void GetHighResUtcTime(FILETIME *ft) static GetSystemTimePreciseAsFileTimePtr pFunc = NULL; static HMODULE hKernel32 = NULL;
#include <windows.h> typedef VOID (WINAPI *GetSystemTimePreciseAsFileTimePtr)(LPFILETIME lpSystemTimeAsFileTime);
If you’ve ever needed to measure short time intervals (like benchmarking code, network latency, or frame timing) on Windows, you know the journey: GetTickCount , QueryPerformanceCounter , GetSystemTimeAsFileTime ... and then there's GetSystemTimePreciseAsFileTime . getsystemtimepreciseasfiletime windows 7
Or did it?
if (pFunc) pFunc(ft); // Windows 8+ or lucky Win7 else GetSystemTimeAsFileTime(ft); // Fallback for Windows 7 if (pFunc) pFunc(ft); // Windows 8+ or lucky
GetSystemTimePreciseAsFileTime does one beautiful thing: It reads the from the underlying hardware (HPET or TSC) and converts it to UTC. On supported systems, it offers microsecond-level precision (though not necessarily accuracy—that’s a topic for another day). The Windows 7 Reality When Microsoft released the Platform Update for Windows 7 (KB2670838), they quietly back-ported several newer APIs. For a while, developers noticed that GetSystemTimePreciseAsFileTime existed on some Windows 7 boxes.
This function is the gold standard for getting the current UTC time with high precision (microseconds/milliseconds) on modern Windows. But here’s the kicker: . if (!pFunc) hKernel32 = GetModuleHandleA("kernel32.dll")
if (!pFunc) hKernel32 = GetModuleHandleA("kernel32.dll"); pFunc = (GetSystemTimePreciseAsFileTimePtr) GetProcAddress(hKernel32, "GetSystemTimePreciseAsFileTime");