package gnu.crypto.util; // -*- mode: java; c-basic-offset: 3 -*-
// ---------------------------------------------------------------------------
// $Id: Sequence.java,v 1.2 2005/10/06 04:24:19 rsdio Exp $
//
// Copyright (C) 2004 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
//
// ---------------------------------------------------------------------------
import java.util.AbstractList;
import java.util.LinkedList;
/**
* A monotonic sequence of integers in the finite field 2<sup>32</sup>.
*/
public final class Sequence extends AbstractList {
// Field.
// ------------------------------------------------------------------------
private final Integer[] sequence;
// Constructor.
// ------------------------------------------------------------------------
/**
* Create a sequence of integers from 0 to <i>end</i>, with an increment
* of 1. If <i>end</i> is less than 0, then the sequence will wrap around
* through all positive integers then negative integers until the end
* value is reached. Naturally, this will result in an enormous object,
* so don't do this.
*
* @param end The ending value.
*/
public Sequence(int end) {
this(0, end, 1);
}
/**
* Create a sequence of integers from <i>start</i> to <i>end</i>, with an
* increment of 1. If <i>end</i> is less than <i>start</i>, then the sequence
* will wrap around until the end value is reached. Naturally, this will
* result in an enormous object, so don't do this.
*
* @param start The starting value.
* @param end The ending value.
*/
public Sequence(int start, int end) {
this(start, end, 1);
}
/**
* Create a sequence of integers from <i>start</i> to <i>end</i>, with an
* increment of <i>span</i>. If <i>end</i> is less than <i>start</i>, then
* the sequence will wrap around until the end value is reached. Naturally,
* this will result in an enormous object, so don't do this.
*
* <p><i>span</i> can be negative, resulting in a decresing sequence.
*
* <p>If <i>span</i> is 0, then the sequence will contain {<i>start</i>,
* <i>end</i>} if <i>start</i> != <i>end</i>, or just the singleton
* <i>start</i> if <i>start</i> == <i>end</i>.
*
* @param start The starting value.
* @param end The ending value.
* @param span The increment value.
*/
public Sequence(int start, int end, int span) {
if (span == 0) {
if (start != end) {
sequence = new Integer[] { new Integer(start), new Integer(end) };
} else {
sequence = new Integer[] { new Integer(start) };
}
} else {
LinkedList l = new LinkedList();
for (int i = start; i != end; i += span) {
l.add(new Integer(i));
}
l.add(new Integer(end));
sequence = (Integer[]) l.toArray(new Integer[l.size()]);
}
}
// Instance methods.
// ------------------------------------------------------------------------
public Object get(int index) {
if (index < 0 || index >= size()) {
throw new IndexOutOfBoundsException("index="+index+", size="+size());
}
return sequence[index];
}
public int size() {
return sequence.length;
}
public Object[] toArray() {
return (Object[]) sequence.clone();
}
}