Source Code Cross Referenced for SimpleMappingExpression.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.om.*;
004:        import net.sf.saxon.sort.DocumentOrderIterator;
005:        import net.sf.saxon.sort.GlobalOrderComparer;
006:        import net.sf.saxon.trace.Location;
007:        import net.sf.saxon.trans.DynamicError;
008:        import net.sf.saxon.trans.XPathException;
009:        import net.sf.saxon.type.ItemType;
010:        import net.sf.saxon.type.TypeHierarchy;
011:        import net.sf.saxon.value.AtomicValue;
012:        import net.sf.saxon.value.Cardinality;
013:
014:        import java.io.PrintStream;
015:        import java.util.Iterator;
016:
017:        /**
018:         * A simple mapping expression is an expression A/B where B has a static type that is an atomic type.
019:         * For example, * / name().
020:         */
021:
022:        public final class SimpleMappingExpression extends ComputedExpression
023:                implements  MappingFunction {
024:
025:            private Expression start;
026:            private Expression step;
027:            private boolean isHybrid;
028:
029:            /**
030:             * Constructor
031:             * @param start A node-set expression denoting the absolute or relative set of nodes from which the
032:             * navigation path should start.
033:             * @param step The step to be followed from each node in the start expression to yield a new
034:             * node-set
035:             * @param isHybrid if true, indicates that we don't know statically whether the step expression will
036:             * return nodes or atomic values. If false, we know it will return atomic values.
037:             */
038:
039:            public SimpleMappingExpression(Expression start, Expression step,
040:                    boolean isHybrid) {
041:                this .start = start;
042:                this .step = step;
043:                this .isHybrid = isHybrid;
044:                adoptChildExpression(start);
045:                adoptChildExpression(step);
046:
047:            }
048:
049:            /**
050:             * Get the start expression (the left-hand operand)
051:             */
052:
053:            public Expression getStartExpression() {
054:                return start;
055:            }
056:
057:            /**
058:             * Get the step expression (the right-hand operand)
059:             */
060:
061:            public Expression getStepExpression() {
062:                return step;
063:            }
064:
065:            /**
066:             * Determine the data type of the items returned by this exprssion
067:             * @return the type of the step
068:             * @param th
069:             */
070:
071:            public final ItemType getItemType(TypeHierarchy th) {
072:                return step.getItemType(th);
073:            }
074:
075:            /**
076:             * Simplify an expression
077:             * @return the simplified expression
078:             */
079:
080:            public Expression simplify(StaticContext env) {
081:                // We rely on the fact that the operands were already simplified
082:                return this ;
083:            }
084:
085:            /**
086:             * Type-check the expression
087:             */
088:
089:            public Expression typeCheck(StaticContext env,
090:                    ItemType contextItemType) {
091:                // rely on the fact that the original path expression has already been type-checked
092:                return this ;
093:            }
094:
095:            public Expression optimize(Optimizer opt, StaticContext env,
096:                    ItemType contextItemType) throws XPathException {
097:                return this ;
098:            }
099:
100:            /**
101:             * Promote this expression if possible
102:             */
103:
104:            public Expression promote(PromotionOffer offer)
105:                    throws XPathException {
106:                Expression exp = offer.accept(this );
107:                if (exp != null) {
108:                    return exp;
109:                } else {
110:                    start = doPromotion(start, offer);
111:                    if (offer.action == PromotionOffer.INLINE_VARIABLE_REFERENCES
112:                            || offer.action == PromotionOffer.REPLACE_CURRENT) {
113:                        // Don't pass on other requests. We could pass them on, but only after augmenting
114:                        // them to say we are interested in subexpressions that don't depend on either the
115:                        // outer context or the inner context.
116:                        step = doPromotion(step, offer);
117:                    }
118:                    resetStaticProperties();
119:                    return this ;
120:                }
121:            }
122:
123:            /**
124:             * Get the immediate subexpressions of this expression
125:             */
126:
127:            public Iterator iterateSubExpressions() {
128:                return new PairIterator(start, step);
129:            }
130:
131:            /**
132:             * Determine which aspects of the context the expression depends on. The result is
133:             * a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and
134:             * XPathContext.CURRENT_NODE
135:             */
136:
137:            public int computeDependencies() {
138:                return start.getDependencies() |
139:                // not all dependencies in the step matter, because the context node, etc,
140:                        // are not those of the outer expression
141:                        (step.getDependencies() & StaticProperty.DEPENDS_ON_XSLT_CONTEXT);
142:            }
143:
144:            /**
145:             * Get the static properties of this expression (other than its type). The result is
146:             * bit-signficant. These properties are used for optimizations. In general, if
147:             * property bit is set, it is true, but if it is unset, the value is unknown.
148:             */
149:
150:            public int computeSpecialProperties() {
151:                int p = super .computeSpecialProperties();
152:                if ((start.getSpecialProperties() & step.getSpecialProperties() & StaticProperty.NON_CREATIVE) != 0) {
153:                    p |= StaticProperty.NON_CREATIVE;
154:                }
155:                return p;
156:            }
157:
158:            /**
159:             * Determine the static cardinality of the expression
160:             */
161:
162:            public int computeCardinality() {
163:                int c1 = start.getCardinality();
164:                int c2 = step.getCardinality();
165:                return Cardinality.multiply(c1, c2);
166:            }
167:
168:            /**
169:             * Is this expression the same as another expression?
170:             */
171:
172:            public boolean equals(Object other) {
173:                if (!(other instanceof  SimpleMappingExpression)) {
174:                    return false;
175:                }
176:                SimpleMappingExpression p = (SimpleMappingExpression) other;
177:                return (start.equals(p.start) && step.equals(p.step));
178:            }
179:
180:            /**
181:             * get HashCode for comparing two expressions
182:             */
183:
184:            public int hashCode() {
185:                return "SimpleMappingExpression".hashCode() + start.hashCode()
186:                        + step.hashCode();
187:            }
188:
189:            /**
190:             * Iterate the path-expression in a given context
191:             * @param context the evaluation context
192:             */
193:
194:            public SequenceIterator iterate(XPathContext context)
195:                    throws XPathException {
196:
197:                // This class delivers the result of the path expression in unsorted order,
198:                // without removal of duplicates. If sorting and deduplication are needed,
199:                // this is achieved by wrapping the path expression in a DocumentSorter
200:
201:                SequenceIterator result = start.iterate(context);
202:                XPathContext context2 = context.newMinorContext();
203:                context2.setCurrentIterator(result);
204:                context2.setOriginatingConstructType(Location.PATH_EXPRESSION);
205:
206:                result = new MappingIterator(result, this , context2);
207:                if (isHybrid) {
208:                    // This case is rare so we don't worry too much about performance
209:                    // Peek at the first node, and depending on its type, check that all the items
210:                    // are atomic values or that all are nodes.
211:                    Item first = result.next();
212:                    if (first == null) {
213:                        return EmptyIterator.getInstance();
214:                    } else if (first instanceof  AtomicValue) {
215:                        return new MappingIterator(result.getAnother(),
216:                                AtomicValueChecker.theInstance, null);
217:                    } else {
218:                        return new DocumentOrderIterator(new MappingIterator(
219:                                result.getAnother(), NodeChecker.theInstance,
220:                                null), GlobalOrderComparer.getInstance());
221:                    }
222:                } else {
223:                    return result;
224:                }
225:            }
226:
227:            /**
228:             * Mapping function, from a node returned by the start iteration, to a sequence
229:             * returned by the child.
230:             */
231:
232:            public Object map(Item item, XPathContext context)
233:                    throws XPathException {
234:                return step.iterate(context);
235:            }
236:
237:            /**
238:             * Diagnostic print of expression structure
239:             */
240:
241:            public void display(int level, NamePool pool, PrintStream out) {
242:                out.println(ExpressionTool.indent(level) + "map /");
243:                start.display(level + 1, pool, out);
244:                step.display(level + 1, pool, out);
245:            }
246:
247:            private static class AtomicValueChecker implements  MappingFunction {
248:                public static AtomicValueChecker theInstance = new AtomicValueChecker();
249:
250:                public Object map(Item item, XPathContext context)
251:                        throws XPathException {
252:                    if (item instanceof  AtomicValue) {
253:                        return item;
254:                    } else {
255:                        DynamicError err = new DynamicError(
256:                                "Cannot mix nodes and atomic values in the result of a path expression");
257:                        err.setErrorCode("XPTY0018");
258:                        err.setXPathContext(context);
259:                        throw err;
260:                    }
261:                }
262:            }
263:
264:            private static class NodeChecker implements  MappingFunction {
265:                public static NodeChecker theInstance = new NodeChecker();
266:
267:                public Object map(Item item, XPathContext context)
268:                        throws XPathException {
269:                    if (item instanceof  NodeInfo) {
270:                        return item;
271:                    } else {
272:                        DynamicError err = new DynamicError(
273:                                "Cannot mix nodes and atomic values in the result of a path expression");
274:                        err.setErrorCode("XPTY0018");
275:                        err.setXPathContext(context);
276:                        throw err;
277:                    }
278:                }
279:            }
280:        }
281:
282:        //
283:        // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
284:        // you may not use this file except in compliance with the License. You may obtain a copy of the
285:        // License at http://www.mozilla.org/MPL/
286:        //
287:        // Software distributed under the License is distributed on an "AS IS" basis,
288:        // WITHOUT WARRANTY OF ANY KIND, either express or implied.
289:        // See the License for the specific language governing rights and limitations under the License.
290:        //
291:        // The Original Code is: all this file.
292:        //
293:        // The Initial Developer of the Original Code is Michael H. Kay.
294:        //
295:        // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
296:        //
297:        // Contributor(s): none.
298:        //
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