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DTLS Java Async Implementation Based on Bouncy Castle

There is a newer version: 1.0.19

package com.mobius.software.iot.dal.crypto;

/**
 * Mobius Software LTD
 * Copyright 2018, Mobius Software LTD
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

public class AsyncDtlsReplayWindow 
{
	private static final long VALID_SEQ_MASK = 0x0000FFFFFFFFFFFFL;

    private static final long WINDOW_SIZE = 64L;

    private long latestConfirmedSeq = -1;
    private long bitmap = 0;

    public boolean shouldDiscard(long seq)
    {
        if ((seq & VALID_SEQ_MASK) != seq)
        {
            return true;
        }

        if (seq <= latestConfirmedSeq)
        {
            long diff = latestConfirmedSeq - seq;
            if (diff >= WINDOW_SIZE)
            {
                return true;
            }
            if ((bitmap & (1L << diff)) != 0)
            {
                return true;
            }
        }

        return false;
    }

    public void reportAuthenticated(long seq)
    {
        if ((seq & VALID_SEQ_MASK) != seq)
        {
            throw new IllegalArgumentException("'seq' out of range");
        }

        if (seq <= latestConfirmedSeq)
        {
            long diff = latestConfirmedSeq - seq;
            if (diff < WINDOW_SIZE)
            {
                bitmap |= (1L << diff);
            }
        }
        else
        {
            long diff = seq - latestConfirmedSeq;
            if (diff >= WINDOW_SIZE)
            {
                bitmap = 1;
            }
            else
            {
                bitmap <<= (int)diff;        // for earlier JDKs
                bitmap |= 1;
            }
            latestConfirmedSeq = seq;
        }
    }

    public void reset()
    {
        latestConfirmedSeq = -1;
        bitmap = 0;
    }
}