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/day.h>
14 #include <__chrono/duration.h>
15 #include <__chrono/hh_mm_ss.h>
16 #include <__chrono/month.h>
17 #include <__chrono/month_weekday.h>
18 #include <__chrono/monthday.h>
19 #include <__chrono/statically_widen.h>
20 #include <__chrono/system_clock.h>
21 #include <__chrono/time_point.h>
22 #include <__chrono/weekday.h>
23 #include <__chrono/year.h>
24 #include <__chrono/year_month.h>
25 #include <__chrono/year_month_day.h>
26 #include <__chrono/year_month_weekday.h>
27 #include <__concepts/same_as.h>
28 #include <__config>
29 #include <__memory/addressof.h>
30 #include <cstdint>
31 #include <ctime>
32
33 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
34 # pragma GCC system_header
35 #endif
36
37 _LIBCPP_BEGIN_NAMESPACE_STD
38
39 #if _LIBCPP_STD_VER > 17
40
41 // Conerts a chrono date and weekday to a given _Tm type.
42 //
43 // This is an implementation detail for the function
44 // template <class _Tm, class _ChronoT>
45 // _Tm __convert_to_tm(const _ChronoT& __value)
46 //
47 // This manually converts the two values to the proper type. It is possible to
48 // convert from sys_days to time_t and then to _Tm. But this leads to the Y2K
49 // bug when time_t is a 32-bit signed integer. Chrono considers years beyond
50 // the year 2038 valid, so instead do the transformation manually.
51 template <class _Tm, class _Date>
52 requires(same_as<_Date, chrono::year_month_day> || same_as<_Date, chrono::year_month_day_last>)
__convert_to_tm(const _Date & __date,chrono::weekday __weekday)53 _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _Date& __date, chrono::weekday __weekday) {
54 _Tm __result = {};
55 # ifdef __GLIBC__
56 __result.tm_zone = "UTC";
57 # endif
58 __result.tm_year = static_cast<int>(__date.year()) - 1900;
59 __result.tm_mon = static_cast<unsigned>(__date.month()) - 1;
60 __result.tm_mday = static_cast<unsigned>(__date.day());
61 __result.tm_wday = static_cast<unsigned>(__weekday.c_encoding());
62 __result.tm_yday =
63 (static_cast<chrono::sys_days>(__date) -
64 static_cast<chrono::sys_days>(chrono::year_month_day{__date.year(), chrono::January, chrono::day{1}}))
65 .count();
66
67 return __result;
68 }
69
70 // Convert a chrono (calendar) time point, or dururation to the given _Tm type,
71 // which must have the same properties as std::tm.
72 template <class _Tm, class _ChronoT>
__convert_to_tm(const _ChronoT & __value)73 _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _ChronoT& __value) {
74 _Tm __result = {};
75 # ifdef __GLIBC__
76 __result.tm_zone = "UTC";
77 # endif
78
79 if constexpr (chrono::__is_duration<_ChronoT>::value) {
80 // [time.format]/6
81 // ... However, if a flag refers to a "time of day" (e.g. %H, %I, %p,
82 // etc.), then a specialization of duration is interpreted as the time of
83 // day elapsed since midnight.
84 uint64_t __sec = chrono::duration_cast<chrono::seconds>(__value).count();
85 __sec %= 24 * 3600;
86 __result.tm_hour = __sec / 3600;
87 __sec %= 3600;
88 __result.tm_min = __sec / 60;
89 __result.tm_sec = __sec % 60;
90 } else if constexpr (same_as<_ChronoT, chrono::day>)
91 __result.tm_mday = static_cast<unsigned>(__value);
92 else if constexpr (same_as<_ChronoT, chrono::month>)
93 __result.tm_mon = static_cast<unsigned>(__value) - 1;
94 else if constexpr (same_as<_ChronoT, chrono::year>)
95 __result.tm_year = static_cast<int>(__value) - 1900;
96 else if constexpr (same_as<_ChronoT, chrono::weekday>)
97 __result.tm_wday = __value.c_encoding();
98 else if constexpr (same_as<_ChronoT, chrono::weekday_indexed> || same_as<_ChronoT, chrono::weekday_last>)
99 __result.tm_wday = __value.weekday().c_encoding();
100 else if constexpr (same_as<_ChronoT, chrono::month_day>) {
101 __result.tm_mday = static_cast<unsigned>(__value.day());
102 __result.tm_mon = static_cast<unsigned>(__value.month()) - 1;
103 } else if constexpr (same_as<_ChronoT, chrono::month_day_last>) {
104 __result.tm_mon = static_cast<unsigned>(__value.month()) - 1;
105 } else if constexpr (same_as<_ChronoT, chrono::month_weekday> || same_as<_ChronoT, chrono::month_weekday_last>) {
106 __result.tm_wday = __value.weekday_indexed().weekday().c_encoding();
107 __result.tm_mon = static_cast<unsigned>(__value.month()) - 1;
108 } else if constexpr (same_as<_ChronoT, chrono::year_month>) {
109 __result.tm_year = static_cast<int>(__value.year()) - 1900;
110 __result.tm_mon = static_cast<unsigned>(__value.month()) - 1;
111 } else if constexpr (same_as<_ChronoT, chrono::year_month_day> || same_as<_ChronoT, chrono::year_month_day_last>) {
112 return std::__convert_to_tm<_Tm>(
113 chrono::year_month_day{__value}, chrono::weekday{static_cast<chrono::sys_days>(__value)});
114 } else if constexpr (same_as<_ChronoT, chrono::year_month_weekday> ||
115 same_as<_ChronoT, chrono::year_month_weekday_last>) {
116 return std::__convert_to_tm<_Tm>(chrono::year_month_day{static_cast<chrono::sys_days>(__value)}, __value.weekday());
117 } else
118 static_assert(sizeof(_ChronoT) == 0, "Add the missing type specialization");
119
120 return __result;
121 }
122
123 #endif //if _LIBCPP_STD_VER > 17
124
125 _LIBCPP_END_NAMESPACE_STD
126
127 #endif // _LIBCPP___CHRONO_CONVERT_TO_TM_H
128