package client.net.sf.saxon.ce.tree.iter;
import client.net.sf.saxon.ce.expr.LastPositionFinder;
import client.net.sf.saxon.ce.om.GroundedValue;
import client.net.sf.saxon.ce.om.Item;
import client.net.sf.saxon.ce.om.SequenceIterator;
import client.net.sf.saxon.ce.value.AtomicValue;
import client.net.sf.saxon.ce.value.SingletonItem;
/**
* SingletonIterator: an iterator over a sequence of zero or one values
*/
public class SingletonIterator implements UnfailingIterator,
LastPositionFinder, GroundedIterator {
private Item item;
private int position = 0;
/**
* Private constructor: external classes should use the factory method
* @param value the item to iterate over
*/
private SingletonIterator(Item value) {
this.item = value;
}
/**
* Factory method.
* @param item the item to iterate over
* @return a SingletonIterator over the supplied item, or an EmptyIterator
* if the supplied item is null.
*/
public static UnfailingIterator makeIterator(Item item) {
if (item==null) {
return EmptyIterator.getInstance();
} else {
return new SingletonIterator(item);
}
}
public Item next() {
if (position == 0) {
position = 1;
return item;
} else if (position == 1) {
position = -1;
return null;
} else {
return null;
}
}
public Item current() {
if (position == 1) {
return item;
} else {
return null;
}
}
/**
* Return the current position in the sequence.
* @return 0 before the first call on next(); 1 before the second call on next(); -1 after the second
* call on next().
*/
public int position() {
return position;
}
public int getLastPosition() {
return 1;
}
public SequenceIterator getAnother() {
return new SingletonIterator(item);
}
public SequenceIterator getReverseIterator() {
return new SingletonIterator(item);
}
public Item getValue() {
return item;
}
/**
* Return a Value containing all the items in the sequence returned by this
* SequenceIterator
*
* @return the corresponding Value. If the value is a closure or a function call package, it will be
* evaluated and expanded.
*/
public GroundedValue materialize() {
if (item instanceof AtomicValue) {
return (AtomicValue)item;
} else {
return new SingletonItem(item);
}
}
/**
* Get properties of this iterator, as a bit-significant integer.
*
* @return the properties of this iterator. This will be some combination of
* properties such as {@link #GROUNDED}, {@link #LAST_POSITION_FINDER}. It is always
* acceptable to return the value zero, indicating that there are no known special properties.
* It is acceptable for the properties of the iterator to change depending on its state.
*/
public int getProperties() {
return GROUNDED | LAST_POSITION_FINDER ;
}
}
// 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.