packet-loss-counter.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 *  Copyright (c) 2009 INRIA, UDCAST
 *
 * 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: Amine Ismail <amine.ismail@sophia.inria.fr>
 *                      <amine.ismail@udcast.com>
 */

#include "ns3/log.h"
#include "ns3/simulator.h"
#include "ns3/uinteger.h"
#include "packet-loss-counter.h"

namespace ns3 {

NS_LOG_COMPONENT_DEFINE ("PacketLossCounter");

PacketLossCounter::PacketLossCounter (uint8_t bitmapSize)
  : m_lost (0),
    m_bitMapSize (0),
    m_lastMaxSeqNum (0),
    m_receiveBitMap (0)
{
  NS_LOG_FUNCTION (this << bitmapSize);
  SetBitMapSize (bitmapSize);
}

PacketLossCounter::~PacketLossCounter ()
{
  NS_LOG_FUNCTION (this);
  delete [] m_receiveBitMap;
}

uint16_t
PacketLossCounter::GetBitMapSize () const
{
  NS_LOG_FUNCTION (this);
  return m_bitMapSize * 8;
}

void
PacketLossCounter::SetBitMapSize (uint16_t winSize)
{
  NS_LOG_FUNCTION (this << winSize);

  NS_ASSERT_MSG (winSize%8==0,"The packet window size should be a multiple of 8");
  m_bitMapSize = winSize/8;
  if (m_receiveBitMap!=0)
    {
      delete [] m_receiveBitMap;
    }
  m_receiveBitMap = new uint8_t [m_bitMapSize] ();
  memset (m_receiveBitMap,0xFF,m_bitMapSize);
}

uint32_t
PacketLossCounter::GetLost () const
{
  NS_LOG_FUNCTION (this);
  return m_lost;
}

bool
PacketLossCounter::GetBit (uint32_t seqNum)
{
  NS_LOG_FUNCTION (this << seqNum);
  return ((m_receiveBitMap[(seqNum%(m_bitMapSize*8))/8] >> (7-(seqNum%8)))&0x01);
}

void
PacketLossCounter::SetBit (uint32_t seqNum, bool val)
{
  NS_LOG_FUNCTION (this << seqNum << val);
  if (val)
    {
      m_receiveBitMap[(seqNum%(m_bitMapSize*8))/8] |= 0x80 >> (seqNum%8);
    }
  else
    {
      m_receiveBitMap[(seqNum%(m_bitMapSize*8))/8] &= ~(0x80 >> (seqNum%8));
    }
}

/*
 * This algo works as follows:
 * When a packet is received:
 * 1) From the last received packet to the current one:
 *    1.1) check the corresponding bit in the bitMAP.
 *    This bit indicates if the packet with (SeqNum-bitMapSizeInBit) is
 *    received (1) or not (0)
 *    1.2) Mark the packet as lost (0) in the bitMap
 * 2) Mark the current packet as received (1) in the bitMap
 * 3) Update the value of the last received packet
 */

void
PacketLossCounter::NotifyReceived (uint32_t seqNum)
{
  NS_LOG_FUNCTION (this << seqNum);
  for (uint32_t i=m_lastMaxSeqNum+1; i<=seqNum; i++)
    {
      if (GetBit (i)!=1)
        {
          NS_LOG_INFO ("Packet lost: " << i-(m_bitMapSize*8));
          m_lost++;
        }
      SetBit (i, 0);
    }
  SetBit (seqNum, 1);
  if (seqNum>m_lastMaxSeqNum)
    {
      m_lastMaxSeqNum = seqNum;
    }
}

} // namespace ns3