utils.cpp

#include <iostream>
#include <cstdint>


inline int64_t secToNano(double sec)
{
   constexpr int64_t e9 = 1e9;
   const int64_t seconds = sec; // Truncate decimals
   const int64_t nanoseconds = (sec - seconds) * e9;
   const int64_t time = seconds * e9 + nanoseconds;

   return time;
}

inline double nanoToSec(int64_t nano)
{
   constexpr int64_t e9 = 1e9;
   const int64_t seconds = nano / e9;
   const int64_t nanoseconds = nano - seconds * e9;
   const double time = static_cast<double>(seconds) + static_cast<double>(nanoseconds) * 1e-9;

   return time;
}

int main ()
{
   double time = 1349442752.2338988781;  
   
   std::cout << (time == nanoToSec(secToNano(time))) << std::endl;
}