/*

 * Copyright (c) 2000, 2007, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5.internal;

import sun.security.krb5.Confounder;

public class LocalSeqNumber implements SeqNumber {

    private int lastSeqNumber;

    public LocalSeqNumber() {

        randInit();

    }

    public LocalSeqNumber(int start) {

        init(start);

    }

    public LocalSeqNumber(Integer start) {

        init(start.intValue());

    }

    public synchronized void randInit() {

        /*

         * Sequence numbers fall in the range 0 through 2^32 - 1 and wrap

         * to zero following the value 2^32 - 1.

         * Previous implementations used signed sequence numbers.

         * Workaround implementation incompatibilities by not generating

         * initial sequence numbers greater than 2^30, as done

         * in MIT distribution.

         */

        // get the random confounder

        byte[] data = Confounder.bytes(4);

        data[0] = (byte)(data[0] & 0x3f);

        int result = ((data[3] & 0xff) |

                        ((data[2] & 0xff) << 8) |

                        ((data[1] & 0xff) << 16) |

                        ((data[0] & 0xff) << 24));

        if (result == 0) {

           result = 1;

        }

        lastSeqNumber = result;

    }

    public synchronized void init(int start) {

        lastSeqNumber = start;

    }

    public synchronized int current() {

        return lastSeqNumber;

    }

    public synchronized int next() {

        return lastSeqNumber + 1;

    }

    public synchronized int step() {

        return ++lastSeqNumber;

    }

}