time.cpp File Reference

#include <corecrt_internal_time.h>

Include dependency graph for time.cpp:

Go to the source code of this file.

Typedefs
using	get_system_time_function_type = void(WINAPI *)(LPFILETIME)

Functions
template<get_system_time_function_type GetSystemTimeFunction, typename TimeSpecType >
	_Success_ (return !=0) static int __cdecl common_timespec_get(TimeSpecType *const ts
int const base	throw ()
int __cdecl	_timespec32_get (_timespec32 *const ts, int const base)
int __cdecl	_timespec64_get (_timespec64 *const ts, int const base)
template<typename TimeType >
static TimeType __cdecl	common_time (TimeType *const result) throw ()
__time32_t __cdecl	_time32 (__time32_t *const result)
__time64_t __cdecl	_time64 (__time64_t *const result)

Typedef Documentation

get_system_time_function_type

using get_system_time_function_type = void(WINAPI *)(LPFILETIME)

Definition at line 12 of file time.cpp.

Function Documentation

_Success_()

template<get_system_time_function_type GetSystemTimeFunction, typename TimeSpecType >

_Success_

(

return !

= 0

)

const

_time32()

__time32_t __cdecl _time32

(

__time32_t *const

result

)

Definition at line 94 of file time.cpp.

{
    return common_time(result);
}

_time64()

__time64_t __cdecl _time64

(

__time64_t *const

result

)

Definition at line 99 of file time.cpp.

{
    return common_time(result);
}

_timespec32_get()

int __cdecl _timespec32_get	(	_timespec32 *const	ts,
		int const	base
	)

Definition at line 48 of file time.cpp.

{
    return common_timespec_get<__acrt_GetSystemTimePreciseAsFileTime>(ts, base);
}

_timespec64_get()

int __cdecl _timespec64_get	(	_timespec64 *const	ts,
		int const	base
	)

Definition at line 53 of file time.cpp.

{
    return common_timespec_get<__acrt_GetSystemTimePreciseAsFileTime>(ts, base);
}

Referenced by timespec_get().

common_time()

template<typename TimeType >

static TimeType __cdecl common_time ( TimeType *const  result ) throw ( )

static

Definition at line 64 of file time.cpp.

{
    typedef __crt_time_time_t_traits<TimeType> time_traits;
 
    typename time_traits::timespec_type ts{};
 
    // The resolution of time() is in seconds, so we can afford to use
    // a less precise, but faster method of getting the time.
    // GetSystemTimePreciseAsFileTime uses QueryPerformanceCounter which
    // needs to be virtualized on some systems in order to be accurate, which can
    // be significantly slower than calling GetSystemTimeAsFileTime.
    // For example, hypervisors will virtualize QPC calls in order to take into
    // account virtual machine live migration.
    // Note that calling the less precise API is still observable because the tick
    // count may update +/- 15ms, but this should not affect common use of time().
    // See https://docs.microsoft.com/en-us/windows/desktop/sysinfo/acquiring-high-resolution-time-stamps
    // for more details.
    if (common_timespec_get<GetSystemTimeAsFileTime>(&ts, TIME_UTC) != TIME_UTC)
    {
        ts.tv_sec = static_cast<TimeType>(-1);
    }
 
    if (result)
    {
        *result = ts.tv_sec;
    }
 
    return ts.tv_sec;
}

Referenced by _time32(), and _time64().

throw()

int const base throw

(

)

Definition at line 16 of file time.cpp.

{
    typedef decltype(ts->tv_sec)                time_type;
    typedef __crt_time_time_t_traits<time_type> time_traits;
 
    _VALIDATE_RETURN(ts != nullptr, EINVAL, 0);
 
    if (base != TIME_UTC)
    {
        return 0;
    }
 
    __crt_filetime_union system_time{};
    GetSystemTimeFunction(&system_time._filetime);
 
    __time64_t const filetime_scale{10 * 1000 * 1000}; // 100ns units
 
    __time64_t const epoch_time{static_cast<__time64_t>(system_time._scalar) - _EPOCH_BIAS};
 
    __time64_t const seconds    {epoch_time / filetime_scale};
    __time64_t const nanoseconds{epoch_time % filetime_scale * 100};
 
    if (seconds > static_cast<__time64_t>(time_traits::max_time_t))
    {
        return 0;
    }
 
    ts->tv_sec  = static_cast<time_type>(seconds);
    ts->tv_nsec = static_cast<long>(nanoseconds);
    return base;
}