How to serialize a time_point?

[JUAN DENT]

Having this code:

namespace date
{
   using days = std::chrono::duration<int, std::ratio_multiply<std::ratio<24>, 
   std::chrono::hours::period>>;

   template <class Duration> 
   using sys_time =std::chrono::time_point<std::chrono::system_clock, Duration>;
   
   using sys_days = sys_time<days>;
}

I have a a sys_days stored in a database as an integer field. I need to transform int to sys_days and sys_days to int. The only problem is that sys_days (being a time_point) has its representation as a private _Duration.

date::sys_days int_to_sysdays(int val)
{
    date::sys_time<date::days> d = val;    // HOW???
    return d;
}

Regards,
Juan Dent

[poteto]

I haven't tested this but this should be the general idea.

serialize:
std::chrono::duration_cast<date::days>(std::chrono::system_clock::now() - tp.time_since_epoch()).count();

deserialize:
std::chrono::duration_cast<date::days>(tp.time_since_epoch() + date::days(val)).count();

[JUAN DENT]

In deserialize, where do we get tp from? The name of this function would be something like 'date::sys_days int_to_sysdays(int val)'

This does not work:

date::sys_days tp = std::chrono::duration_cast<date::days>(date::days(val)).count();

I get error:

error C2440: 'initializing': cannot convert from 'date::days' to 'std::chrono::time_point<std::chrono::system_clock,date::days>'

In serialize, where do we get tp from? The name of this function would be like 'int sysdays_to_int(date::sys_days days)'

std::chrono::duration_cast<date::days>(std::chrono::system_clock::now() - days.time_since_epoch()).count();

[poteto]

Yea I didn't know what I was writing.

.count should be returning an int, I believe.

I actually tested this for once.

int main()
{
    int i = std::chrono::duration_cast<date::days>(std::chrono::system_clock::now().time_since_epoch()).count();

    std::chrono::system_clock::time_point tp(date::days(i));
  std::cout << "Hello, " << std::chrono::duration_cast<date::days>(date::days(i)).count() << "!\n";
}

[JUAN DENT]

Hi poteto,

I got the first code correct:

int sysdays_to_int(date::sys_days days)
{
		int i = std::chrono::duration_cast<date::days>(days.time_since_epoch()).count();
		return i;
}

but the other conversion function is still unknown to me:

date::sys_days int_to_sysdays(int val)
{
             /// ??????
}

Could you please help?

[JUAN DENT]

I think I got it:

date::sys_days int_to_sysdays(int val)
{
	std::chrono::time_point<std::chrono::system_clock, date::days> tp{};
	tp += date::days{ val };
	return tp;
}

Right?

Juan