1 #ifndef DATE_TIME_C_LOCAL_TIME_ADJUSTOR_HPP__
2 #define DATE_TIME_C_LOCAL_TIME_ADJUSTOR_HPP__
3 
4 /* Copyright (c) 2002,2003,2005 CrystalClear Software, Inc.
5  * Use, modification and distribution is subject to the
6  * Boost Software License, Version 1.0. (See accompanying
7  * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
8  * Author: Jeff Garland, Bart Garst
9  * $Date$
10  */
11 
12 /*! @file c_local_time_adjustor.hpp
13   Time adjustment calculations based on machine
14 */
15 
16 #include <stdexcept>
17 #include <boost/throw_exception.hpp>
18 #include <boost/date_time/compiler_config.hpp>
19 #include <boost/date_time/c_time.hpp>
20 #include <boost/numeric/conversion/cast.hpp>
21 
22 namespace boost {
23 namespace date_time {
24 
25   //! Adjust to / from utc using the C API
26   /*! Warning!!! This class assumes that timezone settings of the
27    *  machine are correct.  This can be a very dangerous assumption.
28    */
29   template<class time_type>
30   class c_local_adjustor {
31   public:
32     typedef typename time_type::time_duration_type time_duration_type;
33     typedef typename time_type::date_type date_type;
34     typedef typename date_type::duration_type date_duration_type;
35     //! Convert a utc time to local time
utc_to_local(const time_type & t)36     static time_type utc_to_local(const time_type& t)
37     {
38       date_type time_t_start_day(1970,1,1);
39       time_type time_t_start_time(time_t_start_day,time_duration_type(0,0,0));
40       if (t < time_t_start_time) {
41         boost::throw_exception(std::out_of_range("Cannot convert dates prior to Jan 1, 1970"));
42         BOOST_DATE_TIME_UNREACHABLE_EXPRESSION(return time_t_start_time); // should never reach
43       }
44       date_duration_type dd = t.date() - time_t_start_day;
45       time_duration_type td = t.time_of_day();
46       uint64_t t2 = static_cast<uint64_t>(dd.days())*86400 +
47                     static_cast<uint64_t>(td.hours())*3600 +
48                     static_cast<uint64_t>(td.minutes())*60 +
49                     td.seconds();
50       // detect y2038 issue and throw instead of proceed with bad time
51       std::time_t tv = boost::numeric_cast<std::time_t>(t2);
52       std::tm tms, *tms_ptr;
53       tms_ptr = c_time::localtime(&tv, &tms);
54       date_type d(static_cast<unsigned short>(tms_ptr->tm_year + 1900),
55                   static_cast<unsigned short>(tms_ptr->tm_mon + 1),
56                   static_cast<unsigned short>(tms_ptr->tm_mday));
57       time_duration_type td2(tms_ptr->tm_hour,
58                              tms_ptr->tm_min,
59                              tms_ptr->tm_sec,
60                              t.time_of_day().fractional_seconds());
61 
62       return time_type(d,td2);
63     }
64   };
65 
66 
67 
68 } } //namespace date_time
69 
70 
71 
72 #endif
73