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103 lines
3.8 KiB
Java
103 lines
3.8 KiB
Java
/* -*- Mode: java; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* The contents of this file are subject to the Mozilla Public
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* License Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing
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* rights and limitations under the License.
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*
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* The Original Code is the Grendel mail/news client.
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*
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* The Initial Developer of the Original Code is Netscape Communications
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* Corporation. Portions created by Netscape are
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* Copyright (C) 1997 Netscape Communications Corporation. All
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* Rights Reserved.
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*
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* Contributor(s):
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*
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* Created: Jamie Zawinski <jwz@netscape.com>, 26 Sep 1997.
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*/
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package grendel.util;
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import calypso.util.ByteBuf;
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/** This class generates globally-unique message IDs.
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These IDs conform to RFC 822, RFC 1036, and the
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so-called son-of-1036 draft.
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*/
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public class MessageIDGenerator {
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private MessageIDGenerator() { } // only static methods
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/** Generates a new Message-ID string.
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@param hostname The `domain' part of the ID to generate.
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<P>
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Generally, this should be the fully-qualified name of
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the local host. In situations where that is impossible
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to determine, or where the local host name might be
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considered confidential information, the host part of
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the return address of the authoring user will do.
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<P>
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If the provided host name is not syntactically valid,
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an error is signalled.
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<P>
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The host name may be null; in that case, a random
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sequence of characters will be used for the host name,
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resulting in a syntactically valid Message-ID. Note,
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however, that this is strongly discouraged by the
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relevant RFCs: Message-IDs should have valid host
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names in them if at all possible.
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@return The new ID, a String.
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*/
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public static String generate(String host_name) {
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if (host_name != null) {
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checkHostName(host_name);
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if (host_name.length() == 0)
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host_name = null;
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}
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int radix = 36; // keep the strings short
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long time = System.currentTimeMillis(); // millisec resolution
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long salt = Double.doubleToLongBits(Math.random()); // 64 random bits
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ByteBuf out = ByteBuf.Alloc();
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out.append((byte) '<');
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out.append(Long.toString(Math.abs(time), radix));
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out.append((byte) '.');
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out.append(Long.toString(Math.abs(salt), radix));
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out.append((byte) '@');
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if (host_name != null)
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out.append(host_name);
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else {
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out.append((byte) 'h'); // domain part must begin with a letter
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salt = (Double.doubleToLongBits(Math.random()) & 0xFFFFFFFFL); // 32 bits
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out.append(Long.toString(Math.abs(salt), radix));
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}
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out.append((byte) '>');
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String result = out.toString();
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ByteBuf.Recycle(out);
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return result;
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}
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private static void checkHostName(String string) {
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int L = string.length();
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for (int i = 0; i < L; i++) {
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char c = string.charAt(i);
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if (!Character.isLetterOrDigit(c) && c != '-' && c != '_' && c != '.')
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throw new Error("illegal character in host name for Message-ID: " +
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"`" +
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new String(new char[] { c }) +
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"' (" + string + ")");
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}
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}
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}
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