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_SRC_INCLUDE_TZDB_TYPES_PRIVATE_H
13#define __LIBCPP_SRC_INCLUDE_TZDB_TYPES_PRIVATE_H
14
15#include <chrono>
16#include <string>
17#include <utility>
18#include <variant>
19#include <vector>
20
21_LIBCPP_BEGIN_NAMESPACE_STD
22
23// TODO TZDB
24// The helper classes in this header have no constructor but are loaded with
25// dedicated parse functions. In the original design this header was public and
26// the parsing was done in the dylib. In that design having constructors would
27// expand the ABI interface. Since this header is now in the dylib that design
28// should be reconsidered. (For now the design is kept as is, in case this
29// header needs to be public for unforseen reasons.)
30
31namespace chrono::__tz {
32
33// Sun>=8 first Sunday on or after the eighth
34// Sun<=25 last Sunday on or before the 25th
35struct __constrained_weekday {
36 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI year_month_day operator()(year __year, month __month) const {
37 auto __result = static_cast<sys_days>(year_month_day{__year, __month, __day});
38 weekday __wd{static_cast<sys_days>(__result)};
39
40 if (__comparison == __le)
41 __result -= __wd - __weekday;
42 else
43 __result += __weekday - __wd;
44
45 return __result;
46 }
47
48 weekday __weekday;
49 enum __comparison_t { __le, __ge } __comparison;
50 day __day;
51};
52
53// The on field has a few alternative presentations
54// 5 the fifth of the month
55// lastSun the last Sunday in the month
56// lastMon the last Monday in the month
57// Sun>=8 first Sunday on or after the eighth
58// Sun<=25 last Sunday on or before the 25th
59using __on = variant<day, weekday_last, __constrained_weekday>;
60
61enum class __clock { __local, __standard, __universal };
62
63struct __at {
64 seconds __time{0};
65 __tz::__clock __clock{__tz::__clock::__local};
66};
67
68struct __save {
69 seconds __time;
70 bool __is_dst;
71};
72
73// The names of the fields match the fields of a Rule.
74struct __rule {
75 year __from;
76 year __to;
77 month __in;
78 __tz::__on __on;
79 __tz::__at __at;
80 __tz::__save __save;
81 string __letters;
82};
83
84using __rules_storage_type = std::vector<std::pair<string, vector<__tz::__rule>>>; // TODO TZDB use flat_map;
85
86struct __continuation {
87 // Non-owning link to the RULE entries.
88 __tz::__rules_storage_type* __rule_database_;
89
90 seconds __stdoff;
91
92 // The RULES is either a SAVE or a NAME.
93 // The size_t is used as cache. After loading the rules they are
94 // sorted and remain stable, then an index in the vector can be
95 // used.
96 // If this field contains - then standard time always
97 // applies. This is indicated by the monostate.
98 // TODO TZDB Investigate implantation the size_t based caching.
99 using __rules_t = variant<monostate, __tz::__save, string /*, size_t*/>;
100
101 __rules_t __rules;
102
103 string __format;
104 // TODO TZDB the until field can contain more than just a year.
105 // Parts of the UNTIL, the optional parts are default initialized
106 // optional<year> __until_;
107 year __year = chrono::year::min();
108 month __in{January};
109 __tz::__on __on{chrono::day{1}};
110 __tz::__at __at{chrono::seconds{0}, __tz::__clock::__local};
111};
112
113} // namespace chrono::__tz
114
115_LIBCPP_END_NAMESPACE_STD
116
117#endif // __LIBCPP_SRC_INCLUDE_TZDB_TYPES_PRIVATE_H
118

source code of libcxx/src/experimental/include/tzdb/types_private.h