net.sf.saxon.expr.ReverseRangeIterator Maven / Gradle / Ivy
package net.sf.saxon.expr;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.LookaheadIterator;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.Int64Value;
/**
* Iterator that produces numeric values in a monotonic sequence,
* ascending or descending. Although a range expression (N to M) is always
* in ascending order, applying the reverse() function will produce
* a RangeIterator that works in descending order.
*/
public class ReverseRangeIterator implements SequenceIterator,
ReversibleIterator, LastPositionFinder, LookaheadIterator {
long start;
long currentValue;
long limit;
/**
* Create an iterator over a range of integers in monotonic descending order
* @param start the first integer to be delivered (the highest in the range)
* @param end the last integer to be delivered (the lowest in the range). Must be <= start
*/
public ReverseRangeIterator(long start, long end) {
this.start = start;
currentValue = start + 1;
limit = end;
}
public boolean hasNext() {
return currentValue > limit;
}
public Item next() {
if (--currentValue < limit) {
return null;
}
return Int64Value.makeIntegerValue(currentValue);
}
public Item current() {
if (currentValue < limit) {
return null;
} else {
return Int64Value.makeIntegerValue(currentValue);
}
}
public int position() {
if (currentValue < limit) {
return -1;
} else {
return (int)(start - currentValue + 1);
}
}
public int getLastPosition() {
return (int)((start - limit) + 1);
}
public SequenceIterator getAnother() throws XPathException {
return new ReverseRangeIterator(start, limit);
}
/**
* 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 net.sf.saxon.om.SequenceIterator#GROUNDED}, {@link net.sf.saxon.om.SequenceIterator#LAST_POSITION_FINDER},
* and {@link net.sf.saxon.om.SequenceIterator#LOOKAHEAD}. 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 LOOKAHEAD | LAST_POSITION_FINDER;
}
public SequenceIterator getReverseIterator() {
return new RangeIterator(limit, start);
}
}
//
// 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.
//