[UCRT] Import Microsoft.Windows.SDK.CRTSource version 10.0.22621.3

Imported from https://www.nuget.org/packages/Microsoft.Windows.SDK.CRTSource/10.0.22621.3
License: MIT

sdk/lib/ucrt/time/time.cpp

@@ -0,0 +1,102 @@
+//
+// time.cpp
+//
+//      Copyright (c) Microsoft Corporation. All rights reserved.
+//
+// The timespec_get() and time() families of functions, which get the current
+// system time as a timespec and a time_t, respectively.
+//
+#include <corecrt_internal_time.h>
+
+
+using get_system_time_function_type = void(WINAPI *)(LPFILETIME);
+
+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()
+{
+    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;
+}
+
+extern "C" int __cdecl _timespec32_get(_timespec32* const ts, int const base)
+{
+    return common_timespec_get<__acrt_GetSystemTimePreciseAsFileTime>(ts, base);
+}
+
+extern "C" int __cdecl _timespec64_get(_timespec64* const ts, int const base)
+{
+    return common_timespec_get<__acrt_GetSystemTimePreciseAsFileTime>(ts, base);
+}
+
+
+
+// Gets the current system time and converts it to a time_t value. If 'result'
+// is non-null, the time is stored in '*result'.  The time is also returned
+// (even if 'result' is null).
+template <typename TimeType>
+static TimeType __cdecl common_time(TimeType* const result) throw()
+{
+    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;
+}
+
+extern "C" __time32_t __cdecl _time32(__time32_t* const result)
+{
+    return common_time(result);
+}
+
+extern "C" __time64_t __cdecl _time64(__time64_t* const result)
+{
+    return common_time(result);
+}