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An OSGi bundle for Saxon-HE
package net.sf.saxon.expr;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.om.*;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.type.UnionType;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.BooleanValue;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.EmptySequence;
/**
* Expression class for a cast to a union type
*/
public class CastableToUnion extends UnaryExpression {
private UnionType targetType;
private boolean allowEmpty;
/*@Nullable*/
private NamespaceResolver nsResolver = null;
public CastableToUnion(Expression source, UnionType targetType, boolean allowEmpty) {
super(source);
this.targetType = targetType;
this.allowEmpty = allowEmpty;
}
public boolean isAllowEmpty() {
return allowEmpty;
}
public UnionType getTargetType() {
return targetType;
}
public NamespaceResolver getNamespaceResolver() {
return nsResolver;
}
/**
* Simplify the expression
*
* @param visitor an expression visitor
* @return the simplified expression
*/
/*@NotNull*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
if (targetType.isNamespaceSensitive()) {
StaticContext env = visitor.getStaticContext();
nsResolver = env.getNamespaceResolver();
}
operand = visitor.simplify(operand);
return this;
}
/**
* Type-check the expression
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
// ItemType sourceItemType = operand.getItemType(th);
// if (sourceItemType instanceof ErrorType) {
// return Literal.makeLiteral(BooleanValue.get(allowEmpty));
// }
//
if (operand instanceof Literal) {
GroundedValue literalOperand = ((Literal) operand).getValue();
if (literalOperand instanceof AtomicValue) {
AtomicValue av = evaluateItem(visitor.getStaticContext().makeEarlyEvaluationContext());
return Literal.makeLiteral(av);
}
if (literalOperand instanceof EmptySequence) {
return Literal.makeLiteral(BooleanValue.get(allowEmpty));
}
}
return this;
}
/**
* Perform optimisation of an expression and its subexpressions.
*
* This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.
*
* @param visitor an expression visitor
* @param contextItemType the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link net.sf.saxon.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws net.sf.saxon.trans.XPathException
* if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
Expression e2 = super.optimize(visitor, contextItemType);
if (e2 != this) {
return e2;
}
// if the operand can't be empty, then set allowEmpty to false to provide more information for analysis
if (!Cardinality.allowsZero(operand.getCardinality())) {
allowEmpty = false;
resetLocalStaticProperties();
}
return this;
}
/**
* Get the static cardinality of the expression
*/
public int computeCardinality() {
return (allowEmpty && Cardinality.allowsZero(operand.getCardinality())
? StaticProperty.ALLOWS_ZERO_OR_ONE : StaticProperty.EXACTLY_ONE);
}
/**
* Get the static type of the expression
*
* @param th the type hierarchy cache
*/
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
return BuiltInAtomicType.BOOLEAN;
}
/**
* Determine the special properties of this expression
*
* @return {@link net.sf.saxon.expr.StaticProperty#NON_CREATIVE}.
*/
public int computeSpecialProperties() {
int p = super.computeSpecialProperties();
return p | StaticProperty.NON_CREATIVE;
}
public boolean allowsEmpty() {
return allowEmpty;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
CastableToUnion c = new CastableToUnion(getBaseExpression().copy(), targetType, allowEmpty);
c.nsResolver = nsResolver;
return c;
}
/**
* Evaluate the expression
*/
public BooleanValue evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
// This method does its own atomization so that it can distinguish between atomization
// failures and casting failures
int count = 0;
SequenceIterator iter = operand.iterate(context);
while (true) {
Item item = iter.next();
if (item == null) {
break;
}
if (item instanceof NodeInfo) {
Sequence atomizedValue = ((NodeInfo)item).atomize();
int length = SequenceTool.getLength(atomizedValue);
count += length;
if (count > 1) {
return false;
}
if (length != 0) {
AtomicValue av = (AtomicValue)atomizedValue.head();
if (!net.sf.saxon.expr.CastToUnion.castable(av, targetType, nsResolver, context)) {
return false;
}
}
} else {
AtomicValue av = (AtomicValue)item;
count++;
if (count > 1) {
return false;
}
if (!net.sf.saxon.expr.CastToUnion.castable(av, targetType, nsResolver, context)) {
return false;
}
}
}
return count != 0 || allowEmpty;
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
targetType == ((CastableToUnion) other).targetType &&
allowEmpty == ((CastableToUnion) other).allowEmpty &&
nsResolver == ((CastableToUnion) other).nsResolver;
}
/**
* get HashCode for comparing two expressions.
*/
@Override
public int hashCode() {
return super.hashCode() ^ targetType.hashCode();
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
* In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
*/
public String toString() {
return operand.toString() + " castable as " + targetType.getEQName();
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter out) {
out.startElement("castableToUnion");
out.emitAttribute("as", targetType.getEQName());
operand.explain(out);
out.endElement();
}
}
// Copyright (c) 2011 Saxonica Limited. All rights reserved.
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