LARGE_INTEGER lastTime;
LARGE_INTEGER tickFreq;
int ready = 0;

//QueryPerformanceCounter(&time);
//QueryPerformanceFrequency(&rate);
//double calc = (double) time.QuadPart / (double)rate.QuadPart;

void timerPrep(void)
{
	QueryPerformanceFrequency(&tickFreq);
	QueryPerformanceCounter(&lastTime);
	ready = 1;
}

double timerTick(void)
{
	if(ready == 0) {return 0;}

	LARGE_INTEGER thisTime;
	double theDifference;

	QueryPerformanceCounter(&thisTime);
	theDifference = ((double)thisTime.QuadPart - (double)lastTime.QuadPart) * tickFreq.QuadPart;

	lastTime = thisTime;

	return theDifference;	
}

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

LARGE_INTEGER lastTime;
LARGE_INTEGER tickFreq;
int ready = 0;

//QueryPerformanceCounter(&time);
//QueryPerformanceFrequency(&rate);
//double calc = (double) time.QuadPart / (double)rate.QuadPart;

void timerPrep(void)
{
	QueryPerformanceFrequency(&tickFreq);
	QueryPerformanceCounter(&lastTime);
	ready = 1;
}

double timerTick(void)
{
	if(ready == 0) {return 0;}

	LARGE_INTEGER thisTime;
	double theDifference;

	QueryPerformanceCounter(&thisTime);
	theDifference = ((double)thisTime.QuadPart - (double)lastTime.QuadPart) * tickFreq.QuadPart;

	lastTime = thisTime;

	return theDifference;	
}


int main(int argc, char *argv[])
{

  timerPrep();
  
  /*int i = 0;
  for (i = 0; i < 1000; ++i)
  {
    int lala = 4009;
    int boo = i / lala;
  }*/

  system("PAUSE");

  printf("Took %i\n", timerTick());

  printf("laaaa\n");
  system("PAUSE");
  return 0;
}

Quote:Original post by xyuri
Having lost all my source code in a recent hard disk format I dont have my good ole performance timer that I've used in previous little games, so I'm back on the web looking it all up and rebuilding the functions.

Anyways, I have the following basic code to record time differences, but near the beginning it sometimes gives negative numbers, why?

<code snip>

I have written this basic console app to do some rough testing

*** Source Snippet Removed ***

Resources on the web on how to use these functions seem rather vague ... does anyone know what I'm doing wrong at a glance?

  double timerTick(void)  ...  printf("Took %i\n", timerTick());

  theDifference = ((double)thisTime.QuadPart - (double)lastTime.QuadPart) / double(tickFreq.QuadPart);

Quote:Original post by Anonymous Poster
don't use LARGE_INTEGER, you can use __int64s with those functions. then take difference between __int64s and convert to double, then divide by the frequency.

QueryPerformanceCounter((LARGE_INTEGER *)&my_i64_var);

Quote:Original post by Emmanuel Deloget

Quote:Original post by Anonymous Poster
don't use LARGE_INTEGER, you can use __int64s with those functions. then take difference between __int64s and convert to double, then divide by the frequency.

Well, LARGE_INTEGER is the type which is used by QPC and QFF. Since this is a type abstraction (we don't have to worry about the underlying data type), I believe we should still use them.

QueryPerformanceCounter((LARGE_INTEGER *)&my_i64_var);

Is probably more dangerous, and I'm not sure it is really needed.

Regards,

typedef __int64 LONGLONG;#if defined(MIDL_PASS)typedef struct _LARGE_INTEGER {#else // MIDL_PASStypedef union _LARGE_INTEGER {    struct {        DWORD LowPart;        LONG HighPart;    };    struct {        DWORD LowPart;        LONG HighPart;    } u;#endif //MIDL_PASS    LONGLONG QuadPart;} LARGE_INTEGER;

Quote:Original post by ZedFx
Taken from the windows header files

*** Source Snippet Removed ***

as you can see __int64 is the same as LARGE_INTEGER

Quote:Original post by ZedFx
so why use __int64 ?
-> because MSVC++ 7 has built in support for __int64
what does this mean ?
-> it means we can multiply and divide it safely in the function I detailed above
what if I dont have MSVC++ 7
-> then it is not necessary to use __int64, but you will have to implement the division and multiplication yourself

LARGE_INTEGER timerLast;LARGE_INTEGER timerThis;LARGE_INTEGER timerFreq;int timerReady = 0;void timerPrep(void){	QueryPerformanceFrequency(&timerFreq);	QueryPerformanceCounter(&timerThis);	timerReady = 1;}double timerTick(void){	// If timerPrep function hasnt been run then return 0	if(timerReady == 0) {return 0;}	// LAST = THIS so that THIS can be updated and the difference returned	timerLast = timerThis;	// Update THIS	QueryPerformanceCounter(&timerThis);	// Return the Difference	return (double)(timerThis.QuadPart - timerLast.QuadPart) / (double)timerFreq.QuadPart;}