//Листинг 6.4. Тест для высокоточного измерения временного интервала

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
   PAINTSTRUCT ps;
   HDC hdc;

   TCHAR str [60], tmp[20];
   int i, sum;
   LARGE_INTEGER frequency, Start, End;
   static __int64 totalTime;
   switch (message)
   {
   case WM_COMMAND:
      switch (LOWORD(wParam))
      {
      case ID_CYCLE:
         QueryPerformanceFrequency(&frequency);
         Sleep(0);
         QueryPerformanceCounter(&Start);
         // Измеряемый код
         for (i = sum = 0; i < 1000; i++) sum += i;
         //////////////////////////////////////////
         QueryPerformanceCounter(&End);
         totalTime = (End.QuadPart - Start.QuadPart)*1000000/
			          frequency.QuadPart;
         InvalidateRect(hWnd, NULL, TRUE);
		 break;
      case IDM_EXIT: DestroyWindow(hWnd); break;
      default: return DefWindowProc(hWnd, message, wParam, lParam);
	  }
   break;
   case WM_PAINT:
      hdc = BeginPaint(hWnd, &ps);
      _tcscpy(str, _T("Время работы цикла в мкс: "));
	  _i64tot(totalTime, tmp, 10);
	  _tcscat(str, tmp);
      TextOut(hdc, 0, 0, str, _tcslen(str));
      EndPaint(hWnd, &ps);
	  break;
   case WM_DESTROY: PostQuitMessage(0); break;
   default: return DefWindowProc(hWnd, message, wParam, lParam);
   }
   return 0;
}