libcxx/include/__chrono/time_zone.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 // For information see https://libcxx.llvm.org/DesignDocs/TimeZone.html
  11
  12 #ifndef _LIBCPP___CHRONO_TIME_ZONE_H
  13 #define _LIBCPP___CHRONO_TIME_ZONE_H
  14
  15 #include <version>
  16 // Enable the contents of the header only when libc++ was built with experimental features enabled.
  17 #if !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
  18
  19 #  include <__chrono/calendar.h>
  20 #  include <__chrono/duration.h>
  21 #  include <__chrono/exception.h>
  22 #  include <__chrono/local_info.h>
  23 #  include <__chrono/sys_info.h>
  24 #  include <__chrono/system_clock.h>
  25 #  include <__compare/strong_order.h>
  26 #  include <__config>
  27 #  include <__memory/unique_ptr.h>
  28 #  include <__type_traits/common_type.h>
  29 #  include <string_view>
  30
  31 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  32 #    pragma GCC system_header
  33 #  endif
  34
  35 _LIBCPP_PUSH_MACROS
  36 #  include <__undef_macros>
  37
  38 _LIBCPP_BEGIN_NAMESPACE_STD
  39
  40 #  if _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM && _LIBCPP_HAS_LOCALIZATION
  41
  42 namespace chrono {
  43
  44 enum class choose { earliest, latest };
  45
  46 class _LIBCPP_AVAILABILITY_TZDB time_zone {
  47   _LIBCPP_HIDE_FROM_ABI time_zone() = default;
  48
  49 public:
  50   class __impl; // public so it can be used by make_unique.
  51
  52   // The "constructor".
  53   //
  54   // The default constructor is private to avoid the constructor from being
  55   // part of the ABI. Instead use an __ugly_named function as an ABI interface,
  56   // since that gives us the ability to change it in the future.
  57   [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI static time_zone __create(unique_ptr<__impl>&& __p);
  58
  59   _LIBCPP_EXPORTED_FROM_ABI ~time_zone();
  60
  61   _LIBCPP_HIDE_FROM_ABI time_zone(time_zone&&)            = default;
  62   _LIBCPP_HIDE_FROM_ABI time_zone& operator=(time_zone&&) = default;
  63
  64   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI string_view name() const noexcept { return __name(); }
  65
  66   template <class _Duration>
  67   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI sys_info get_info(const sys_time<_Duration>& __time) const {
  68     return __get_info(chrono::time_point_cast<seconds>(__time));
  69   }
  70
  71   template <class _Duration>
  72   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI local_info get_info(const local_time<_Duration>& __time) const {
  73     return __get_info(chrono::time_point_cast<seconds>(__time));
  74   }
  75
  76   // We don't apply nodiscard here since this function throws on many inputs,
  77   // so it could be used as a validation.
  78   template <class _Duration>
  79   _LIBCPP_HIDE_FROM_ABI sys_time<common_type_t<_Duration, seconds>> to_sys(const local_time<_Duration>& __time) const {
  80     local_info __info = get_info(__time);
  81     switch (__info.result) {
  82     case local_info::unique:
  83       return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
  84
  85     case local_info::nonexistent:
  86       chrono::__throw_nonexistent_local_time(__time, __info);
  87
  88     case local_info::ambiguous:
  89       chrono::__throw_ambiguous_local_time(__time, __info);
  90     }
  91
  92     // TODO TZDB The Standard does not specify anything in these cases.
  93     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
  94         __info.result != -1, "cannot convert the local time; it would be before the minimum system clock value");
  95     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
  96         __info.result != -2, "cannot convert the local time; it would be after the maximum system clock value");
  97
  98     return {};
  99   }
 100
 101   template <class _Duration>
 102   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI sys_time<common_type_t<_Duration, seconds>>
 103   to_sys(const local_time<_Duration>& __time, choose __z) const {
 104     local_info __info = get_info(__time);
 105     switch (__info.result) {
 106     case local_info::unique:
 107     case local_info::nonexistent: // first and second are the same
 108       return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
 109
 110     case local_info::ambiguous:
 111       switch (__z) {
 112       case choose::earliest:
 113         return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
 114
 115       case choose::latest:
 116         return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.second.offset};
 117
 118         // Note a value out of bounds is not specified.
 119       }
 120     }
 121
 122     // TODO TZDB The standard does not specify anything in these cases.
 123     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
 124         __info.result != -1, "cannot convert the local time; it would be before the minimum system clock value");
 125     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
 126         __info.result != -2, "cannot convert the local time; it would be after the maximum system clock value");
 127
 128     return {};
 129   }
 130
 131   template <class _Duration>
 132   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI local_time<common_type_t<_Duration, seconds>>
 133   to_local(const sys_time<_Duration>& __time) const {
 134     using _Dp = common_type_t<_Duration, seconds>;
 135
 136     sys_info __info = get_info(__time);
 137
 138     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
 139         __info.offset >= chrono::seconds{0} || __time.time_since_epoch() >= _Dp::min() - __info.offset,
 140         "cannot convert the system time; it would be before the minimum local clock value");
 141
 142     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
 143         __info.offset <= chrono::seconds{0} || __time.time_since_epoch() <= _Dp::max() - __info.offset,
 144         "cannot convert the system time; it would be after the maximum local clock value");
 145
 146     return local_time<_Dp>{__time.time_since_epoch() + __info.offset};
 147   }
 148
 149   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI const __impl& __implementation() const noexcept { return *__impl_; }
 150
 151 private:
 152   [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI string_view __name() const noexcept;
 153
 154   [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI sys_info __get_info(sys_seconds __time) const;
 155   [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI local_info __get_info(local_seconds __time) const;
 156
 157   unique_ptr<__impl> __impl_;
 158 };
 159
 160 [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline bool
 161 operator==(const time_zone& __x, const time_zone& __y) noexcept {
 162   return __x.name() == __y.name();
 163 }
 164
 165 [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline strong_ordering
 166 operator<=>(const time_zone& __x, const time_zone& __y) noexcept {
 167   return __x.name() <=> __y.name();
 168 }
 169
 170 } // namespace chrono
 171
 172 #  endif // _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM &&
 173          // _LIBCPP_HAS_LOCALIZATION
 174
 175 _LIBCPP_END_NAMESPACE_STD
 176
 177 _LIBCPP_POP_MACROS
 178
 179 #endif // !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
 180
 181 #endif // _LIBCPP___CHRONO_TIME_ZONE_H