rate.cpp

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 * Author: Eitan Marder-Eppstein
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#include <ros/rate.h>

namespace ros
{

Rate::Rate(double frequency)
: start_(Time::now())
, expected_cycle_time_(1.0 / frequency)
, actual_cycle_time_(0.0)
{ }

Rate::Rate(const Duration& d)
  : start_(Time::now())
  , expected_cycle_time_(d.sec, d.nsec)
  , actual_cycle_time_(0.0)
{ }

bool Rate::sleep()
{
  Time expected_end = start_ + expected_cycle_time_;

  Time actual_end = Time::now();

  // detect backward jumps in time
  if (actual_end < start_)
  {
    expected_end = actual_end + expected_cycle_time_;
  }

  //calculate the time we'll sleep for
  Duration sleep_time = expected_end - actual_end;

  //set the actual amount of time the loop took in case the user wants to know
  actual_cycle_time_ = actual_end - start_;

  //make sure to reset our start time
  start_ = expected_end;

  //if we've taken too much time we won't sleep
  if(sleep_time <= Duration(0.0))
  {
    // if we've jumped forward in time, or the loop has taken more than a full extra
    // cycle, reset our cycle
    if (actual_end > expected_end + expected_cycle_time_)
    {
      start_ = actual_end;
    }
    // return false to show that the desired rate was not met
    return false;
  }

  return sleep_time.sleep();
}

void Rate::reset()
{
  start_ = Time::now();
}

Duration Rate::cycleTime() const
{
  return actual_cycle_time_;
}

WallRate::WallRate(double frequency)
: start_(WallTime::now())
, expected_cycle_time_(1.0 / frequency)
, actual_cycle_time_(0.0)
{}

WallRate::WallRate(const Duration& d)
: start_(WallTime::now())
, expected_cycle_time_(d.sec, d.nsec)
, actual_cycle_time_(0.0)
{}

bool WallRate::sleep()
{
  WallTime expected_end = start_ + expected_cycle_time_;

  WallTime actual_end = WallTime::now();

  // detect backward jumps in time
  if (actual_end < start_)
  {
    expected_end = actual_end + expected_cycle_time_;
  }

  //calculate the time we'll sleep for
  WallDuration sleep_time = expected_end - actual_end;

  //set the actual amount of time the loop took in case the user wants to know
  actual_cycle_time_ = actual_end - start_;

  //make sure to reset our start time
  start_ = expected_end;

  //if we've taken too much time we won't sleep
  if(sleep_time <= WallDuration(0.0))
  {
    // if we've jumped forward in time, or the loop has taken more than a full extra
    // cycle, reset our cycle
    if (actual_end > expected_end + expected_cycle_time_)
    {
      start_ = actual_end;
    }
    return false;
  }

  return sleep_time.sleep();
}

void WallRate::reset()
{
  start_ = WallTime::now();
}

WallDuration WallRate::cycleTime() const
{
  return actual_cycle_time_;
}

}