package net.sf.saxon.expr;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.AtomicType;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.SequenceExtent;
/**
* An AtomicSequenceConverter is an expression that performs a cast on each member of
* a supplied sequence
*/
public final class AtomicSequenceConverter extends UnaryExpression {
private AtomicType requiredItemType;
private BuiltInAtomicType requiredPrimitiveType;
/**
* Constructor
* @param sequence this must be a sequence of atomic values. This is not checked; a ClassCastException
* will occur if the precondition is not satisfied.
* @param requiredItemType the item type to which all items in the sequence should be converted,
* using the rules for "cast as".
*/
public AtomicSequenceConverter(Expression sequence, AtomicType requiredItemType) {
super(sequence);
this.requiredItemType = requiredItemType;
requiredPrimitiveType = (BuiltInAtomicType)requiredItemType.getPrimitiveItemType();
ExpressionTool.copyLocationInfo(sequence, this);
}
/**
* Get the required (target) primitive type
* @return the required primitive type
*/
public AtomicType getRequiredPrimitiveType() {
return requiredPrimitiveType;
}
/**
* Simplify an expression
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
operand = visitor.simplify(operand);
if (operand instanceof Literal) {
return Literal.makeLiteral(
new SequenceExtent(iterate(visitor.getStaticContext().makeEarlyEvaluationContext())));
}
return this;
}
/**
* Type-check the expression
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
operand = visitor.typeCheck(operand, contextItemType);
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (th.isSubType(operand.getItemType(th), requiredItemType)) {
return operand;
} else if (!Cardinality.allowsMany(operand.getCardinality())) {
CastExpression cast = new CastExpression(operand, requiredItemType,
(operand.getCardinality() & StaticProperty.ALLOWS_ZERO) != 0);
ExpressionTool.copyLocationInfo(this, cast);
return cast;
} else {
return this;
}
}
/**
* Determine the special properties of this expression
* @return {@link 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
*/
public Expression copy() {
return new AtomicSequenceConverter(getBaseExpression().copy(), requiredItemType);
}
/**
* Iterate over the sequence of values
*/
public SequenceIterator iterate(final XPathContext context) throws XPathException {
SequenceIterator base = operand.iterate(context);
ItemMappingFunction converter = new ItemMappingFunction() {
public Item map(Item item) throws XPathException {
return ((AtomicValue)item).convert(requiredPrimitiveType, true, context).asAtomic();
}
};
return new ItemMappingIterator(base, converter);
}
/**
* Evaluate as an Item. This should only be called if the AtomicSequenceConverter has cardinality zero-or-one
*/
public Item evaluateItem(XPathContext context) throws XPathException {
Item item = operand.evaluateItem(context);
if (item==null) return null;
return ((AtomicValue)item).convert(requiredPrimitiveType, true, context).asAtomic();
}
/**
* Determine the data type of the items returned by the expression, if possible
* @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE,
* or Type.ITEM (meaning not known in advance)
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return requiredItemType;
}
/**
* Determine the static cardinality of the expression
*/
public int computeCardinality() {
return operand.getCardinality();
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return super.equals(other) &&
requiredPrimitiveType == ((AtomicSequenceConverter)other).requiredPrimitiveType;
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter destination) {
destination.startElement("convertItems");
destination.emitAttribute("to", requiredItemType.toString(destination.getNamePool()));
operand.explain(destination);
destination.endElement();
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//