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 using MS Visual Studio 2010 and it keeps saying, identifier "gettimeofday" is undefined.

Answer 1

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 2

GetLocalTime() for the time in the system timezone, GetSystemTime() for UTC. Those return the date/time in a SYSTEMTIME structure, where it's parsed into year, month, etc. If you want a seconds-since-epoch time, use SystemTimeToFileTime() or GetSystemTimeAsFileTime(). The FILETIME is a 64-bit value with the number of 100ns intervals since Jan 1, 1601 UTC.

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

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