seconds_since_epoch.cpp

C++的一个好库。。。现在很流行

/* This example demonstrates the use of the time zone database and 
 * local time to calculate the number of seconds since the UTC
 * time_t epoch 1970-01-01 00:00:00.  Note that the selected timezone
 * could be any timezone supported in the time zone database file which
 * can be modified and updated as needed by the user.
 *
 * To solve this problem the following steps are required:
 * 1) Get a timezone from the tz database for the local time
 * 2) Construct a local time using the timezone
 * 3) Construct a posix_time::ptime for the time_t epoch time
 * 4) Convert the local_time to utc and subtract the epoch time
 * 
 */

#include "boost/date_time/local_time/local_time.hpp"
#include <iostream>

int main()
{
  using namespace boost::gregorian; 
  using namespace boost::local_time;
  using namespace boost::posix_time;
  
  tz_database tz_db;
  try {
    tz_db.load_from_file("../data/date_time_zonespec.csv");
  }catch(data_not_accessible dna) {
    std::cerr << "Error with time zone data file: " << dna.what() << std::endl;
    exit(EXIT_FAILURE);
  }catch(bad_field_count bfc) {
    std::cerr << "Error with time zone data file: " << bfc.what() << std::endl;
    exit(EXIT_FAILURE);
  }

  time_zone_ptr nyc_tz = tz_db.time_zone_from_region("America/New_York");
  date in_date(2004,10,04);
  time_duration td(12,14,32);
  // construct with local time value
  // create not-a-date-time if invalid (eg: in dst transition)
  local_date_time nyc_time(in_date, 
                           td, 
                           nyc_tz, 
                           local_date_time::NOT_DATE_TIME_ON_ERROR);

  std::cout << nyc_time << std::endl;

  ptime time_t_epoch(date(1970,1,1)); 
  std::cout << time_t_epoch << std::endl;

  // first convert nyc_time to utc via the utc_time() 
  // call and subtract the ptime.
  time_duration diff = nyc_time.utc_time() - time_t_epoch;

  //Expected 1096906472
  std::cout << "Seconds diff: " << diff.total_seconds() << std::endl;

}


/*  Copyright 2005: CrystalClear Software, Inc
 *  http://www.crystalclearsoftware.com
 *
 *  Subject to the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
 */