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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 _LIBCPP_HAS_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
42namespace chrono {
43
44enum class choose { earliest, latest };
45
46class _LIBCPP_AVAILABILITY_TZDB time_zone {
47 _LIBCPP_HIDE_FROM_ABI time_zone() = default;
48
49public:
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: // first and second are the same
107 return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
108
109 case local_info::nonexistent:
110 // first and second are the same
111 // All non-existing values are converted to the same time.
112 return sys_time<common_type_t<_Duration, seconds>>{__info.first.end};
113
114 case local_info::ambiguous:
115 switch (__z) {
116 case choose::earliest:
117 return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
118
119 case choose::latest:
120 return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.second.offset};
121
122 // Note a value out of bounds is not specified.
123 }
124 }
125
126 // TODO TZDB The standard does not specify anything in these cases.
127 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
128 __info.result != -1, "cannot convert the local time; it would be before the minimum system clock value");
129 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
130 __info.result != -2, "cannot convert the local time; it would be after the maximum system clock value");
131
132 return {};
133 }
134
135 template <class _Duration>
136 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI local_time<common_type_t<_Duration, seconds>>
137 to_local(const sys_time<_Duration>& __time) const {
138 using _Dp = common_type_t<_Duration, seconds>;
139
140 sys_info __info = get_info(__time);
141
142 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
143 __info.offset >= chrono::seconds{0} || __time.time_since_epoch() >= _Dp::min() - __info.offset,
144 "cannot convert the system time; it would be before the minimum local clock value");
145
146 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
147 __info.offset <= chrono::seconds{0} || __time.time_since_epoch() <= _Dp::max() - __info.offset,
148 "cannot convert the system time; it would be after the maximum local clock value");
149
150 return local_time<_Dp>{__time.time_since_epoch() + __info.offset};
151 }
152
153 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI const __impl& __implementation() const noexcept { return *__impl_; }
154
155private:
156 [[nodiscard]] _LIBCPP_EXPORTED_FROM_ABI string_view __name() const noexcept;
157
158 [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI sys_info __get_info(sys_seconds __time) const;
159 [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI local_info __get_info(local_seconds __time) const;
160
161 unique_ptr<__impl> __impl_;
162};
163
164[[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline bool
165operator==(const time_zone& __x, const time_zone& __y) noexcept {
166 return __x.name() == __y.name();
167}
168
169[[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline strong_ordering
170operator<=>(const time_zone& __x, const time_zone& __y) noexcept {
171 return __x.name() <=> __y.name();
172}
173
174} // namespace chrono
175
176# endif // _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM &&
177 // _LIBCPP_HAS_LOCALIZATION
178
179_LIBCPP_END_NAMESPACE_STD
180
181_LIBCPP_POP_MACROS
182
183#endif // _LIBCPP_HAS_EXPERIMENTAL_TZDB
184
185#endif // _LIBCPP___CHRONO_TIME_ZONE_H