promote(offer);
286:                }
287:                for (int i = 0; i < numberOfFilters; i++) {
288:                    filters[i] = filters[i].promote(offer);
289:                }
290:            }
291:
292:            /**
293:             * For a positional pattern, make an equivalent nodeset expression to evaluate the filters
294:             */
295:
296:            private ComputedExpression makeEquivalentExpression(
297:                    StaticContext env) throws XPathException {
298:                byte axis = (nodeTest.getPrimitiveType() == Type.ATTRIBUTE ? Axis.ATTRIBUTE
299:                        : Axis.CHILD);
300:                ComputedExpression step = new AxisExpression(axis, nodeTest);
301:                for (int n = 0; n < numberOfFilters; n++) {
302:                    step = new FilterExpression(step, filters[n], env);
303:                }
304:                PathExpression path = new PathExpression(
305:                        new ParentNodeExpression(), step);
306:                path.setParentExpression(this );
307:                return path;
308:                // Note, the resulting expression is not required to deliver results in document order
309:            }
310:
311:            /**
312:             * Determine whether the pattern matches a given node.
313:             * @param node the node to be tested
314:             * @return true if the pattern matches, else false
315:             */
316:
317:            public boolean matches(NodeInfo node, XPathContext context)
318:                    throws XPathException {
319:                if (variableBinding != null) {
320:                    variableBinding.evaluateItem(context);
321:                }
322:                return internalMatches(node, context);
323:                // matches() and internalMatches() differ in the way they handled the current() function.
324:                // The variable holding the value of current() is initialized on entry to the top-level
325:                // LocationPathPattern, but not on entry to its subordinate patterns.
326:            }
327:
328:            /**
329:             * Test whether the pattern matches, but without changing the current() node
330:             */
331:
332:            protected boolean internalMatches(NodeInfo node,
333:                    XPathContext context) throws XPathException {
334:                // System.err.println("Matching node type and fingerprint");
335:                if (!nodeTest.matches(node)) {
336:                    return false;
337:                }
338:                if (parentPattern != null) {
339:                    //System.err.println("Testing parent pattern " + parentPattern + "(" + parentPattern.getClass() + ")");
340:                    NodeInfo par = node.getParent();
341:                    if (par == null)
342:                        return false;
343:                    if (!parentPattern.internalMatches(par, context)) {
344:                        return false;
345:                    }
346:                }
347:
348:                if (ancestorPattern != null) {
349:                    NodeInfo anc = node.getParent();
350:                    while (true) {
351:                        if (anc == null)
352:                            return false;
353:                        if (ancestorPattern.internalMatches(anc, context))
354:                            break;
355:                        anc = anc.getParent();
356:                    }
357:                }
358:
359:                if (specialFilter) {
360:                    if (firstElementPattern) {
361:                        SequenceIterator iter = node.iterateAxis(
362:                                Axis.PRECEDING_SIBLING, nodeTest);
363:                        return iter.next() == null;
364:                    }
365:
366:                    if (lastElementPattern) {
367:                        SequenceIterator iter = node.iterateAxis(
368:                                Axis.FOLLOWING_SIBLING, nodeTest);
369:                        return iter.next() == null;
370:                    }
371:
372:                    if (equivalentExpr != null) {
373:
374:                        // for a positional pattern, we do it the hard way: test whether the
375:                        // node is a member of the nodeset obtained by evaluating the
376:                        // equivalent expression
377:
378:                        // System.err.println("Testing positional pattern against node " + node.generateId());
379:                        XPathContext c2 = context.newMinorContext();
380:                        c2.setOriginatingConstructType(Location.PATTERN);
381:                        AxisIterator single = SingletonIterator
382:                                .makeIterator(node);
383:                        single.next();
384:                        c2.setCurrentIterator(single);
385:                        try {
386:                            SequenceIterator nsv = equivalentExpr.iterate(c2);
387:                            while (true) {
388:                                NodeInfo n = (NodeInfo) nsv.next();
389:                                if (n == null) {
390:                                    return false;
391:                                }
392:                                if (n.isSameNodeInfo(node)) {
393:                                    return true;
394:                                }
395:                            }
396:                        } catch (DynamicError e) {
397:                            DynamicError err = new DynamicError(
398:                                    "An error occurred matching pattern {"
399:                                            + toString() + "}: ", e);
400:                            err.setXPathContext(c2);
401:                            err.setErrorCode(e.getErrorCodeLocalPart());
402:                            err.setLocator(this );
403:                            c2.getController().recoverableError(err);
404:                            return false;
405:                        }
406:                    }
407:                }
408:
409:                if (filters != null) {
410:                    XPathContext c2 = context.newMinorContext();
411:                    c2.setOriginatingConstructType(Location.PATTERN);
412:                    AxisIterator iter = SingletonIterator.makeIterator(node);
413:                    iter.next();
414:                    c2.setCurrentIterator(iter);
415:                    // it's a non-positional filter, so we can handle each node separately
416:
417:                    for (int i = 0; i < numberOfFilters; i++) {
418:                        try {
419:                            if (!filters[i].effectiveBooleanValue(c2)) {
420:                                return false;
421:                            }
422:                        } catch (DynamicError e) {
423:                            DynamicError err = new DynamicError(
424:                                    "An error occurred matching pattern {"
425:                                            + toString() + "}: ", e);
426:                            err.setXPathContext(c2);
427:                            err.setErrorCode(e.getErrorCodeLocalPart());
428:                            err.setLocator(this );
429:                            c2.getController().recoverableError(err);
430:                            return false;
431:                        }
432:                    }
433:                }
434:
435:                return true;
436:            }
437:
438:            /**
439:             * Determine the types of nodes to which this pattern applies. Used for optimisation.
440:             * For patterns that match nodes of several types, return Node.NODE
441:             * @return the type of node matched by this pattern. e.g. Node.ELEMENT or Node.TEXT
442:             */
443:
444:            public int getNodeKind() {
445:                return nodeTest.getPrimitiveType();
446:            }
447:
448:            /**
449:             * Determine the fingerprint of nodes to which this pattern applies.
450:             * Used for optimisation.
451:             * @return the fingerprint of nodes matched by this pattern.
452:             */
453:
454:            public int getFingerprint() {
455:                return nodeTest.getFingerprint();
456:            }
457:
458:            /**
459:             * Get a NodeTest that all the nodes matching this pattern must satisfy
460:             */
461:
462:            public NodeTest getNodeTest() {
463:                if (refinedNodeTest != null) {
464:                    return refinedNodeTest;
465:                } else {
466:                    return nodeTest;
467:                }
468:            }
469:
470:            /**
471:             * Determine if the pattern uses positional filters
472:             * @return true if there is a numeric filter in the pattern, or one that uses the position()
473:             * or last() functions
474:             */
475:
476:            private boolean isPositional(TypeHierarchy th) {
477:                if (filters == null)
478:                    return false;
479:                for (int i = 0; i < numberOfFilters; i++) {
480:                    int type = filters[i].getItemType(th).getPrimitiveType();
481:                    if (type == Type.DOUBLE || type == Type.DECIMAL
482:                            || type == Type.INTEGER || type == Type.FLOAT
483:                            || type == Type.ANY_ATOMIC)
484:                        return true;
485:                    if ((filters[i].getDependencies() & (StaticProperty.DEPENDS_ON_POSITION | StaticProperty.DEPENDS_ON_LAST)) != 0)
486:                        return true;
487:                }
488:                return false;
489:            }
490:
491:            /**
492:             * If the pattern contains any calls on current(), this method is called to modify such calls
493:             * to become variable references to a variable declared in a specially-allocated local variable
494:             * @param let the expression that assigns the local variable. This returns a dummy result, and is executed
495:             * just before evaluating the pattern, to get the value of the context item into the variable.
496:             * @param offer A PromotionOffer used to process the expressions and change the call on current() into
497:             * a variable reference
498:             * @throws XPathException
499:             */
500:
501:            public void resolveCurrent(LetExpression let, PromotionOffer offer)
502:                    throws XPathException {
503:                for (int i = 0; i < numberOfFilters; i++) {
504:                    filters[i] = filters[i].promote(offer);
505:                }
506:                if (parentPattern instanceof  LocationPathPattern) {
507:                    ((LocationPathPattern) parentPattern).resolveCurrent(let,
508:                            offer);
509:                }
510:                if (ancestorPattern instanceof  LocationPathPattern) {
511:                    ((LocationPathPattern) ancestorPattern).resolveCurrent(let,
512:                            offer);
513:                }
514:                variableBinding = let;
515:            }
516:        }
517:
518:        //
519:        // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
520:        // you may not use this file except in compliance with the License. You may obtain a copy of the
521:        // License at http://www.mozilla.org/MPL/
522:        //
523:        // Software distributed under the License is distributed on an "AS IS" basis,
524:        // WITHOUT WARRANTY OF ANY KIND, either express or implied.
525:        // See the License for the specific language governing rights and limitations under the License.
526:        //
527:        // The Original Code is: all this file.
528:        //
529:        // The Initial Developer of the Original Code is Michael H. Kay.
530:        //
531:        // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
532:        //
533:        // Contributor(s): none.
534:        //
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