Equivalent of gettimeday() for Windows

Question

Does anyone know an equivalent function of the gettimeofday() function in Windows environment? I am comparing a code execution time in Linux vs Windows. I am us

Answer 1

GetLocalTime() for the time in the system timezone, GetSystemTime() for UTC. If you want a seconds-since-epoch time, use SystemTimeToFileTime() or GetSystemTimeAsFileTime().

For interval taking, use GetTickCount(). It returns milliseconds since startup.

For taking intervals with the best possible resolution (limited by hardware only), use QueryPerformanceCounter().

Answer 2

Nowadys I would use the following for gettimeofday() on Windows, which is using GetSystemTimePreciseAsFileTime() if compiled for Windows 8 or higher and GetSystemTimeAsFileTime() otherwise:

#include <Windows.h>
struct timezone {
    int tz_minuteswest;
    int tz_dsttime;
};

int gettimeofday(struct timeval *tv, struct timezone *tz)
{
    if (tv) {
        FILETIME               filetime; /* 64-bit value representing the number of 100-nanosecond intervals since January 1, 1601 00:00 UTC */
        ULARGE_INTEGER         x;
        ULONGLONG              usec;
        static const ULONGLONG epoch_offset_us = 11644473600000000ULL; /* microseconds betweeen Jan 1,1601 and Jan 1,1970 */

#if _WIN32_WINNT >= _WIN32_WINNT_WIN8
        GetSystemTimePreciseAsFileTime(&filetime);
#else
        GetSystemTimeAsFileTime(&filetime);
#endif
        x.LowPart =  filetime.dwLowDateTime;
        x.HighPart = filetime.dwHighDateTime;
        usec = x.QuadPart / 10  -  epoch_offset_us;
        tv->tv_sec  = (time_t)(usec / 1000000ULL);
        tv->tv_usec = (long)(usec % 1000000ULL);
    }
    if (tz) {
        TIME_ZONE_INFORMATION timezone;
        GetTimeZoneInformation(&timezone);
        tz->tz_minuteswest = timezone.Bias;
        tz->tz_dsttime = 0;
    }
    return 0;
}

Answer 3

Here is a free implementation:

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <stdint.h> // portable: uint64_t   MSVC: __int64 

// MSVC defines this in winsock2.h!?
typedef struct timeval {
    long tv_sec;
    long tv_usec;
} timeval;

int gettimeofday(struct timeval * tp, struct timezone * tzp)
{
    // Note: some broken versions only have 8 trailing zero's, the correct epoch has 9 trailing zero's
    // This magic number is the number of 100 nanosecond intervals since January 1, 1601 (UTC)
    // until 00:00:00 January 1, 1970 
    static const uint64_t EPOCH = ((uint64_t) 116444736000000000ULL);

    SYSTEMTIME  system_time;
    FILETIME    file_time;
    uint64_t    time;

    GetSystemTime( &system_time );
    SystemTimeToFileTime( &system_time, &file_time );
    time =  ((uint64_t)file_time.dwLowDateTime )      ;
    time += ((uint64_t)file_time.dwHighDateTime) << 32;

    tp->tv_sec  = (long) ((time - EPOCH) / 10000000L);
    tp->tv_usec = (long) (system_time.wMilliseconds * 1000);
    return 0;
}

Answer 4

If you really want a Windows gettimeofday() implementation, here is one from PostgreSQL that uses Windows APIs and the proper conversions.

However if you want to time code, I suggest you look into QueryPerformanceCounter() or by directly invoking the TSC if you're only going to run on x86 for example.

Answer 5

This is the version of c++11 that uses chrono.

Thank you, Howard Hinnant for advice.

#if defined(_WIN32)
#include <chrono>

int gettimeofday(struct timeval* tp, struct timezone* tzp) {
  namespace sc = std::chrono;
  sc::system_clock::duration d = sc::system_clock::now().time_since_epoch();
  sc::seconds s = sc::duration_cast<sc::seconds>(d);
  tp->tv_sec = s.count();
  tp->tv_usec = sc::duration_cast<sc::microseconds>(d - s).count();

  return 0;
}

#endif // _WIN32