1 /*

     2  * Portions Copyright 2000-2007 Sun Microsystems, Inc.  All Rights Reserved.

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Sun designates this

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

     9  * by Sun in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

    21  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 

    26 /*

    27  *

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

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

    30  */

    31 

    32 package sun.security.krb5.internal;

    33 

    34 import sun.security.krb5.Confounder;

    35 

    36 public class LocalSeqNumber implements SeqNumber {

    37     private int lastSeqNumber;

    38 

    39     public LocalSeqNumber() {

    40         randInit();

    41     }

    42 

    43     public LocalSeqNumber(int start) {

    44         init(start);

    45     }

    46 

    47     public LocalSeqNumber(Integer start) {

    48         init(start.intValue());

    49     }

    50 

    51     public synchronized void randInit() {

    52         /*

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

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

    55          * Previous implementations used signed sequence numbers.

    56          * Workaround implementation incompatibilities by not generating

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

    58          * in MIT distribution.

    59          */

    60         // get the random confounder

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

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

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

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

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

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

    67         if (result == 0) {

    68            result = 1;

    69         }

    70         lastSeqNumber = result;

    71     }

    72 

    73     public synchronized void init(int start) {

    74         lastSeqNumber = start;

    75     }

    76 

    77     public synchronized int current() {

    78         return lastSeqNumber;

    79     }

    80 

    81     public synchronized int next() {

    82         return lastSeqNumber + 1;

    83     }

    84 

    85     public synchronized int step() {

    86         return ++lastSeqNumber;

    87     }

    88 

    89 }