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Java > Open Source Codes > org > columba > ristretto > message > MessageIDGenerator


1 /* ***** BEGIN LICENSE BLOCK *****
2  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
3  *
4  * The contents of this file are subject to the Mozilla Public License Version
5  * 1.1 (the "License"); you may not use this file except in compliance with
6  * the License. You may obtain a copy of the License at
7  * http://www.mozilla.org/MPL/
8  *
9  * Software distributed under the License is distributed on an "AS IS" basis,
10  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
11  * for the specific language governing rights and limitations under the
12  * License.
13  *
14  * The Original Code is Ristretto Mail API.
15  *
16  * The Initial Developers of the Original Code are
17  * Timo Stich and Frederik Dietz.
18  * Portions created by the Initial Developers are Copyright (C) 2004
19  * All Rights Reserved.
20  *
21  * Contributor(s):
22  *
23  * Alternatively, the contents of this file may be used under the terms of
24  * either the GNU General Public License Version 2 or later (the "GPL"), or
25  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
26  * in which case the provisions of the GPL or the LGPL are applicable instead
27  * of those above. If you wish to allow use of your version of this file only
28  * under the terms of either the GPL or the LGPL, and not to allow others to
29  * use your version of this file under the terms of the MPL, indicate your
30  * decision by deleting the provisions above and replace them with the notice
31  * and other provisions required by the GPL or the LGPL. If you do not delete
32  * the provisions above, a recipient may use your version of this file under
33  * the terms of any one of the MPL, the GPL or the LGPL.
34  *
35  * ***** END LICENSE BLOCK ***** */
36 package org.columba.ristretto.message;
37
38 import java.net.InetAddress JavaDoc;
39 import java.net.UnknownHostException JavaDoc;
40
41 /**
42  * Generator for unique message-ids (UIDs).
43  *
44  *
45  * @author Timo Stich <tstich@users.sourceforge.net>
46  */
47 public class MessageIDGenerator {
48     /**
49      * Constructs the MessageIDGenerator.
50      */
51     public MessageIDGenerator() {
52     }
53
54     /**
55      *
56      * Generate a unique Message-ID
57      * @return a UID
58      *
59      *
60      */
61     public static String JavaDoc generate() {
62         String JavaDoc hostname = null;
63
64         try {
65             hostname = InetAddress.getLocalHost().getHostName();
66         } catch (UnknownHostException JavaDoc e) {
67             hostname = "";
68         }
69
70         long currentTime = System.currentTimeMillis();
71         long randomNumber = Double.doubleToLongBits(Math.random());
72
73         StringBuffer JavaDoc result = new StringBuffer JavaDoc();
74
75         result.append("<");
76         result.append(Long.toString(Math.abs(currentTime), 36));
77         result.append(".");
78         result.append(Long.toString(Math.abs(randomNumber), 36));
79         result.append("@");
80
81         if (hostname.length() == 0) {
82             result.append(hostname);
83         } else {
84             result.append("a");
85             randomNumber = (Double.doubleToLongBits(Math.random()) & 0xFFFFFFFFL);
86             result.append(Long.toString(Math.abs(randomNumber), 36));
87         }
88
89         result.append(">");
90
91         return result.toString();
92     }
93
94 }
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