Source Code Cross Referenced for PositionRange.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.Item;
004:        import net.sf.saxon.om.NamePool;
005:        import net.sf.saxon.om.SequenceIterator;
006:        import net.sf.saxon.trans.XPathException;
007:        import net.sf.saxon.type.ItemType;
008:        import net.sf.saxon.type.Type;
009:        import net.sf.saxon.type.TypeHierarchy;
010:        import net.sf.saxon.value.BooleanValue;
011:        import net.sf.saxon.value.NumericValue;
012:        import net.sf.saxon.value.IntegerValue;
013:
014:        import java.io.PrintStream;
015:        import java.util.Iterator;
016:
017:        /**
018:         * PositionRange: a boolean expression that tests whether the position() is
019:         * within a certain range. This expression can occur in any context but it is
020:         * optimized when it appears as a predicate (see FilterIterator)
021:         */
022:
023:        public final class PositionRange extends ComputedExpression {
024:
025:            private Expression minPosition;
026:            private Expression maxPosition; // may be null to indicate an open range
027:
028:            /**
029:             * Create a position range
030:             */
031:
032:            public PositionRange(Expression min, Expression max) {
033:                minPosition = min;
034:                maxPosition = max;
035:                adoptChildExpression(min);
036:                adoptChildExpression(max);
037:            }
038:
039:            /**
040:             * Create a constant position range
041:             */
042:
043:            public PositionRange(int min, int max) {
044:                minPosition = new IntegerValue(min);
045:                if (max == Integer.MAX_VALUE) {
046:                    maxPosition = null;
047:                } else {
048:                    maxPosition = new IntegerValue(max);
049:                }
050:            }
051:
052:            /**
053:             * Simplify an expression
054:             * @return the simplified expression
055:             */
056:
057:            public Expression simplify(StaticContext env) throws XPathException {
058:                minPosition = minPosition.simplify(env);
059:                if (maxPosition != null) {
060:                    maxPosition = maxPosition.simplify(env);
061:                }
062:                return this ;
063:            }
064:
065:            /**
066:             * Type-check the expression
067:             */
068:
069:            public Expression typeCheck(StaticContext env,
070:                    ItemType contextItemType) throws XPathException {
071:                minPosition = minPosition.typeCheck(env, contextItemType);
072:                if (maxPosition != null) {
073:                    maxPosition = maxPosition.typeCheck(env, contextItemType);
074:                }
075:                return this ;
076:            }
077:
078:            /**
079:             * Perform optimisation of an expression and its subexpressions.
080:             * <p/>
081:             * <p>This method is called after all references to functions and variables have been resolved
082:             * to the declaration of the function or variable, and after all type checking has been done.</p>
083:             *
084:             * @param opt             the optimizer in use. This provides access to supporting functions; it also allows
085:             *                        different optimization strategies to be used in different circumstances.
086:             * @param env             the static context of the expression
087:             * @param contextItemType the static type of "." at the point where this expression is invoked.
088:             *                        The parameter is set to null if it is known statically that the context item will be undefined.
089:             *                        If the type of the context item is not known statically, the argument is set to
090:             *                        {@link net.sf.saxon.type.Type#ITEM_TYPE}
091:             * @return the original expression, rewritten if appropriate to optimize execution
092:             * @throws net.sf.saxon.trans.StaticError if an error is discovered during this phase
093:             *                                        (typically a type error)
094:             */
095:
096:            public Expression optimize(Optimizer opt, StaticContext env,
097:                    ItemType contextItemType) throws XPathException {
098:                minPosition = minPosition.optimize(opt, env, contextItemType);
099:                if (maxPosition != null) {
100:                    maxPosition = maxPosition.optimize(opt, env,
101:                            contextItemType);
102:                }
103:                return this ;
104:            }
105:
106:            /**
107:             * Determine the special properties of this expression
108:             * @return {@link StaticProperty#NON_CREATIVE}.
109:             */
110:
111:            public int computeSpecialProperties() {
112:                int p = super .computeSpecialProperties();
113:                return p | StaticProperty.NON_CREATIVE;
114:            }
115:
116:            /**
117:             * Evaluate the expression
118:             */
119:
120:            public Item evaluateItem(XPathContext c) throws XPathException {
121:                int p = c.getContextPosition();
122:                if (maxPosition == null) {
123:                    NumericValue min = (NumericValue) minPosition
124:                            .evaluateItem(c);
125:                    return BooleanValue.get(p >= min.longValue());
126:                } else {
127:                    NumericValue min = (NumericValue) minPosition
128:                            .evaluateItem(c);
129:                    NumericValue max = (NumericValue) maxPosition
130:                            .evaluateItem(c);
131:                    return BooleanValue.get(p >= min.longValue()
132:                            && p <= max.longValue());
133:                }
134:            }
135:
136:            /**
137:             * Make an iterator over a range of a sequence determined by this position range
138:             */
139:
140:            public SequenceIterator makePositionIterator(SequenceIterator base,
141:                    XPathContext c) throws XPathException {
142:                int low, high;
143:                NumericValue min = (NumericValue) minPosition.evaluateItem(c);
144:                low = (int) min.longValue();
145:                if (maxPosition == null) {
146:                    high = Integer.MAX_VALUE;
147:                } else {
148:                    NumericValue max = (NumericValue) maxPosition
149:                            .evaluateItem(c);
150:                    high = (int) max.longValue();
151:                }
152:                return PositionIterator.make(base, low, high);
153:            }
154:
155:            /**
156:             * Determine the data type of the expression
157:             * @return Type.BOOLEAN
158:             * @param th
159:             */
160:
161:            public ItemType getItemType(TypeHierarchy th) {
162:                return Type.BOOLEAN_TYPE;
163:            }
164:
165:            /**
166:             * Determine the static cardinality
167:             */
168:
169:            public int computeCardinality() {
170:                return StaticProperty.EXACTLY_ONE;
171:            }
172:
173:            /**
174:             * Get the dependencies
175:             */
176:
177:            public int getIntrinsicDependencies() {
178:                return StaticProperty.DEPENDS_ON_POSITION;
179:            }
180:
181:            /**
182:             * Get the immediate sub-expressions of this expression. Default implementation
183:             * returns a zero-length array, appropriate for an expression that has no
184:             * sub-expressions.
185:             *
186:             * @return an iterator containing the sub-expressions of this expression
187:             */
188:
189:            public Iterator iterateSubExpressions() {
190:                if (maxPosition == null) {
191:                    return new MonoIterator(minPosition);
192:                } else {
193:                    return new PairIterator(minPosition, maxPosition);
194:                }
195:            }
196:
197:            /**
198:             * Test if the first and last position are both constant 1
199:             */
200:
201:            public boolean isFirstPositionOnly() {
202:                try {
203:                    return (minPosition instanceof  NumericValue && ((NumericValue) minPosition)
204:                            .longValue() == 1)
205:                            && (maxPosition instanceof  NumericValue && ((NumericValue) maxPosition)
206:                                    .longValue() == 1);
207:                } catch (XPathException e) {
208:                    return false;
209:                }
210:            }
211:
212:            /**
213:             * Test whether the range is focus-dependent. An example of a focus-dependent range is
214:             * (1 to position()). We could treat last() specially but we don't.
215:             */
216:
217:            public boolean hasFocusDependentRange() {
218:                return ((minPosition.getDependencies() & StaticProperty.DEPENDS_ON_FOCUS) != 0)
219:                        || (maxPosition != null && (maxPosition
220:                                .getDependencies() & StaticProperty.DEPENDS_ON_FOCUS) != 0);
221:            }
222:
223:            /**
224:             * Test if the position range matches at most one item
225:             */
226:
227:            public boolean matchesAtMostOneItem() {
228:                return maxPosition != null && minPosition.equals(maxPosition)
229:                        && !hasFocusDependentRange();
230:            }
231:
232:            /**
233:             * If this is an open-ended range with a constant start position, make a TailExpression.
234:             * Otherwise return null
235:             */
236:
237:            public TailExpression makeTailExpression(Expression start) {
238:                if (maxPosition == null && minPosition instanceof  IntegerValue) {
239:                    return new TailExpression(start,
240:                            (int) ((IntegerValue) minPosition).longValue());
241:                } else {
242:                    return null;
243:                }
244:
245:            }
246:
247:            /**
248:             * Diagnostic print of expression structure
249:             */
250:
251:            public void display(int level, NamePool pool, PrintStream out) {
252:                out.println(ExpressionTool.indent(level) + "positionRange");
253:                minPosition.display(level + 1, pool, out);
254:                maxPosition.display(level + 1, pool, out);
255:            }
256:        }
257:
258:        //
259:        // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
260:        // you may not use this file except in compliance with the License. You may obtain a copy of the
261:        // License at http://www.mozilla.org/MPL/
262:        //
263:        // Software distributed under the License is distributed on an "AS IS" basis,
264:        // WITHOUT WARRANTY OF ANY KIND, either express or implied.
265:        // See the License for the specific language governing rights and limitations under the License.
266:        //
267:        // The Original Code is: all this file.
268:        //
269:        // The Initial Developer of the Original Code is Michael H. Kay.
270:        //
271:        // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
272:        //
273:        // Contributor(s): none.
274:        //
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