/protocols/smpp/src/main/java/org/mobicents/protocols/smpp/util/SequenceNumberScheme.java

 1/*
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 3 * Copyright 2011, Red Hat, Inc. and individual contributors
 4 * by the @authors tag. See the copyright.txt in the distribution for a
 5 * full listing of individual contributors.
 6 *
 7 * This is free software; you can redistribute it and/or modify it
 8 * under the terms of the GNU Lesser General Public License as
 9 * published by the Free Software Foundation; either version 2.1 of
10 * the License, or (at your option) any later version.
11 *
12 * This software is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this software; if not, write to the Free
19 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21 */
22
23package org.mobicents.protocols.smpp.util;
24
25/**
26 * SMPP packet sequence numbering scheme interface. Implementations of this
27 * interface provide a {@link org.mobicents.protocols.smpp.Session} with a unique number for
28 * each call to <code>nextNumber</code>. This number is used as the packet's
29 * sequence number in the SMPP header. The default implementation (
30 * {@link DefaultSequenceScheme}) counts monotonically from 1 upwards for each
31 * number requested. While this is the SMPP specification's recommended
32 * behaviour, there is no requirement for 2 sequentially-requested numbers to be
33 * numerically sequential.
34 * 
35 * @version $Id: SequenceNumberScheme.java 452 2009-01-15 16:56:36Z orank $
36 */
37public interface SequenceNumberScheme {
38
39    /**
40     * Constant that can be returned from the <code>peek</code> methods to
41     * indicate that the peek operation is not supported.
42     */
43    long PEEK_UNSUPPORTED = -1;
44
45    /**
46     * Get the next number in this sequence's scheme. An implementation of this
47     * interface <b>must </b> guard against multi-threaded access to this method
48     * to prevent more than one thread getting the same sequence number.
49     */
50    long nextNumber();
51
52    /**
53     * Get the next number in this sequence's scheme without causing it to move
54     * to the next-in-sequence. This method returns the number that will be
55     * returned by the next call to <code>nextNumber</code> without actually
56     * increasing the sequence. Multiple calls to <code>peek</code> will
57     * return the same number until a call to <code>nextNumber</code> is made.
58     */
59    long peek();
60
61    /**
62     * Get the nth next number in this sequence's scheme without causing it to
63     * move to the next-in-sequence. This method returns the <code>nth</code>
64     * next number in the sequence. This is an optional operation. If a sequence
65     * numbering scheme does not support this operation, it should always return
66     * {@link #PEEK_UNSUPPORTED} to the caller.
67     */
68    long peek(long nth);
69
70    /**
71     * Reset the sequence scheme to the beginning of the sequence.
72     */
73    void reset();
74}
75