adaptive_skip.C

/*
 * This file is part of the "Archon" framework.
 * (http://files3d.sourceforge.net)
 *
 * Copyright © 2002 by Kristian Spangsege and Brian Kristiansen.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation under the terms of the GNU General Public License is
 * hereby granted. No representations are made about the suitability of
 * this software for any purpose. It is provided "as is" without express
 * or implied warranty. See the GNU General Public License
 * (http://www.gnu.org/copyleft/gpl.html) for more details.
 *
 * The characters in this file are ISO8859-1 encoded.
 *
 * The documentation in this file is in "Doxygen" style
 * (http://www.doxygen.org).
 */

// Unix headers
#include <sys/time.h>
#include <unistd.h>

// ANSI-C headers
#include <stdio.h>
#include <stdlib.h>

#include <archon/util/time.H>
#include <archon/util/adaptive_skip.H>


namespace Archon
{
  namespace Utilities
  {
    AdaptiveSkip::AdaptiveSkip(unsigned long millisBetweenOutTicks,
                               unsigned long checksPerOutTick):
      timeOfLastCheck(getTimeInMilliSeconds()),
      timeOfLastOutTick(timeOfLastCheck - millisBetweenOutTicks),
      millisBetweenOutTicks(millisBetweenOutTicks),
      checksPerOutTick(checksPerOutTick),
      skippedTicks(0),
      ticksPerCheck(1) {}

    unsigned long AdaptiveSkip::getTimeInMilliSeconds()
    {
      return Time::now().getMilliSeconds();
    }

    bool AdaptiveSkip::check()
    {
      // Estimate how many ticks to skip until next check
      const unsigned long now = getTimeInMilliSeconds();
      unsigned long timeSinceLastCheck = now - timeOfLastCheck;
      if(timeSinceLastCheck == 0) timeSinceLastCheck = 1;
      ticksPerCheck = int(double(ticksPerCheck) / timeSinceLastCheck *
                          millisBetweenOutTicks/checksPerOutTick);
      if(ticksPerCheck == 0) ticksPerCheck = 1;
      timeOfLastCheck = now;
      skippedTicks = 0;

      if(now - timeOfLastOutTick > millisBetweenOutTicks)
      {
        timeOfLastOutTick = now;
        return true;
      }

      return false;
    }
  }
}

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