1 /*
   2  * Copyright (c) 1997, 2012, 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         StringBuilder s = new StringBuilder();
  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 }