C / C++ / MFC

LARGE_INTEGER freq;
QueryPerformanceFrequency(&freq);

int const delay_ms = 500; // the delay you need, in milliseconds

long long n = delay_ms * freq.QuadPart / 1000;

LARGE_INTEGER c;
QueryPerformanceCounter(&c);

long long const f = c.QuadPart + n;

do
{
   QueryPerformanceCounter(&c);
} while( c.QuadPart < f);

Sharath86 wrote:

can anyone please give me some easy to understand code to do this replacement.

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

Sharath86 wrote:

btw not in an MFC application...

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

TechyMaila wrote:

Which is a better way to return values and why?

int Test(int n)
{
if(n==0 || n==1)
  return n;
return -1; 
}

inline int Test(int n)
{
   return (n == 0 || n == 1) ? n : -1;
}

Viorel. wrote:

return (n == 0 || n == 1) ? n : -1;

Maxwell Chen wrote:

?: operator is slow.

int TestI(int n)
{
	if(n==0 || n==1)
		return n;
	return -1;
}

int TestO(int n)
{
	return (n == 0 || n == 1) ? n : -1;
}

void CTestDlg::OnBnClickedButton1()
{
	DWORD s = GetTickCount();
	for(UINT i = 0; i < 0xE00000; i++)
	{
		TestI(3);
	}
	DWORD e = GetTickCount();
	DWORD d = e - s;
	CString t;
	t.Format("Time 0x%X", d);
	AfxMessageBox(t);
}

void CTestDlg::OnBnClickedButton2()
{
	DWORD s = GetTickCount();
	for(UINT i = 0; i < 0xE00000; i++)
	{
		TestO(3);
	}
	DWORD e = GetTickCount();
	DWORD d = e - s;
	CString t;
	t.Format("Time 0x%X", d);
	AfxMessageBox(t);
}

If-Else:
0xDC, 0xDC, 0xEC, 0xF0, 0xDC

? : operator:
0xFE, 0xF0, 0xFA, 0xF1, 0xFE

int __declspec(noinline) TestI(int n)
{
    volatile static int k = n; // prevents removing of calls
    if(n==0 || n==1)
        return n;
    return -1;
}

int __declspec(noinline) TestO(int n)
{
    volatile static int k = n; // prevents removing of calls
    return (n == 0 || n == 1) ? n : -1;
}

void main()
{
    const long N = 1000000000L;
    DWORD s = ::GetTickCount();
    for(long i = 0; i < N; ++i)
    {
        TestI(3); 
    }
    DWORD t = ::GetTickCount() - s;
    printf("%i\n", t);
    s = ::GetTickCount();
    for(long i = 0; i < N; ++i) 
    { 
        TestO(3); 
    }
    t = ::GetTickCount() - s;
    printf("%i\n", t);
}

9754 (if-else) (ignored, warm-up exercise)
9323 (? : ) (ignored, warm-up exercise)
9223 (if-else)
9214 (? : )

?TestI@@YAHH@Z PROC					; TestI, COMDAT

; 5    : 	volatile static int k = n; // prevents removing of calls    

	mov	eax, 1
	test	BYTE PTR ?$S1@?1??TestI@@YAHH@Z@4IA, al
	jne	SHORT $LN8@TestI
	or	DWORD PTR ?$S1@?1??TestI@@YAHH@Z@4IA, eax
	mov	DWORD PTR ?k@?1??TestI@@YAHH@Z@4HC, 3
$LN8@TestI:

; 6    : 	if(n==0 || n==1)
; 7    : 		return n;
; 8    : 	return -1;

	or	eax, -1

; 9    : }

	ret	0
?TestI@@YAHH@Z ENDP					; TestI

?TestO@@YAHH@Z PROC					; TestO, COMDAT

; 13   : 	volatile static int k = n; // prevents removing of calls    

	mov	eax, 1
	test	BYTE PTR ?$S2@?1??TestO@@YAHH@Z@4IA, al
	jne	SHORT $LN8@TestO
	or	DWORD PTR ?$S2@?1??TestO@@YAHH@Z@4IA, eax
	mov	DWORD PTR ?k@?1??TestO@@YAHH@Z@4HC, 3
$LN8@TestO:

; 14   : 	return (n == 0 || n == 1) ? n : -1;

	or	eax, -1

; 15   : }

	ret	0
?TestO@@YAHH@Z ENDP					; TestO

Viorel. wrote:

it seems that this compiler generates good enough code for both cases.

<br />
int Test(int n)<br />
{<br />
int nReturn = 0 ;<br />
switch(n)<br />
  {<br />
  case 0:<br />
  case 1:<br />
     nReturn=1;<br />
    break;<br />
  default:<br />
    nReturn=-1;<br />
    break;<br />
  }<br />
	return nReturn;<br />
}<br />