/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2007, Emmanuelle Laprise

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Emmanuelle Laprise <emmanuelle.laprise@bluekazoo.ca>

 */

#include "backoff.h"

#include "ns3/log.h"

namespace ns3 {

NS_LOG_COMPONENT_DEFINE ("Backoff");

Backoff::Backoff () 

{

  m_slotTime = MicroSeconds (1);

  m_minSlots = 1;

  m_maxSlots = 1000;

  m_ceiling = 10;

  m_maxRetries = 1000;

  m_numBackoffRetries = 0;

  m_rng = CreateObject<UniformRandomVariable> ();

  ResetBackoffTime ();

}

Backoff::Backoff(Time slotTime, uint32_t minSlots, uint32_t maxSlots, uint32_t ceiling, uint32_t maxRetries)

{

  m_slotTime = slotTime;

  m_minSlots = minSlots;

  m_maxSlots = maxSlots;

  m_ceiling = ceiling;

  m_maxRetries = maxRetries;

  m_numBackoffRetries = 0;

  m_rng = CreateObject<UniformRandomVariable> ();

}

Time

Backoff::GetBackoffTime (void)

{

  uint32_t ceiling;

  if ((m_ceiling > 0) &&(m_numBackoffRetries > m_ceiling))

    {

      ceiling = m_ceiling;

    }

  else

    {

      ceiling = m_numBackoffRetries;

    }

  uint32_t minSlot = m_minSlots;

  uint32_t maxSlot = (uint32_t)pow (2, ceiling) - 1;

  if (maxSlot > m_maxSlots)

    {

      maxSlot = m_maxSlots;

    }

  uint32_t backoffSlots = (uint32_t)m_rng->GetValue (minSlot, maxSlot);

  Time backoff = Time (backoffSlots * m_slotTime);

  return backoff;

}

void 

Backoff::ResetBackoffTime (void)

{

  m_numBackoffRetries = 0;

}

bool 

Backoff::MaxRetriesReached (void) 

{

  return (m_numBackoffRetries >= m_maxRetries);

}

void 

Backoff::IncrNumRetries (void) 

{

  m_numBackoffRetries++;

}

int64_t

Backoff::AssignStreams (int64_t stream)

{

  NS_LOG_FUNCTION (this << stream);

  m_rng->SetStream (stream);

  return 1;

}

} // namespace ns3