libcxx/include/__chrono/convert_to_tm.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___CHRONO_CONVERT_TO_TM_H
  11 #define _LIBCPP___CHRONO_CONVERT_TO_TM_H
  12
  13 #include <__chrono/calendar.h>
  14 #include <__chrono/concepts.h>
  15 #include <__chrono/day.h>
  16 #include <__chrono/duration.h>
  17 #include <__chrono/file_clock.h>
  18 #include <__chrono/hh_mm_ss.h>
  19 #include <__chrono/local_info.h>
  20 #include <__chrono/month.h>
  21 #include <__chrono/month_weekday.h>
  22 #include <__chrono/monthday.h>
  23 #include <__chrono/statically_widen.h>
  24 #include <__chrono/sys_info.h>
  25 #include <__chrono/system_clock.h>
  26 #include <__chrono/time_point.h>
  27 #include <__chrono/weekday.h>
  28 #include <__chrono/year.h>
  29 #include <__chrono/year_month.h>
  30 #include <__chrono/year_month_day.h>
  31 #include <__chrono/year_month_weekday.h>
  32 #include <__chrono/zoned_time.h>
  33 #include <__concepts/same_as.h>
  34 #include <__config>
  35 #include <__format/format_error.h>
  36 #include <__memory/addressof.h>
  37 #include <__type_traits/is_convertible.h>
  38 #include <__type_traits/is_specialization.h>
  39 #include <cstdint>
  40 #include <ctime>
  41 #include <limits>
  42
  43 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  44 #  pragma GCC system_header
  45 #endif
  46
  47 _LIBCPP_PUSH_MACROS
  48 #include <__undef_macros>
  49
  50 _LIBCPP_BEGIN_NAMESPACE_STD
  51
  52 #if _LIBCPP_STD_VER >= 20
  53
  54 // Conerts a chrono date and weekday to a given _Tm type.
  55 //
  56 // This is an implementation detail for the function
  57 //   template <class _Tm, class _ChronoT>
  58 //   _Tm __convert_to_tm(const _ChronoT& __value)
  59 //
  60 // This manually converts the two values to the proper type. It is possible to
  61 // convert from sys_days to time_t and then to _Tm. But this leads to the Y2K
  62 // bug when time_t is a 32-bit signed integer. Chrono considers years beyond
  63 // the year 2038 valid, so instead do the transformation manually.
  64 template <class _Tm, class _Date>
  65   requires(same_as<_Date, chrono::year_month_day> || same_as<_Date, chrono::year_month_day_last>)
  66 _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _Date& __date, chrono::weekday __weekday) {
  67   _Tm __result = {};
  68 #  ifdef __GLIBC__
  69   __result.tm_zone = "UTC";
  70 #  endif
  71   __result.tm_year = static_cast<int>(__date.year()) - 1900;
  72   __result.tm_mon  = static_cast<unsigned>(__date.month()) - 1;
  73   __result.tm_mday = static_cast<unsigned>(__date.day());
  74   __result.tm_wday = static_cast<unsigned>(__weekday.c_encoding());
  75   __result.tm_yday =
  76       (static_cast<chrono::sys_days>(__date) -
  77        static_cast<chrono::sys_days>(chrono::year_month_day{__date.year(), chrono::January, chrono::day{1}}))
  78           .count();
  79
  80   return __result;
  81 }
  82
  83 template <class _Tm, class _Duration>
  84 _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const chrono::sys_time<_Duration> __tp) {
  85   chrono::sys_days __days = chrono::floor<chrono::days>(__tp);
  86   chrono::year_month_day __ymd{__days};
  87
  88   _Tm __result = std::__convert_to_tm<_Tm>(chrono::year_month_day{__ymd}, chrono::weekday{__days});
  89
  90   uint64_t __sec =
  91       chrono::duration_cast<chrono::seconds>(__tp - chrono::time_point_cast<chrono::seconds>(__days)).count();
  92   __sec %= 24 * 3600;
  93   __result.tm_hour = __sec / 3600;
  94   __sec %= 3600;
  95   __result.tm_min = __sec / 60;
  96   __result.tm_sec = __sec % 60;
  97
  98   return __result;
  99 }
 100
 101 // Convert a chrono (calendar) time point, or dururation to the given _Tm type,
 102 // which must have the same properties as std::tm.
 103 template <class _Tm, class _ChronoT>
 104 _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _ChronoT& __value) {
 105   _Tm __result = {};
 106 #  ifdef __GLIBC__
 107   __result.tm_zone = "UTC";
 108 #  endif
 109
 110   if constexpr (__is_time_point<_ChronoT>) {
 111     if constexpr (same_as<typename _ChronoT::clock, chrono::system_clock>)
 112       return std::__convert_to_tm<_Tm>(__value);
 113     else if constexpr (same_as<typename _ChronoT::clock, chrono::file_clock>)
 114       return std::__convert_to_tm<_Tm>(_ChronoT::clock::to_sys(__value));
 115     else if constexpr (same_as<typename _ChronoT::clock, chrono::local_t>)
 116       return std::__convert_to_tm<_Tm>(chrono::sys_time<typename _ChronoT::duration>{__value.time_since_epoch()});
 117     else
 118       static_assert(sizeof(_ChronoT) == 0, "TODO: Add the missing clock specialization");
 119   } else if constexpr (chrono::__is_duration_v<_ChronoT>) {
 120     // [time.format]/6
 121     //   ...  However, if a flag refers to a "time of day" (e.g. %H, %I, %p,
 122     //   etc.), then a specialization of duration is interpreted as the time of
 123     //   day elapsed since midnight.
 124
 125     // Not all values can be converted to hours, it may run into ratio
 126     // conversion errors. In that case the conversion to seconds works.
 127     if constexpr (is_convertible_v<_ChronoT, chrono::hours>) {
 128       auto __hour      = chrono::floor<chrono::hours>(__value);
 129       auto __sec       = chrono::duration_cast<chrono::seconds>(__value - __hour);
 130       __result.tm_hour = __hour.count() % 24;
 131       __result.tm_min  = __sec.count() / 60;
 132       __result.tm_sec  = __sec.count() % 60;
 133     } else {
 134       uint64_t __sec = chrono::duration_cast<chrono::seconds>(__value).count();
 135       __sec %= 24 * 3600;
 136       __result.tm_hour = __sec / 3600;
 137       __sec %= 3600;
 138       __result.tm_min = __sec / 60;
 139       __result.tm_sec = __sec % 60;
 140     }
 141   } else if constexpr (same_as<_ChronoT, chrono::day>)
 142     __result.tm_mday = static_cast<unsigned>(__value);
 143   else if constexpr (same_as<_ChronoT, chrono::month>)
 144     __result.tm_mon = static_cast<unsigned>(__value) - 1;
 145   else if constexpr (same_as<_ChronoT, chrono::year>)
 146     __result.tm_year = static_cast<int>(__value) - 1900;
 147   else if constexpr (same_as<_ChronoT, chrono::weekday>)
 148     __result.tm_wday = __value.c_encoding();
 149   else if constexpr (same_as<_ChronoT, chrono::weekday_indexed> || same_as<_ChronoT, chrono::weekday_last>)
 150     __result.tm_wday = __value.weekday().c_encoding();
 151   else if constexpr (same_as<_ChronoT, chrono::month_day>) {
 152     __result.tm_mday = static_cast<unsigned>(__value.day());
 153     __result.tm_mon  = static_cast<unsigned>(__value.month()) - 1;
 154   } else if constexpr (same_as<_ChronoT, chrono::month_day_last>) {
 155     __result.tm_mon = static_cast<unsigned>(__value.month()) - 1;
 156   } else if constexpr (same_as<_ChronoT, chrono::month_weekday> || same_as<_ChronoT, chrono::month_weekday_last>) {
 157     __result.tm_wday = __value.weekday_indexed().weekday().c_encoding();
 158     __result.tm_mon  = static_cast<unsigned>(__value.month()) - 1;
 159   } else if constexpr (same_as<_ChronoT, chrono::year_month>) {
 160     __result.tm_year = static_cast<int>(__value.year()) - 1900;
 161     __result.tm_mon  = static_cast<unsigned>(__value.month()) - 1;
 162   } else if constexpr (same_as<_ChronoT, chrono::year_month_day> || same_as<_ChronoT, chrono::year_month_day_last>) {
 163     return std::__convert_to_tm<_Tm>(
 164         chrono::year_month_day{__value}, chrono::weekday{static_cast<chrono::sys_days>(__value)});
 165   } else if constexpr (same_as<_ChronoT, chrono::year_month_weekday> ||
 166                        same_as<_ChronoT, chrono::year_month_weekday_last>) {
 167     return std::__convert_to_tm<_Tm>(chrono::year_month_day{static_cast<chrono::sys_days>(__value)}, __value.weekday());
 168   } else if constexpr (__is_hh_mm_ss<_ChronoT>) {
 169     __result.tm_sec = __value.seconds().count();
 170     __result.tm_min = __value.minutes().count();
 171     // In libc++ hours is stored as a long. The type in std::tm is an int. So
 172     // the overflow can only occur when hour uses more bits than an int
 173     // provides.
 174     if constexpr (sizeof(std::chrono::hours::rep) > sizeof(__result.tm_hour))
 175       if (__value.hours().count() > std::numeric_limits<decltype(__result.tm_hour)>::max())
 176         std::__throw_format_error("Formatting hh_mm_ss, encountered an hour overflow");
 177     __result.tm_hour = __value.hours().count();
 178 #  if !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
 179   } else if constexpr (same_as<_ChronoT, chrono::sys_info>) {
 180     // Has no time information.
 181   } else if constexpr (same_as<_ChronoT, chrono::local_info>) {
 182     // Has no time information.
 183 #    if _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM && _LIBCPP_HAS_LOCALIZATION
 184   } else if constexpr (__is_specialization_v<_ChronoT, chrono::zoned_time>) {
 185     return std::__convert_to_tm<_Tm>(
 186         chrono::sys_time<typename _ChronoT::duration>{__value.get_local_time().time_since_epoch()});
 187 #    endif
 188 #  endif // !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
 189   } else
 190     static_assert(sizeof(_ChronoT) == 0, "Add the missing type specialization");
 191
 192   return __result;
 193 }
 194
 195 #endif // if _LIBCPP_STD_VER >= 20
 196
 197 _LIBCPP_END_NAMESPACE_STD
 198
 199 _LIBCPP_POP_MACROS
 200
 201 #endif // _LIBCPP___CHRONO_CONVERT_TO_TM_H