the time_point
constructor takes a duration
, and you can get a duration
from member time_since_epoch
. thus the question reduces to serialize a duration
value. and duration
has a constructor that takes a number of ticks, and a member function count
that produces the number of ticks.
all this just by googling std::chrono::time_point
and looking at the cppreference documentation google landed me on.
it's often a good idea to read the documentation.
Addendum: an example.
#include <chrono>
#include <iostream>
#include <typeinfo>
using namespace std;
auto main() -> int
{
using Clock = chrono::high_resolution_clock;
using Time_point = Clock::time_point;
using Duration = Clock::duration;
Time_point const t0 = Clock::now();
//Generate POD to write to disk
Duration::rep const ns0 = t0.time_since_epoch().count();
//Read POD from disk and attempt to instantiate time_point
Duration const d(ns0);
Time_point const t1(d);
cout << "Basic number type is " << typeid( ns0 ).name() << "." << endl;
if( t0 != t1 )
{
cout << "Error time points don't match!" << endl;
}
else
{
cout << "Reconstituted time is OK." << endl;
}
}
With Visual C++ 12.0 the reported basic type is __int64
, i.e. long long
, while with g++ 4.8.2 in Windows the reported type is x
, which presumably means the same.
With both compilers the reconstituted time is identical to the original.
Addendum: As noted by Dina in the comments, as of C++14 the C++ standard doesn't specify the epoch, and so to make this work across machines or with different clocks it's necessary to add additional steps that normalize the epoch for the serialized data, e.g. and most naturally to Posix time, i.e. time since since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970.