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

/*

 * Copyright (c) 2005 INRIA

 *

 * 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: Mathieu Lacage <mathieu.lacage.inria.fr>

 */

#include "system-wall-clock-ms.h"

#include "abort.h"

#include <sys/times.h>

namespace ns3 {

class SystemWallClockMsPrivate {

public:

  void Start (void);

  int64_t End (void);

  int64_t GetElapsedReal (void) const;

  int64_t GetElapsedUser (void) const;

  int64_t GetElapsedSystem (void) const;

private:

  struct tms m_startTimes;

  clock_t m_startTime;

  int64_t m_elapsedReal;

  int64_t m_elapsedUser;

  int64_t m_elapsedSystem;

};

void 

SystemWallClockMsPrivate::Start (void)

{

  m_startTime = times (&m_startTimes);

}

int64_t

SystemWallClockMsPrivate::End (void)

{

  //

  // We need to return the number of milliseconds that have elapsed in some

  // reasonably portable way.  The underlying function that we will use returns

  // a number of elapsed ticks.  We can look up the number of ticks per second

  // from the system configuration.

  //

  // Conceptually, we need to find the number of elapsed clock ticks and then

  // multiply the result by the milliseconds per clock tick (or divide by clock

  // ticks per millisecond).  Integer dividing by clock ticks per millisecond

  // is bad since this number is fractional on most machines and would result

  // in divide by zero errors due to integer rounding.

  //

  // Multiplying by milliseconds per clock tick works up to a clock resolution 

  // of 1000 ticks per second.  If we go  past this point, we begin to get zero

  // elapsed times when millisecondsPerTick becomes fractional and another 

  // rounding error appears.

  //

  // So rounding errors using integers can bite you from both direction.  Since 

  // all of our targets have math coprocessors, why not just use doubles 

  // internally?  Works fine, lasts a long time.

  //

  // If millisecondsPerTick becomes fractional, and an elapsed time greater than 

  // a milliscond is measured, the function will work as expected.  If an elapsed 

  // time is measured that turns out to be less than a millisecond, we'll just 

  // return zero which would, I think, also will be expected.

  //

  static int64_t ticksPerSecond = sysconf (_SC_CLK_TCK);

  static double millisecondsPerTick = 1000. / ticksPerSecond;

  //

  // If sysconf () fails, we have no idea how to do the required conversion to ms.

  //

  NS_ABORT_MSG_IF (ticksPerSecond == -1, "SystemWallClockMsPrivate(): Cannot sysconf (_SC_CLK_TCK)");

  struct tms endTimes;

  clock_t endTime = times (&endTimes);

  double tmp;

  tmp = static_cast<double> (endTime - m_startTime) * millisecondsPerTick;

  m_elapsedReal = static_cast<int64_t> (tmp);

  tmp = static_cast<double> (endTimes.tms_utime - m_startTimes.tms_utime) * millisecondsPerTick;

  m_elapsedUser = static_cast<int64_t> (tmp);

  tmp = static_cast<double> (endTimes.tms_stime - m_startTimes.tms_stime) * millisecondsPerTick;

  m_elapsedSystem = static_cast<int64_t> (tmp);

  return m_elapsedReal;

}

int64_t

SystemWallClockMsPrivate::GetElapsedReal (void) const

{

  return m_elapsedReal;

}

int64_t

SystemWallClockMsPrivate::GetElapsedUser (void) const

{

  return m_elapsedUser;

}

int64_t

SystemWallClockMsPrivate::GetElapsedSystem (void) const

{

  return m_elapsedSystem;

}

SystemWallClockMs::SystemWallClockMs ()

  : m_priv (new SystemWallClockMsPrivate ())

SystemWallClockMs::~SystemWallClockMs ()

{

  delete m_priv;

  m_priv = 0;

}

void

SystemWallClockMs::Start (void)

{

  m_priv->Start ();

}

int64_t

SystemWallClockMs::End (void)

{

  return m_priv->End ();

}

int64_t

SystemWallClockMs::GetElapsedReal (void) const

{

  return m_priv->GetElapsedReal ();

}

int64_t

SystemWallClockMs::GetElapsedUser (void) const

{

  return m_priv->GetElapsedUser ();

}

int64_t

SystemWallClockMs::GetElapsedSystem (void) const

{

  return m_priv->GetElapsedSystem ();

}

}; // namespace ns3