package net.sf.saxon.option.exslt;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.UnfailingIterator;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.DoubleValue;
/**
* This class implements extension functions in the
* http://exslt.org/random namespace.
*
* @author Martin Szugat
* @version 1.0, 30.06.2004
* Rewritten by Michael Kay to generate a SequenceIterator
*/
public abstract class Random {
/**
* Returns a sequence of random numbers
* between 0 and 1.
* @param numberOfItems number of random items
* in the sequence.
* @param seed the initial seed.
* @return sequence of random numbers as an iterator.
* @throws IllegalArgumentException
* <code>numberOfItems</code> is not positive.
*/
public static SequenceIterator randomSequence(int numberOfItems, double seed)
throws IllegalArgumentException {
if (numberOfItems < 1) {
throw new IllegalArgumentException("numberOfItems supplied to randomSequence() must be positive");
}
long javaSeed = Double.doubleToLongBits(seed);
return new RandomIterator(numberOfItems, javaSeed);
}
/**
* Returns a sequence of random numbers
* between 0 and 1.
* @param numberOfItems number of random items
* in the sequence.
* @return sequence of random numbers.
* @throws IllegalArgumentException
* <code>numberOfItems</code> is not positive.
*/
public static SequenceIterator randomSequence(int numberOfItems)
throws IllegalArgumentException {
return randomSequence(numberOfItems, System.currentTimeMillis());
}
/**
* Returns a single random number X
* between 0 and 1.
* @return sequence random number.
*/
public static DoubleValue randomSequence() throws XPathException {
return (DoubleValue)randomSequence(1).next();
}
/**
* Iterator over a sequence of random numbers
*/
private static class RandomIterator implements UnfailingIterator {
protected int position = 0;
protected Item current;
private int count;
private long seed;
private java.util.Random generator;
public RandomIterator(int count, long seed) {
this.count = count;
this.seed = seed;
generator = new java.util.Random(seed);
}
/**
* Get the next item in the sequence. <BR>
* @return the next item, or null if there are no more items.
*/
public Item next() {
if (position++ >= count) {
current = null;
position = -1;
return null;
} else {
current = new DoubleValue(generator.nextDouble());
return current;
}
}
/**
* Get the current node in the sequence.
* @return the node returned by the most recent call on next()
*/
public final Item current() {
return current;
}
/**
* Get the current position
* @return the position of the most recent node returned by next()
*/
public final int position() {
return position;
}
public void close() {
}
/**
* Get another SequenceIterator that iterates over the same items as the original,
* but which is repositioned at the start of the sequence.
*
* @return a SequenceIterator that iterates over the same items,
* positioned before the first item
*/
public SequenceIterator getAnother() {
return new RandomIterator(count, seed);
}
public int getProperties() {
return 0;
}
}
}
//
// 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 Martin Szugat.
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): Michael H. Kay.
//