#include <stdlib.h>
#include <stdio.h>
#include <windows.h>
#include <ntdef.h>
#include <Mmsystem.h> // Library: Winmm.lib.

// gcc clockres.c  -l winmm -l ntdll

// http://www.sysinternals.com/Information/HighResolutionTimers.html
WINAPI NTSTATUS NtQueryTimerResolution (
    PULONG MinimumResolution,
    PULONG MaximumResolution,
    PULONG ActualResolution
);

// A side effect of this function is to synchronize the caller to a tick
DWORD get_timeGetTime_resolution() {
  DWORD time1, time2, priority;
  priority = GetThreadPriority (GetCurrentThread ());
  SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_TIME_CRITICAL);

  time1 = timeGetTime();
  do {
    time2 = timeGetTime();
  } while (time1 == time2);
  SetThreadPriority (GetCurrentThread (), priority);
  return time2 - time1;
}

DWORD get_NT_resolution() {
#ifndef Win9x
  DWORD res;
  ULONG MinRes, MaxRes, ActRes;
  res = NtQueryTimerResolution(&MinRes, &MaxRes, &ActRes);
  if (res) printf("NtStatus %lu\n", res);
  return ActRes;
#else
  return 0;
#endif
}
//----------------------------------------------------------------------
//
// Main
//
//----------------------------------------------------------------------
int main( int argc, char *argv[] )
{
   ULONG MinRes, MaxRes, ActRes;
   DWORD adjustment, clockInterval;
   BOOL  adjustmentDisabled;
   DWORD NtRes, TGTRes, Wait, NtResOld, TGTResOld, WaitOld;
   DWORD time1, time2, time3, time4;
   DWORD delay, resolution;
   DWORD res;
   MMRESULT mmres;
   int i, count;
   volatile int loop;
   const int delay_loop = 10000000;

   // Calibrate a random delay loop
   time1 = timeGetTime();
   time1 = timeGetTime();
   for (loop = 0; loop < delay_loop; loop++) {}
   time2 = timeGetTime();
   printf("Random delay value will be between 0 and %lu ms\n", time2 - time1);
   printf("Adjust so that it is greater than the resolution.\n");

   if (argc > 1)
      count = atoi(argv[1]);
   else
      count = 1;

   if (argc > 2)
      delay = atoi(argv[2]);
   else
      {
	 printf("Enter delay:\n");
	 while ((res = scanf("%lu", &delay)) != 1) {printf("%lu\n", res);};
      }

#ifndef Win9x
   res = NtQueryTimerResolution(&MinRes, &MaxRes, &ActRes);
   printf("NtStatus %lu; Min %lu Max %lu Act %lu x 100 ns\n", res, MinRes, MaxRes, ActRes);
#endif

   GetSystemTimeAdjustment( &adjustment,
			    &clockInterval,
			    &adjustmentDisabled );
   printf( "The system clock interval is %.06f ms\n",
	   (float) clockInterval / 10000 );


   // Make sure WaitFor is loaded.
   WaitForSingleObject(GetCurrentProcess(), 0);

   NtResOld = TGTResOld = WaitOld = 0;
   for (i = 0; i < count; i++)
      {
	 // Randomize time before calling WaitFor
	 for (loop = 0; loop < rand() % delay_loop; loop++) {}

	 time1 = timeGetTime();
	 res = WaitForSingleObject(GetCurrentProcess(), delay);
	 time2 = timeGetTime();
	 Wait = time2 - time1;

	 TGTRes = get_timeGetTime_resolution();
	 NtRes = get_NT_resolution();
	 if ((NtRes != NtResOld)
	     ||(TGTRes != TGTResOld)
	     ||(Wait != WaitOld))
	    {
	       if (delay > Wait)
		  printf("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\n");
	       printf("%d: Nt Res %lu, timeGetTime Res %lu, WaitFor Wait %lu\n",
		      i, NtRes, TGTRes, Wait);
	       NtResOld = NtRes;
	       TGTResOld = TGTRes;
	       WaitOld = Wait;
	    }

	 Sleep(950);
      }

   // Set the resolution and watch the effect
   if (argc > 3)
      resolution = atoi(argv[3]);
   else
      {
	 printf("Enter resolution:\n");
	 while (scanf("%lu", &resolution) != 1) {};
      }

   mmres = timeBeginPeriod(resolution);
   if (mmres != TIMERR_NOERROR)
      printf("timeBeginPeriod error %d\n", mmres);
   else
      printf("\ntimeBeginPeriod success\n");

   time3 = timeGetTime();
   res = WaitForSingleObject(GetCurrentProcess(), delay);
   time4 = timeGetTime();
   if (res != WAIT_TIMEOUT)
      printf("WaitForSingleObject error %lu\n", res);

#ifndef Win9x
   res = NtQueryTimerResolution(&MinRes, &MaxRes, &ActRes);
   printf("NtStatus %lu; Min %lu Max %lu Act %lu x 100 ns\n", res, MinRes, MaxRes, ActRes);
#endif

   GetSystemTimeAdjustment( &adjustment,
			    &clockInterval,
			    &adjustmentDisabled );
   printf( "The system clock interval is %.06f ms\n",
	   (float) clockInterval / 10000 );

   printf("timeGetTime resolution %lu\n", get_timeGetTime_resolution());

   printf("WaitFor Delay %lu, Wait %lu\n", delay, time4 - time3);
   exit(0);
}