Common.h File Reference

#include "Stroika/Foundation/StroikaPreComp.h"
#include <chrono>
#include <ctime>
#include "Common.inl"

Go to the source code of this file.

Namespaces
namespace	Stroika::Foundation

Functions
template<typename CLOCK_T , typename DURATION_T = typename CLOCK_T::duration>
auto	Stroika::Foundation::Time::Pin2SafeSeconds (const chrono::time_point< CLOCK_T, DURATION_T > &tp) -> chrono::time_point< CLOCK_T, DURATION_T >

Detailed Description

Note

Code-Status: Beta

Definition in file Foundation/Time/Common.h.

Function Documentation

Pin2SafeSeconds()

template<typename CLOCK_T , typename DURATION_T = typename CLOCK_T::duration>

auto Stroika::Foundation::Time::Pin2SafeSeconds

(

const chrono::time_point< CLOCK_T, DURATION_T > &

tp

)

-> chrono::time_point<CLOCK_T, DURATION_T>

Note

Design Note About time_t

This is generally a 64-bit (but sometimes, like for 32-bit AIX, its 32-bit) signed (but not guaranteed signed) quantity. It generally represents a number of seconds since midnight Jan 1, 1970 in UTC.

From http://en.cppreference.com/w/cpp/chrono/c/time_t Arithmetic type capable of representing times.

Although not defined, this is almost always an integral value holding the number of seconds (not counting leap seconds) since 00:00, Jan 1 1970 UTC, corresponding to POSIX time.

Because of this, basically ALL the Stroika APIs (unless an obvious or stated exception) treat time_t as in UTC.

The Stroika APIs do NOT assume 64-bit, nor signedness, but when we require signedness, we use make_signed_t<time_t> Several APIs internally (or explicitly) use duration_cast, and frequently those APIs do duration_cast to chrono::seconds.

https://en.cppreference.com/w/cpp/chrono/duration/duration_cast Casting from a floating-point duration to an integer duration is subject to undefined behavior when the floating-point value is NaN, infinity, or too large to be representable by the target's integer type. Otherwise, casting to an integer duration is subject to truncation as with any static_cast to an integer type.

In particular, Stroika makes use of INF values (Time::kInfinity) for durations because it so easily works with TimePoints and adding etc.

But - we must be careful when calling std c++ APIs (like timed_mutex::wait_until()) to provide conforming timepoint values (even though https://en.cppreference.com/w/cpp/thread/condition_variable/wait_until says nothing about passing in inf floating point values).

With Ubuntu 22.04, ubsan on clang++15 and libc++ seem to require this safety check.

Definition at line 8 of file Foundation/Time/Common.inl.