package client.net.sf.saxon.ce.expr;
import client.net.sf.saxon.ce.om.Item;
import client.net.sf.saxon.ce.om.SequenceIterator;
import client.net.sf.saxon.ce.trans.XPathException;
import client.net.sf.saxon.ce.type.*;
import client.net.sf.saxon.ce.value.AtomicValue;
import client.net.sf.saxon.ce.value.BooleanValue;
/**
* Castable Expression: implements "Expr castable as atomic-type?".
* The implementation simply wraps a cast expression with a try/catch.
*/
public final class CastableExpression extends UnaryExpression {
AtomicType targetType;
boolean allowEmpty;
/**
* Create a "castable" expression of the form "source castable as target"
* @param source The source expression
* @param target The type being tested against
* @param allowEmpty true if an empty sequence is acceptable, that is if the expression
* was written as "source castable as target?"
*/
public CastableExpression(Expression source, AtomicType target, boolean allowEmpty) {
super(source);
targetType = target;
this.allowEmpty = allowEmpty;
}
/**
* Simplify the expression
* @return the simplified expression
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
operand = visitor.simplify(operand);
return preEvaluate(visitor);
}
private Expression preEvaluate(ExpressionVisitor visitor) throws XPathException {
if (Literal.isAtomic(operand)) {
return Literal.makeLiteral(
BooleanValue.get(effectiveBooleanValue(visitor.getStaticContext().makeEarlyEvaluationContext())));
}
if (Literal.isEmptySequence(operand)) {
return new Literal(BooleanValue.get(allowEmpty));
}
return this;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
// We need to take care here. The usual strategy of wrapping the operand in an expression that
// does type-checking doesn't work here, because an error in the type checking should be caught,
// while an error in evaluating the expression as written should not.
// SequenceType atomicType = SequenceType.makeSequenceType(
// BuiltInAtomicType.ANY_ATOMIC,
// (allowEmpty ? StaticProperty.ALLOWS_ZERO_OR_ONE
// : StaticProperty.EXACTLY_ONE));
//
// RoleLocator role = new RoleLocator(RoleLocator.TYPE_OP, "castable as", 0, null);
// role.setSourceLocator(this);
// try {
// operand = TypeChecker.staticTypeCheck(operand, atomicType, false, role, env);
// } catch (XPathException err) {
// return Literal.makeLiteral(BooleanValue.FALSE);
// }
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (!CastExpression.isPossibleCast(
operand.getItemType(th).getAtomizedItemType().getPrimitiveType(),
targetType.getPrimitiveType())) {
return Literal.makeLiteral(BooleanValue.FALSE);
}
return preEvaluate(visitor);
}
/**
* Optimize the expression
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.optimize(operand, contextItemType);
return preEvaluate(visitor);
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
targetType == ((CastableExpression)other).targetType &&
allowEmpty == ((CastableExpression)other).allowEmpty;
}
/**
* get HashCode for comparing two expressions. Note that this hashcode gives the same
* result for (A op B) and for (B op A), whether or not the operator is commutative.
*/
@Override
public int hashCode() {
return super.hashCode() ^ targetType.hashCode();
}
/**
* Determine the data type of the result of the Castable expression
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return BuiltInAtomicType.BOOLEAN;
}
public int computeCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Determine the special properties of this expression
* @return {@link StaticProperty#NON_CREATIVE}.
*/
public int computeSpecialProperties() {
int p = super.computeSpecialProperties();
return p | StaticProperty.NON_CREATIVE;
}
/**
* Evaluate the expression
*/
public Item evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
int count = 0;
SequenceIterator iter = operand.iterate(context);
while (true) {
Item item = iter.next();
if (item == null) {
break;
}
AtomicValue av = item.getTypedValue();
count++;
if (count > 1) {
return false;
}
if (!!(av.convert(targetType, true) instanceof ValidationFailure)) {
return false;
}
}
return count != 0 || allowEmpty;
}
}
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is “Incompatible With Secondary Licenses”, as defined by the Mozilla Public License, v. 2.0.