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

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


001:        package net.sf.saxon.expr;
002:
003:        import net.sf.saxon.instruct.InstructionDetails;
004:        import net.sf.saxon.instruct.UserFunction;
005:        import net.sf.saxon.om.*;
006:        import net.sf.saxon.trace.InstructionInfo;
007:        import net.sf.saxon.trace.InstructionInfoProvider;
008:        import net.sf.saxon.trace.Location;
009:        import net.sf.saxon.trans.DynamicError;
010:        import net.sf.saxon.trans.XPathException;
011:        import net.sf.saxon.type.AnyItemType;
012:        import net.sf.saxon.type.ItemType;
013:        import net.sf.saxon.type.TypeHierarchy;
014:        import net.sf.saxon.value.*;
015:
016:        import java.io.PrintStream;
017:
018:        /**
019:         * This class represents a call to a function defined in the stylesheet or query.
020:         * It is used for all user-defined functions in XQuery, and for a limited class of
021:         * user-defined functions in XSLT: those that can be reduced to the evaluation
022:         * of a single expression.
023:         */
024:
025:        public class UserFunctionCall extends FunctionCall implements 
026:                InstructionInfoProvider {
027:
028:            private SequenceType staticType;
029:            private UserFunction function;
030:            private boolean tailRecursive = false;
031:            private boolean confirmed = false;
032:
033:            // A functionCall is confirmed if the function being called has been located. Generally in this
034:            // case the value of 'function' will be non-null; but in XSLT it is possible to look-ahead to confirm
035:            // a function binding before the relevant function is actually compiled.
036:
037:            public UserFunctionCall() {
038:            }
039:
040:            /**
041:             * Set the static type
042:             */
043:
044:            public void setStaticType(SequenceType type) {
045:                staticType = type;
046:            }
047:
048:            /**
049:             * Create the reference to the function to be called, and validate for consistency
050:             */
051:
052:            public void setFunction(UserFunction compiledFunction,
053:                    StaticContext env) throws XPathException {
054:                function = compiledFunction;
055:                confirmed = true;
056:            }
057:
058:            /**
059:             * Check the function call against the declared function signature
060:             */
061:
062:            public void checkFunctionCall(UserFunction compiledFunction,
063:                    StaticContext env) throws XPathException {
064:                int n = compiledFunction.getNumberOfArguments();
065:                for (int i = 0; i < n; i++) {
066:                    RoleLocator role = new RoleLocator(
067:                            RoleLocator.FUNCTION,
068:                            new Integer(compiledFunction.getFunctionNameCode()),
069:                            i, env.getNamePool());
070:                    role.setSourceLocator(this );
071:                    argument[i] = TypeChecker.staticTypeCheck(argument[i],
072:                            compiledFunction.getArgumentType(i), false, role,
073:                            env);
074:                }
075:            }
076:
077:            /**
078:             * Get the function that is being called by this function call
079:             */
080:
081:            public UserFunction getFunction() {
082:                return function;
083:            }
084:
085:            /**
086:             * Set this function as confirmed (the function being called is known to exist) or not
087:             */
088:
089:            public void setConfirmed(boolean conf) {
090:                confirmed = conf;
091:            }
092:
093:            /**
094:             * Determine whether this function call is confirmed
095:             */
096:
097:            public boolean isConfirmed() {
098:                return confirmed;
099:            }
100:
101:            /**
102:             * Get the arguments (the expressions supplied in the function call)
103:             */
104:
105:            public Expression[] getArguments() {
106:                return argument;
107:            }
108:
109:            /**
110:             * Method called during the type checking phase
111:             */
112:
113:            public void checkArguments(StaticContext env) throws XPathException {
114:                // these checks are now done in setFunction(), at the time when the function
115:                // call is bound to an actual function
116:            }
117:
118:            /**
119:             * Pre-evaluate a function at compile time. This version of the method suppresses
120:             * early evaluation by doing nothing.
121:             */
122:
123:            public Expression preEvaluate(StaticContext env) {
124:                return this ;
125:            }
126:
127:            /**
128:             * Determine the data type of the expression, if possible
129:             * @return Type.ITEM (meaning not known in advance)
130:             * @param th
131:             */
132:
133:            public ItemType getItemType(TypeHierarchy th) {
134:                if (staticType == null) {
135:                    // the actual type is not known yet, so we return an approximation
136:                    return AnyItemType.getInstance();
137:                } else {
138:                    return staticType.getPrimaryType();
139:                }
140:            }
141:
142:            public int getIntrinsicDependencies() {
143:                return StaticProperty.DEPENDS_ON_USER_FUNCTIONS;
144:            }
145:
146:            /**
147:             * Determine the cardinality of the result
148:             */
149:
150:            public int computeCardinality() {
151:                if (staticType == null) {
152:                    // the actual type is not known yet, so we return an approximation
153:                    return StaticProperty.ALLOWS_ZERO_OR_MORE;
154:                } else {
155:                    return staticType.getCardinality();
156:                }
157:            }
158:
159:            /**
160:             * Simplify the function call
161:             */
162:
163:            public Expression simplify(StaticContext env) throws XPathException {
164:                for (int i = 0; i < argument.length; i++) {
165:                    argument[i] = argument[i].simplify(env);
166:                }
167:                return this ;
168:            }
169:
170:            /**
171:             * Mark tail-recursive calls on stylesheet functions. For most expressions, this does nothing.
172:             */
173:
174:            public boolean markTailFunctionCalls() {
175:                tailRecursive = true;
176:                return true;
177:            }
178:
179:            // TODO: attempt to establish whether the function is capable of creating new nodes. This
180:            // enables non-creative functions to be moved out of loops. The problem is how to achieve this
181:            // without looping in the case of recursive functions. A simple solution might be to go only
182:            // one level deep: if the body of a function is known (without analysing function calls) to be
183:            // non-creative, then all calls on that function can be marked as non-creative. Note also that
184:            // a function is creative if one of its arguments is creative and the result of the function
185:            // depends on the identity of that argument.
186:
187:            /**
188:             * Call the function, returning the value as an item. This method will be used
189:             * only when the cardinality is zero or one. If the function is tail recursive,
190:             * it returns an Object representing the arguments to the next (recursive) call
191:             */
192:
193:            public Item evaluateItem(XPathContext c) throws XPathException {
194:                ValueRepresentation val = callFunction(c);
195:                if (val instanceof  Item) {
196:                    return (Item) val;
197:                } else {
198:                    return Value.getIterator(val).next();
199:                }
200:            }
201:
202:            /**
203:             * Call the function, returning an iterator over the results. (But if the function is
204:             * tail recursive, it returns an iterator over the arguments of the recursive call)
205:             */
206:
207:            public SequenceIterator iterate(XPathContext c)
208:                    throws XPathException {
209:                ValueRepresentation result = callFunction(c);
210:                if (result instanceof  FunctionCallPackage) {
211:                    return SingletonIterator
212:                            .makeIterator(((FunctionCallPackage) result));
213:                }
214:                return Value.getIterator(result);
215:            }
216:
217:            /**
218:             * This is the method that actually does the function call
219:             * @param c the dynamic context
220:             * @return the result of the function
221:             * @throws XPathException if dynamic errors occur
222:             */
223:            private ValueRepresentation callFunction(XPathContext c)
224:                    throws XPathException {
225:                int numArgs = argument.length;
226:
227:                ValueRepresentation[] actualArgs = new ValueRepresentation[numArgs];
228:                for (int i = 0; i < numArgs; i++) {
229:                    // Decide what form of lazy evaluation to use based on the number of references to the argument
230:                    int refs = function.getParameterDefinitions()[i]
231:                            .getReferenceCount();
232:                    if (argument[i] instanceof  Value) {
233:                        actualArgs[i] = (Value) argument[i];
234:                    } else {
235:                        if (refs == 0) {
236:                            // the argument is never referenced, so don't evaluate it
237:                            actualArgs[i] = EmptySequence.getInstance();
238:                        } else if ((argument[i].getDependencies() & StaticProperty.DEPENDS_ON_USER_FUNCTIONS) != 0) {
239:                            // if the argument contains a call to a user-defined function, then it might be a recursive call.
240:                            // It's better to evaluate it now, rather than waiting until we are on a new stack frame, as
241:                            // that can blow the stack if done repeatedly.
242:                            actualArgs[i] = ExpressionTool.eagerEvaluate(
243:                                    argument[i], c);
244:                        } else {
245:                            actualArgs[i] = ExpressionTool.lazyEvaluate(
246:                                    argument[i], c, refs);
247:                        }
248:                    }
249:                    // If the argument has come in as a (non-memo) closure but there are multiple references to it,
250:                    // then we materialize it in memory now. This shouldn't really happen but it does (tour.xq)
251:                    if (refs > 1 && actualArgs[i] instanceof  Closure
252:                            && !(actualArgs[i] instanceof  MemoClosure)) {
253:                        actualArgs[i] = ((Closure) actualArgs[i]).reduce();
254:                    }
255:                }
256:
257:                if (tailRecursive) {
258:                    return new FunctionCallPackage(function, actualArgs, c);
259:                }
260:
261:                XPathContextMajor c2 = c.newCleanContext();
262:                c2.setOrigin(this );
263:                try {
264:                    return function.call(actualArgs, c2, true);
265:                } catch (StackOverflowError err) {
266:                    throw new DynamicError(
267:                            "Too many nested function calls. May be due to infinite recursion.",
268:                            this );
269:                } catch (NullPointerException err) {
270:                    throw new NullPointerException("Unbound function call "
271:                            + c2.getConfiguration().getNamePool()
272:                                    .getDisplayName(getFunctionNameCode()));
273:                }
274:            }
275:
276:            /**
277:             * Call the function dynamically. For this to be possible, the static arguments of the function call
278:             * must have been set up as SuppliedParameterReference objects. The actual arguments are placed on the
279:             * callee's stack, and the type conversion takes place "in situ".
280:             */
281:
282:            public ValueRepresentation dynamicCall(
283:                    ValueRepresentation[] suppliedArguments,
284:                    XPathContext context) throws XPathException {
285:                ValueRepresentation[] convertedArgs = new ValueRepresentation[suppliedArguments.length];
286:                XPathContextMajor c2 = context.newCleanContext();
287:                c2.setOrigin(this );
288:                c2.setCaller(context);
289:                c2.openStackFrame(suppliedArguments.length);
290:                for (int i = 0; i < suppliedArguments.length; i++) {
291:                    c2.setLocalVariable(i, suppliedArguments[i]);
292:                    convertedArgs[i] = ExpressionTool.lazyEvaluate(argument[i],
293:                            c2, 10);
294:                }
295:                XPathContextMajor c3 = c2.newCleanContext();
296:                c3.setOrigin(this );
297:                return function.call(convertedArgs, c3, true);
298:            }
299:
300:            public void display(int level, NamePool pool, PrintStream out) {
301:                out.println(ExpressionTool.indent(level) + "function "
302:                        + getDisplayName(pool)
303:                        + (tailRecursive ? " (tail call)" : ""));
304:                for (int a = 0; a < argument.length; a++) {
305:                    argument[a].display(level + 1, pool, out);
306:                }
307:            }
308:
309:            /**
310:             * Get diagnostic information about this expression
311:             */
312:
313:            public InstructionInfo getInstructionInfo() {
314:                InstructionDetails details = new InstructionDetails();
315:                details.setConstructType(Location.FUNCTION_CALL);
316:                details.setLineNumber(getLineNumber());
317:                details.setSystemId(getSystemId());
318:                details.setObjectNameCode(getFunctionNameCode());
319:                details.setProperty("expression", this );
320:                details.setProperty("target", function);
321:                return details;
322:            }
323:
324:            /**
325:             * Inner class used to wrap up the set of actual arguments to a tail-recursive call of
326:             * the containing function. This argument package is passed back to the calling code
327:             * in place of a function result; the caller then loops to re-invoke the function
328:             * with these arguments, avoiding the creation of an additional stack frame.
329:             */
330:
331:            public class FunctionCallPackage extends ObjectValue {
332:
333:                private UserFunction function;
334:                private ValueRepresentation[] actualArgs;
335:                private XPathContext evaluationContext;
336:
337:                public FunctionCallPackage(UserFunction function,
338:                        ValueRepresentation[] actualArgs, XPathContext c) {
339:                    super (function);
340:                    this .function = function;
341:                    this .actualArgs = actualArgs;
342:                    this .evaluationContext = c;
343:                }
344:
345:                /**
346:                 * Determine the item type of the expression
347:                 * @param th
348:                 */
349:
350:                public ItemType getItemType(TypeHierarchy th) {
351:                    return UserFunctionCall.this .getItemType(th);
352:                }
353:
354:                public ValueRepresentation call() throws XPathException {
355:                    XPathContextMajor c2 = evaluationContext.newCleanContext();
356:                    c2.setOrigin(UserFunctionCall.this );
357:                    return function.call(actualArgs, c2, false);
358:                }
359:
360:                public SequenceIterator iterateResults(XPathContext context)
361:                        throws XPathException {
362:                    ValueRepresentation result = call();
363:                    return new MappingIterator(Value.getIterator(result),
364:                            Flattener.THE_INSTANCE, context);
365:                }
366:
367:                //        public ValueRepresentation appendTo(SequenceReceiver out) throws XPathException {
368:                //            // This method has been combined with the only method that called it (Instruction.appendItem())
369:                //            ValueRepresentation v = call();
370:                //            SequenceIterator fv = Value.getIterator(v);
371:                //            while (true) {
372:                //                Item fvit = fv.next();
373:                //                if (fvit == null) return null;
374:                //                if (fvit instanceof UserFunctionCall.FunctionCallPackage) {
375:                //                    return (Value)fvit;
376:                //                } else {
377:                //                    out.append(fvit, locationId, NodeInfo.ALL_NAMESPACES);
378:                //                }
379:                //            }
380:                //        }
381:
382:                /**
383:                 * Reduce a value to its simplest form. If the value is a closure or some other form of deferred value
384:                 * such as a FunctionCallPackage, then it is reduced to a SequenceExtent. If it is a SequenceExtent containing
385:                 * a single item, then it is reduced to that item. One consequence that is exploited by class FilterExpression
386:                 * is that if the value is a singleton numeric value, then the result will be an instance of NumericValue
387:                 */
388:
389:                public Value reduce() throws XPathException {
390:                    return new SequenceExtent(iterateResults(null)).reduce();
391:                }
392:
393:                /**
394:                 * Get the primitive value (the value in the value space). This returns an
395:                 * AtomicValue of a class that would be used to represent the primitive value.
396:                 * In effect this means that for built-in types, it returns the value itself,
397:                 * but for user-defined type, it returns the primitive value minus the type
398:                 * annotation. Note that getItemType() when applied to the result of this
399:                 * function does not not necessarily return a primitive type: for example, this
400:                 * function may return a value of type xdt:dayTimeDuration, which is not a
401:                 * primitive type as defined by {@link net.sf.saxon.type.Type#isPrimitiveType(int)}
402:                 */
403:
404:                public AtomicValue getPrimitiveValue() {
405:                    try {
406:                        return ((AtomicValue) reduce()).getPrimitiveValue();
407:                    } catch (XPathException e) {
408:                        throw new RuntimeException(e);
409:                    }
410:                }
411:            }
412:
413:            /**
414:             * Mapping function that converts a sequence possibly containing embedded FunctionCallPackage items into
415:             * one in which any such items are fully expanded
416:             */
417:
418:            private static class Flattener implements  MappingFunction {
419:
420:                public static final Flattener THE_INSTANCE = new Flattener();
421:
422:                private Flattener() {
423:                }
424:
425:                /**
426:                 * Map one item to a sequence.
427:                 *
428:                 * @param item    The item to be mapped.
429:                 *                If context is supplied, this must be the same as context.currentItem().
430:                 * @param context The processing context. Some mapping functions use this because they require
431:                 *                context information. Some mapping functions modify the context by maintaining the context item
432:                 *                and position. In other cases, the context may be null.
433:                 * @return either (a) a SequenceIterator over the sequence of items that the supplied input
434:                 *         item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty
435:                 *         sequence.
436:                 */
437:
438:                public Object map(Item item, XPathContext context)
439:                        throws XPathException {
440:                    if (item instanceof  FunctionCallPackage) {
441:                        return (((FunctionCallPackage) item)
442:                                .iterateResults(context));
443:                    } else {
444:                        return item;
445:                    }
446:                }
447:
448:            }
449:
450:        }
451:
452:        //
453:        // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
454:        // you may not use this file except in compliance with the License. You may obtain a copy of the
455:        // License at http://www.mozilla.org/MPL/
456:        //
457:        // Software distributed under the License is distributed on an "AS IS" basis,
458:        // WITHOUT WARRANTY OF ANY KIND, either express or implied.
459:        // See the License for the specific language governing rights and limitations under the License.
460:        //
461:        // The Original Code is: all this file.
462:        //
463:        // The Initial Developer of the Original Code is Michael H. Kay.
464:        //
465:        // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
466:        //
467:        // Contributor(s): none.
468:        //
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