1 /*

     2  * Copyright (c) 1997, 2013, Oracle and/or its affiliates. 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.  Oracle designates this

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

     9  * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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

    23  * questions.

    24  */

    25 

    26 /*

    27  * @(#)UniqueValue.java       1.6 02/03/27

    28  */

    29 

    30 

    31 

    32 package com.sun.xml.internal.messaging.saaj.packaging.mime.internet;

    33 

    34 

    35 /**

    36  * This is a utility class that generates unique values. The generated

    37  * String contains only US-ASCII characters and hence is safe for use

    38  * in RFC822 headers. <p>

    39  *

    40  * This is a package private class.

    41  *

    42  * @author John Mani

    43  * @author Max Spivak

    44  * @author Bill Shannon

    45  */

    46 

    47 class UniqueValue {

    48     /**

    49      * A global part number.  Access is not synchronized because the

    50      * value is only one part of the unique value and so doesn't need

    51      * to be accurate.

    52      */

    53     private static int part = 0;

    54 

    55     /**

    56      * Get a unique value for use in a multipart boundary string.

    57      *

    58      * This implementation generates it by concatenating a global

    59      * part number, a newly created object's <code>hashCode()</code>,

    60      * and the current time (in milliseconds).

    61      */

    62     public static String getUniqueBoundaryValue() {

    63         StringBuffer s = new StringBuffer();

    64 

    65         // Unique string is ----=_Part_<part>_<hashcode>.<currentTime>

    66         s.append("----=_Part_").append(part++).append("_").

    67           append(s.hashCode()).append('.').

    68           append(System.currentTimeMillis());

    69         return s.toString();

    70     }

    71 }