CPU Load measurement for Windows, found on StackOverflow

WinCPULoad.cpp

#include <Windows.h>

static float CalculateCPULoad(unsigned long long idleTicks, unsigned long long totalTicks)
{
   static unsigned long long _previousTotalTicks = 0;
   static unsigned long long _previousIdleTicks = 0;

   unsigned long long totalTicksSinceLastTime = totalTicks-_previousTotalTicks;
   unsigned long long idleTicksSinceLastTime  = idleTicks-_previousIdleTicks;

   float ret = 1.0f-((totalTicksSinceLastTime > 0) ? ((float)idleTicksSinceLastTime)/totalTicksSinceLastTime : 0);

   _previousTotalTicks = totalTicks;
   _previousIdleTicks  = idleTicks;
   return ret;
}

static unsigned long long FileTimeToInt64(const FILETIME & ft) {return (((unsigned long long)(ft.dwHighDateTime))<<32)|((unsigned long long)ft.dwLowDateTime);}

// Returns 1.0f for "CPU fully pinned", 0.0f for "CPU idle", or somewhere in between
// You'll need to call this at regular intervals, since it measures the load between
// the previous call and the current one.  Returns -1.0 on error.
float GetCPULoad()
{
   FILETIME idleTime, kernelTime, userTime;
   return GetSystemTimes(&idleTime, &kernelTime, &userTime) ? CalculateCPULoad(FileTimeToInt64(idleTime), FileTimeToInt64(kernelTime)+FileTimeToInt64(userTime)) : -1.0f;
}