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.
64template <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
83template <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>(t: __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.
103template <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<_ChronoT>::value) {
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(s: "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 !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) && \
184 !defined(_LIBCPP_HAS_NO_LOCALIZATION)
185 } else if constexpr (__is_specialization_v<_ChronoT, chrono::zoned_time>) {
186 return std::__convert_to_tm<_Tm>(
187 chrono::sys_time<typename _ChronoT::duration>{__value.get_local_time().time_since_epoch()});
188# endif
189# endif // !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
190 } else
191 static_assert(sizeof(_ChronoT) == 0, "Add the missing type specialization");
192
193 return __result;
194}
195
196#endif // if _LIBCPP_STD_VER >= 20
197
198_LIBCPP_END_NAMESPACE_STD
199
200_LIBCPP_POP_MACROS
201
202#endif // _LIBCPP___CHRONO_CONVERT_TO_TM_H
203