Boost date add one day, non standard GMT string

Question

In C++ what is the simplest way to add one day to a date in this format:

"20090629-05:57:43"

Probably using Boost 1.36 - Boost::date, Boost::posix_date or any other boost or std library functionality, I'm not interested in other libraries.

So far I came up with:

• format the string (split date and time parts as string op) to be able to initialize boost::gregorian::date, date expects format like:

  "2009-06-29 05:57:43"

  I have

  "20090629-05:57:43"

• add one day (boost date_duration stuff)

• convert back to_simple_string and append the time part (string operation)

Is there any easier/niftier way to do this?

I am looking at run time efficiency.

Example code for the above steps:

using namespace boost::gregorian;
string orig("20090629-05:57:43");
string dday(orig.substr(0,8));
string dtime(orig.substr(8));

date d(from_undelimited_string(dday));
date_duration dd(1);
d += dd;
string result(to_iso_string(d) + dtime);

result:

20090630-05:57:43

Answer 1

That's pretty close to the simplest method I know of. About the only way to simplify it further would be using facets for the I/O stuff, to eliminate the need for string manipulation:

#include <iostream>
#include <sstream>
#include <locale>
#include <boost/date_time.hpp>

using namespace boost::local_time;

int main() {
 std::stringstream ss;
 local_time_facet* output_facet = new local_time_facet();
 local_time_input_facet* input_facet = new local_time_input_facet();
 ss.imbue(std::locale(std::locale::classic(), output_facet));
 ss.imbue(std::locale(ss.getloc(), input_facet));

 local_date_time ldt(not_a_date_time);

 input_facet->format("%Y%m%d-%H:%M:%S");
 ss.str("20090629-05:57:43");
 ss >> ldt;

 output_facet->format("%Y%m%d-%H:%M:%S");
 ss.str(std::string());
 ss << ldt;

 std::cout << ss.str() << std::endl;
}

That's longer, and arguably harder to understand, though. I haven't tried to prove it, but I suspect it would be about equal runtime-efficiency that way.