date_time/xmldoc/ex_meeting_planner.xml

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<!-- Copyright (c) 2001-2005 CrystalClear Software, Inc.
     Subject to the Boost Software License, Version 1.0. 
     (See accompanying file LICENSE_1_0.txt or  http://www.boost.org/LICENSE_1_0.txt)
-->

<section id="date_time.examples.meeting_planner">
  <title>Teleconference Scheduler (partial listing)</title>

  <para> 
    The Teleconference Scheduler is a Qt based example (found in the examples/qt directory). Partial listings of <link linkend="meeting_planner_hpp">meeting_planner.hpp</link> and <link linkend="planner_form_cpp">planner_form.cpp</link> are provided to illustrate techniques for using the local_date_time and tz_database objects. 
  </para>
  
  <anchor id="planner_form_cpp" />
  <para>
    The planner_form class is derived from a QDialog. This listing illustrates the initialization of a tz_database object and using it to populate combo boxes with region lists. Only the init function is listed here for the sake of brevity.
  </para>
  <programlisting>
    <![CDATA[

  void planner_form::init() {
    try{
      tz_db.load_from_file("../../data/date_time_zonespec.csv");
    }catch(boost::local_time::data_not_accessible dna) {
      std::cerr << "Error with time zone data file: " << dna.what() << std::endl;
      exit(EXIT_FAILURE);
    }catch(boost::local_time::bad_field_count bfc) {
      std::cerr << "Error with time zone data file: " << bfc.what() << std::endl;
      exit(EXIT_FAILURE);
    }

    // populate combo boxes with region names
    typedef std::vector<std::string> vect;
    vect regions = tz_db.region_list();
    vect::const_iterator itr = regions.begin();
    while(itr != regions.end()) {
      comboBox1->insertItem(*itr);
      comboBox2->insertItem(*itr);
      comboBox3->insertItem(*itr);
      ++itr;
    }
    comboBox1->insertItem("<Select Region>", 0);
    comboBox2->insertItem("<Select Region>", 0);
    comboBox3->insertItem("<Select Region>", 0);

    // set up dateEdit
    dateEdit2->setSeparator("-");

    this->reset();
  }

    ]]>
  </programlisting>
  
  <anchor id="meeting_planner_hpp" />
  <para>
    This class coordinates local times across multiple time zones. It accomplishes this by iterating across a collection of time zones and verifying that the target time falls within a set period (a workday).
  </para>
  <programlisting>
    <![CDATA[

  /* The heart of the meeting_planner is the synchronization of different
   * time zones to a single point in time.
   * The class takes a vector of regions and a date. The default time
   * range is 9am to 5pm but can be changed.
   * The resulting time specs are returned as a vector of strings
   */


  #include "boost/date_time/gregorian/gregorian.hpp"
  #include "boost/date_time/posix_time/posix_time.hpp"
  #include "boost/date_time/local_time/local_time.hpp"
  #include "boost/shared_ptr.hpp"
  #include <string>
  #include <vector>
  #include <locale>

  using namespace boost;
  using namespace local_time;
  using namespace posix_time;

  //! Coordinates meeting times accounting for time zone differences
  class meeting_planner {
    public:
      typedef std::vector<shared_ptr<time_zone_base> > vector_type;
      // a multimap is used so time_zones can be sorted according to utc_offset
      typedef std::multimap<posix_time::time_duration, shared_ptr<time_zone_base> > zone_map_type;
      typedef std::vector<std::string> result_type;
      
      meeting_planner(const gregorian::date& d, const vector_type& v)
        : l_time(posix_time::not_a_date_time, shared_ptr<time_zone_base>()),
          workday(ptime(d,hours(9)), time_duration(8,0,0,1))
      {
        vector_type::const_iterator iter = v.begin();
        while(iter != v.end()) {
          time_duration offset(0,0,0);
          if(*iter == NULL) {
            offset = hours(0);
          }
          else{
            // null pointers may wind up in the vector
            // TODO: this should be fixed in tz_database
            offset = (*iter)->base_utc_offset();
          }
          zones.insert(zone_map_type::value_type(offset, *iter));
          ++iter;
        }

        // set l_time to noon UTC
        l_time = local_date_time(posix_time::ptime(d, posix_time::hours(12)),
                                 shared_ptr<time_zone_base>());
      }

      //! Changes range of valid meeting times (ie. The hours in a workday) times are inclusive
      void change_range(const time_duration& start, const time_duration& end)
      {
        ptime pt(l_time.date(), start);
        // add one unit to make the give times inclusive
        workday = time_period(pt, (end - start) + time_duration::unit());
      }

      //! strings returned in the form of "yyyy-Mon-dd: hh:mm Zzz [repeat]"
      result_type coordinate_time() const
      {
        using namespace posix_time;

        result_type result;
        bool flag = true;
        std::stringstream ss;
        ss.str("");
       
        // set the output format for local_date_time to only give 
        // time_of_day & zone offset
        typedef boost::date_time::time_facet<local_date_time, char> ldt_facet;
        ldt_facet* timefacet = new ldt_facet("%H:%M (%q)"); 
        std::locale loc(std::locale::classic(), timefacet);
        ss.imbue(loc);
           
        // backup a full day and start iterating from there
        // I went overkill because I've got no decent 
        // algorithm to set a starting point (yet)
        local_date_time tmp = l_time - gregorian::days(1);
        zone_map_type::const_iterator iter; 
        for(int i = 0; i < 48; ++i) {
          iter = zones.begin();
          flag = true;
          tmp += posix_time::hours(1);
          
          while(iter != zones.end() && flag) {
            if(!workday.contains(tmp.local_time_in(iter->second).local_time())) {
              flag = false;
            }
            ++iter;
          }

          if(flag) { 
            iter = zones.begin();
            ss << tmp.date() << ':';
            while(iter != zones.end()) {
              ss << ' ' << tmp.local_time_in(iter->second);
              ++iter;
              if(iter != zones.end()) {
                ss << ',';
              }
            }
            result.push_back(ss.str());
            ss.str("");
          }
        }
        if(result.empty()) {
          result.push_back("Scheduling within the time period given is not possible for these time zones.");
        }
        return result;
      }
      
    private:
      zone_map_type zones;
      local_date_time l_time;
      time_period workday;
  };

    ]]>
  </programlisting>
</section>