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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// 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.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.RoleLocator;
import net.sf.saxon.expr.parser.TypeChecker;
import net.sf.saxon.om.GroundedValue;
import net.sf.saxon.om.NamespaceResolver;
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.ListType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.*;
/**
* Expression class for a cast to a List type
*/
public class CastableToList extends UnaryExpression {
private ListType targetType;
private boolean allowEmpty;
/*@Nullable*/
private NamespaceResolver nsResolver = null;
public CastableToList(Expression source, ListType targetType, boolean allowEmpty) {
super(source);
this.targetType = targetType;
this.allowEmpty = allowEmpty;
}
public boolean isAllowEmpty(){
return allowEmpty;
}
public ListType 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);
SequenceType atomicType = SequenceType.makeSequenceType(BuiltInAtomicType.STRING, (allowEmpty ? StaticProperty.ALLOWS_ZERO_OR_ONE : StaticProperty.EXACTLY_ONE));
RoleLocator role = new RoleLocator(RoleLocator.TYPE_OP, "castable as", 0);
//role.setSourceLocator(this);
operand = TypeChecker.staticTypeCheck(operand, atomicType, false, role, visitor);
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
boolean maybeString = th.relationship(operand.getItemType(th), BuiltInAtomicType.STRING) != TypeHierarchy.DISJOINT;
boolean maybeUntyped = th.relationship(operand.getItemType(th), BuiltInAtomicType.UNTYPED_ATOMIC) != TypeHierarchy.DISJOINT;
if (!maybeString && !maybeUntyped){
// Casting from other types can never succeed
return Literal.makeLiteral(BooleanValue.FALSE);
}
if (operand instanceof Literal) {
GroundedValue literalOperand = ((Literal) operand).getValue();
if (literalOperand instanceof AtomicValue) {
return Literal.makeLiteral(BooleanValue.get(effectiveBooleanValue(visitor.getStaticContext().makeEarlyEvaluationContext())));
}
if (literalOperand instanceof EmptySequence) {
return Literal.makeLiteral(BooleanValue.get((allowEmpty ? true : false)));
}
}
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 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;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
CastableToList c = new CastableToList(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 {
AtomicValue value = (AtomicValue) operand.evaluateItem(context);
if (value == null) {
return allowEmpty;
}
try {
CastToList.cast(value.getStringValue(), targetType, nsResolver, context.getConfiguration().getConversionRules());
return true;
} catch (XPathException err) {
return false;
}
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
targetType == ((CastableToList) other).targetType &&
allowEmpty == ((CastableToList) other).allowEmpty &&
nsResolver == ((CastableToList) 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("castableToList");
out.emitAttribute("as", targetType.toString());
operand.explain(out);
out.endElement();
}
}
// Copyright (c) 2011 Saxonica Limited. All rights reserved.