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.om.ValueRepresentation;
import client.net.sf.saxon.ce.trans.XPathException;
import client.net.sf.saxon.ce.tree.iter.GroundedIterator;
import client.net.sf.saxon.ce.value.Value;
/**
* A LastItemExpression returns the last item in the sequence returned by a given
* base expression. The evaluation strategy is to read the input sequence with a one-item lookahead.
*/
public final class LastItemExpression extends SingleItemFilter {
/**
* Constructor
* @param base A sequence expression denoting sequence whose first item is to be returned
*/
public LastItemExpression(Expression base) {
operand = base;
adoptChildExpression(base);
computeStaticProperties();
}
/**
* Evaluate the expression
*/
public Item evaluateItem(XPathContext context) throws XPathException {
SequenceIterator forwards = operand.iterate(context);
if ((forwards.getProperties() & SequenceIterator.GROUNDED) != 0) {
ValueRepresentation repr = ((GroundedIterator)forwards).materialize();
Value val = Value.asValue(repr);
int length = val.getLength();
return val.itemAt(length - 1);
} else {
Item current = null;
while (true) {
Item item = forwards.next();
if (item == null) {
return current;
}
current = item;
}
}
}
}
// 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.