Source Code Cross Referenced for CastableExpression.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.trans.XPathException;
006:        import net.sf.saxon.type.*;
007:        import net.sf.saxon.value.AtomicValue;
008:        import net.sf.saxon.value.BooleanValue;
009:        import net.sf.saxon.value.SequenceType;
010:        import net.sf.saxon.value.ValidationErrorValue;
011:
012:        /**
013:         * Castable Expression: implements "Expr castable as atomic-type?".
014:         * The implementation simply wraps a cast expression with a try/catch.
015:         */
016:
017:        public final class CastableExpression extends UnaryExpression {
018:
019:            AtomicType targetType;
020:            boolean allowEmpty;
021:
022:            public CastableExpression(Expression source, AtomicType target,
023:                    boolean allowEmpty) {
024:                super (source);
025:                this .targetType = target;
026:                this .allowEmpty = allowEmpty;
027:            }
028:
029:            /**
030:             * Simplify the expression
031:             * @return the simplified expression
032:             */
033:
034:            public Expression simplify(StaticContext env) throws XPathException {
035:                operand = operand.simplify(env);
036:                if (operand instanceof  AtomicValue) {
037:                    return BooleanValue.get(effectiveBooleanValue(env
038:                            .makeEarlyEvaluationContext()));
039:                }
040:                return this ;
041:            }
042:
043:            /**
044:             * Type-check the expression
045:             */
046:
047:            public Expression typeCheck(StaticContext env,
048:                    ItemType contextItemType) throws XPathException {
049:                operand = operand.typeCheck(env, contextItemType);
050:                SequenceType atomicType = SequenceType.makeSequenceType(
051:                        Type.ANY_ATOMIC_TYPE,
052:                        (allowEmpty ? StaticProperty.ALLOWS_ZERO_OR_ONE
053:                                : StaticProperty.EXACTLY_ONE));
054:
055:                RoleLocator role = new RoleLocator(RoleLocator.TYPE_OP,
056:                        "castable as", 0, null);
057:                role.setSourceLocator(this );
058:                try {
059:                    operand = TypeChecker.staticTypeCheck(operand, atomicType,
060:                            false, role, env);
061:                } catch (XPathException err) {
062:                    return BooleanValue.FALSE;
063:                }
064:
065:                final TypeHierarchy th = env.getNamePool().getTypeHierarchy();
066:                if (!CastExpression.isPossibleCast(operand.getItemType(th)
067:                        .getPrimitiveType(), targetType.getPrimitiveType())) {
068:                    return BooleanValue.FALSE;
069:                }
070:
071:                if (operand instanceof  AtomicValue) {
072:                    return BooleanValue.get(effectiveBooleanValue(env
073:                            .makeEarlyEvaluationContext()));
074:                }
075:                return this ;
076:            }
077:
078:            /**
079:             * Type-check the expression
080:             */
081:
082:            public Expression optimize(Optimizer opt, StaticContext env,
083:                    ItemType contextItemType) throws XPathException {
084:                operand = operand.optimize(opt, env, contextItemType);
085:                if (operand instanceof  AtomicValue) {
086:                    return BooleanValue.get(effectiveBooleanValue(env
087:                            .makeEarlyEvaluationContext()));
088:                }
089:                return this ;
090:            }
091:
092:            /**
093:             * Is this expression the same as another expression?
094:             */
095:
096:            public boolean equals(Object other) {
097:                return super .equals(other)
098:                        && targetType == ((CastableExpression) other).targetType
099:                        && allowEmpty == ((CastableExpression) other).allowEmpty;
100:            }
101:
102:            /**
103:             * Determine the data type of the result of the Castable expression
104:             * @param th
105:             */
106:
107:            public ItemType getItemType(TypeHierarchy th) {
108:                return Type.BOOLEAN_TYPE;
109:            }
110:
111:            public int computeCardinality() {
112:                return StaticProperty.EXACTLY_ONE;
113:            }
114:
115:            /**
116:             * Determine the special properties of this expression
117:             * @return {@link StaticProperty#NON_CREATIVE}.
118:             */
119:
120:            public int computeSpecialProperties() {
121:                int p = super .computeSpecialProperties();
122:                return p | StaticProperty.NON_CREATIVE;
123:            }
124:
125:            /**
126:             * Evaluate the expression
127:             */
128:
129:            public Item evaluateItem(XPathContext context) {
130:                return BooleanValue.get(effectiveBooleanValue(context));
131:            }
132:
133:            public boolean effectiveBooleanValue(XPathContext context) {
134:                try {
135:                    AtomicValue value = (AtomicValue) operand
136:                            .evaluateItem(context);
137:                    if (value == null) {
138:                        return allowEmpty;
139:                    }
140:                    if (targetType instanceof  BuiltInAtomicType) {
141:                        return !(value.convert(targetType, context, true) instanceof  ValidationErrorValue);
142:                    } else {
143:                        AtomicValue prim = value.convert(
144:                                (AtomicType) targetType.getBuiltInBaseType(),
145:                                context, true);
146:                        if (prim instanceof  ValidationErrorValue) {
147:                            return false;
148:                        }
149:                        AtomicValue val = targetType.makeDerivedValue(prim,
150:                                prim.getStringValueCS(), true);
151:                        return !(val instanceof  ValidationErrorValue);
152:                    }
153:                } catch (XPathException err) {
154:                    return false;
155:                }
156:            }
157:
158:            /**
159:             * Give a string representation of the operator for use in diagnostics
160:             * @return the operator, as a string
161:             */
162:
163:            protected String displayOperator(NamePool pool) {
164:                return "castable as " + targetType.toString(pool);
165:            }
166:
167:        }
168:
169:        //
170:        // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
171:        // you may not use this file except in compliance with the License. You may obtain a copy of the
172:        // License at http://www.mozilla.org/MPL/
173:        //
174:        // Software distributed under the License is distributed on an "AS IS" basis,
175:        // WITHOUT WARRANTY OF ANY KIND, either express or implied.
176:        // See the License for the specific language governing rights and limitations under the License.
177:        //
178:        // The Original Code is: all this file.
179:        //
180:        // The Initial Developer of the Original Code is Michael H. Kay
181:        //
182:        // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
183:        //
184:        // Contributor(s): none.
185:        //
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