I need to convert std::chrono::time_point
to and from a long
type (integer 64 bits). I´m starting working with std::chrono
...
Here is my code:
int main ()
{
std::chrono::time_point<std::chrono::system_clock> now = std::chrono::system_clock::now();
auto epoch = now.time_since_epoch();
auto value = std::chrono::duration_cast<std::chrono::milliseconds>(epoch);
long duration = value.count();
std::chrono::duration<long> dur(duration);
std::chrono::time_point<std::chrono::system_clock> dt(dur);
if (dt != now)
std::cout << "Failure." << std::endl;
else
std::cout << "Success." << std::endl;
}
This code compiles, but does not show success.
Why is dt
different than now
at the end?
What is missing on that code?
as a single line:
long value_ms = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::time_point_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now()).time_since_epoch()).count();
I would also note there are two ways to get the number of ms in the time point. I'm not sure which one is better, I've benchmarked them and they both have the same performance, so I guess it's a matter of preference. Perhaps Howard could chime in:
auto now = system_clock::now();
//Cast the time point to ms, then get its duration, then get the duration's count.
auto ms = time_point_cast<milliseconds>(now).time_since_epoch().count();
//Get the time point's duration, then cast to ms, then get its count.
auto ms = duration_cast<milliseconds>(tpBid.time_since_epoch()).count();
The first one reads more clearly in my mind going from left to right.
time_point
objects only support arithmetic with other time_point
or duration
objects.
You'll need to convert your long
to a duration
of specified units, then your code should work correctly.
Source: Stackoverflow.com