A High-Resolution Timer for Win32

This post lists the code for creating a high resolution timer for the Microsoft Windows platform. High resolution timers are often used in multimedia and entertainment applications for timing events up to the microsecond.

This is a heavily modified re-post of the article that used to be on the Scriptionary.com website before the change to the blog, read the source code for details.

#ifndef _TIMER_H_
#define _TIMER_H_

#ifndef WIN32_LEAN_AND_MEAN
#  define WIN32_LEAN_AND_MEAN
#endif

#include <windows.h>

// Defines a simple High Resolution Timer
class Timer
{
public:
  // Construct the timer and initialize all of the
  // members by resetting them to their zero-values.
  Timer(void) {
    Reset();
  }

  ~Timer(void){ /* empty */ }

  // Activate the timer and poll the counter.
  void Start(void) {
    _Active = true;
    PollCounter(_StartCount);
  }

  // Deactivate the timer and poll the counter.
  void Stop(void) {
    _Active = false;
    PollCounter(_EndCount);
  }

  // Stops the timer if it's active and resets all
  // of the Timer's members to their initial values.
  void Reset(void) {
    if (_Active)
      Stop();

    QueryPerformanceFrequency(&_Frequency);

    _StartTime = (_EndTime = 0.0);
    _StartCount.QuadPart = (_EndCount.QuadPart = 0);
    _Active = false;
  }

  // Returns the time elapsed since Start() was called
  // in micro-seconds
  const long double GetTimeInMicroSeconds(void) {
    const long double MicroFreq =
      1000000.0 / _Frequency.QuadPart;

    if (_Active)
      PollCounter(_EndCount);

    _StartTime = _StartCount.QuadPart * MicroFreq;
    _EndTime = _EndCount.QuadPart * MicroFreq;

    return _EndTime - _StartTime;
  }

  // Returns the time elapsed since Start() was called
  // in milli-seconds
  const long double GetTimeInMilliseconds(void) {
    return GetTimeInMicroSeconds() * 0.001;
  }

  // Returns the time elapsed since Start() was called
  // in seconds
  const long double GetTimeInSeconds( void ) {
    return GetTimeInMicroSeconds() * 0.000001;
  }

  // Returns TRUE if the Timer is currently active
  const bool IsActive(void) const {
    return _Active;
  }
private:
  // Poll the query performance counter, safely by tying
  // the polling functionality temporarily to a single
  // logical processor (identified by 0).
  void PollCounter(LARGE_INTEGER& Out) {
    HANDLE Thread = GetCurrentThread();

    DWORD_PTR OldMask = SetThreadAffinityMask(Thread, 0);
      QueryPerformanceCounter(&Out);
    SetThreadAffinityMask(Thread, OldMask);
  }

private:
  bool _Active;
  long double
    _StartTime,
    _EndTime;
  LARGE_INTEGER
    _Frequency,
    _StartCount,
    _EndCount;
}; // class Timer

#endif

Here’s an incredibly simple example of how you could potentially use the class:

int main( int argc, const char* argv[] )
{
  Timer myTime;

  std::cout << "Starting the Timer..." << std::endl;
  MyTime.Start();

  std::cout << "Going to sleep for 5 seconds." << std::endl;
  Sleep(5000); // or something else for a while

  std::cout << "Stopping the Timer." << std::endl;
  MyTime.Stop();

  std::cout << MyTime.GetTimeInSeconds()
    << " seconds passed" << std::endl;

  return 0;
}