How do I instantiate a boost::date_time::time_duration with nanoseconds? - boost

Question

I feel like I'm missing something obvious here. I can easily make a time_duration with milliseconds, microseconds, or seconds by doing:
time_duration t1 = seconds(1);
time_duration t2 = milliseconds(1000);
time_duration t3 = microseconds(1000000);
But there's no function for nanoseconds. What's the trick to converting a plain integer nanoseconds value to a time_duration?
I'm on amd64 architecture on Debian Linux. Boost version 1.55.

Answer 1

boost::posix_time::microseconds is actually subsecond_duration<boost::posix_time::time_duration, 1000000>. So...
#include <boost/date_time/posix_time/posix_time.hpp>
using nanoseconds = boost::date_time::subsecond_duration<boost::posix_time::time_duration, 1000000000>;
int main() {
boost::posix_time::time_duration t = nanoseconds(1000000000);
std::cout << t << "\n";
}
Prints
00:00:01
UPDATE
Indeed, in the Compile Options for the Boost DateTime library you can see that there's an option to select nanosecond resolution:
By default the posix_time system uses a single 64 bit integer
internally to provide a microsecond level resolution. As an
alternative, a combination of a 64 bit integer and a 32 bit integer
(96 bit resolution) can be used to provide nano-second level
resolutions. The default implementation may provide better performance
and more compact memory usage for many applications that do not
require nano-second resolutions.
To use the alternate resolution (96 bit nanosecond) the variable
BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG must be defined in the library
users project files (ie Makefile, Jamfile, etc). This macro is not
used by the Gregorian system and therefore has no effect when building
the library.
Indeed, you can check it using:
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#define BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG
#include <boost/date_time/posix_time/posix_time.hpp>
int main() {
using namespace boost::posix_time;
std::cout << nanoseconds(1000000000) << "\n";
}