CPU usage (C, Windows XP)

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This program is a code dump.
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Minimum required version of Windows: 

- WinXP SP1

This code sample will output the current CPU usage in percent where 100% means max usage.

Known bugs: None 

<<cpuusage.c>>=
#include <windows.h>
#include <stdio.h>
//------------------------------------------------------------------------------------------------------------------
// Prototype(s)...
//------------------------------------------------------------------------------------------------------------------
CHAR cpuusage(void);
//-----------------------------------------------------
typedef BOOL ( __stdcall * pfnGetSystemTimes)( LPFILETIME lpIdleTime, LPFILETIME lpKernelTime, LPFILETIME lpUserTime );
static pfnGetSystemTimes s_pfnGetSystemTimes = NULL;
static HMODULE s_hKernel = NULL;
//-----------------------------------------------------
void GetSystemTimesAddress()
{
	if( s_hKernel == NULL )
	{   
		s_hKernel = LoadLibrary( "Kernel32.dll" );
		if( s_hKernel != NULL )
		{
			s_pfnGetSystemTimes = (pfnGetSystemTimes)GetProcAddress( s_hKernel, "GetSystemTimes" );
			if( s_pfnGetSystemTimes == NULL )
			{
				FreeLibrary( s_hKernel ); s_hKernel = NULL;
			}
		}
	}
}
//----------------------------------------------------------------------------------------------------------------
//----------------------------------------------------------------------------------------------------------------
// cpuusage(void)
// ==============
// Return a CHAR value in the range 0 - 100 representing actual CPU usage in percent.
//----------------------------------------------------------------------------------------------------------------
CHAR cpuusage()
{
	FILETIME               ft_sys_idle;
	FILETIME               ft_sys_kernel;
	FILETIME               ft_sys_user;
	ULARGE_INTEGER         ul_sys_idle;
	ULARGE_INTEGER         ul_sys_kernel;
	ULARGE_INTEGER         ul_sys_user;
	static ULARGE_INTEGER	 ul_sys_idle_old;
	static ULARGE_INTEGER  ul_sys_kernel_old;
	static ULARGE_INTEGER  ul_sys_user_old;
	CHAR  usage = 0;
	// we cannot directly use GetSystemTimes on C language
	/* add this line :: pfnGetSystemTimes */
	s_pfnGetSystemTimes(&ft_sys_idle,    /* System idle time */
		&ft_sys_kernel,  /* system kernel time */
		&ft_sys_user);   /* System user time */
	CopyMemory(&ul_sys_idle  , &ft_sys_idle  , sizeof(FILETIME)); // Could been optimized away...
	CopyMemory(&ul_sys_kernel, &ft_sys_kernel, sizeof(FILETIME)); // Could been optimized away...
	CopyMemory(&ul_sys_user  , &ft_sys_user  , sizeof(FILETIME)); // Could been optimized away...
	usage  =
		(
		(
		(
		(
		(ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
		(ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
		)
		-
		(ul_sys_idle.QuadPart-ul_sys_idle_old.QuadPart)
		)
		*
		(100)
		)
		/
		(
		(ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
		(ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
		)
		);
	ul_sys_idle_old.QuadPart   = ul_sys_idle.QuadPart;
	ul_sys_user_old.QuadPart   = ul_sys_user.QuadPart;
	ul_sys_kernel_old.QuadPart = ul_sys_kernel.QuadPart;
	return usage;
}
//------------------------------------------------------------------------------------------------------------------
// Entry point
//------------------------------------------------------------------------------------------------------------------
int main(void)
{
	int n;
	GetSystemTimesAddress();
	for(n=0;n<20;n++)
	{
		printf("CPU Usage: %3d%%\r",cpuusage());
		Sleep(200);
	}
	printf("\n");
	return 0;
}
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