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backoff.cc
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1 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
2 /*
3  * Copyright (c) 2007, Emmanuelle Laprise
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation;
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17  *
18  * Author: Emmanuelle Laprise <emmanuelle.laprise@bluekazoo.ca>
19  */
20 
21 #include "backoff.h"
22 #include "ns3/log.h"
23 
24 NS_LOG_COMPONENT_DEFINE ("Backoff");
25 
26 namespace ns3 {
27 
28 Backoff::Backoff ()
29 {
30  m_slotTime = MicroSeconds (1);
31  m_minSlots = 1;
32  m_maxSlots = 1000;
33  m_ceiling = 10;
34  m_maxRetries = 1000;
35  m_rng = CreateObject<UniformRandomVariable> ();
36 
37  ResetBackoffTime ();
38 }
39 
40 Backoff::Backoff(Time slotTime, uint32_t minSlots, uint32_t maxSlots, uint32_t ceiling, uint32_t maxRetries)
41 {
42  m_slotTime = slotTime;
43  m_minSlots = minSlots;
44  m_maxSlots = maxSlots;
45  m_ceiling = ceiling;
46  m_maxRetries = maxRetries;
47  m_rng = CreateObject<UniformRandomVariable> ();
48 }
49 
50 Time
51 Backoff::GetBackoffTime (void)
52 {
53  uint32_t ceiling;
54 
55  if ((m_ceiling > 0) &&(m_numBackoffRetries > m_ceiling))
56  {
57  ceiling = m_ceiling;
58  }
59  else
60  {
61  ceiling = m_numBackoffRetries;
62  }
63 
64  uint32_t minSlot = m_minSlots;
65  uint32_t maxSlot = (uint32_t)pow (2, ceiling) - 1;
66  if (maxSlot > m_maxSlots)
67  {
68  maxSlot = m_maxSlots;
69  }
70 
71  uint32_t backoffSlots = (uint32_t)m_rng->GetValue (minSlot, maxSlot);
72 
73  Time backoff = Time (backoffSlots * m_slotTime);
74  return backoff;
75 }
76 
77 void
78 Backoff::ResetBackoffTime (void)
79 {
80  m_numBackoffRetries = 0;
81 }
82 
83 bool
84 Backoff::MaxRetriesReached (void)
85 {
86  return (m_numBackoffRetries >= m_maxRetries);
87 }
88 
89 void
90 Backoff::IncrNumRetries (void)
91 {
92  m_numBackoffRetries++;
93 }
94 
95 int64_t
96 Backoff::AssignStreams (int64_t stream)
97 {
98  NS_LOG_FUNCTION (this << stream);
99  m_rng->SetStream (stream);
100  return 1;
101 }
102 
103 } // namespace ns3