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_GPS_CLOCK_H
11#define _LIBCPP___CHRONO_GPS_CLOCK_H
12
13#include <version>
14// Enable the contents of the header only when libc++ was built with experimental features enabled.
15#if _LIBCPP_HAS_EXPERIMENTAL_TZDB
16
17# include <__assert>
18# include <__chrono/duration.h>
19# include <__chrono/time_point.h>
20# include <__chrono/utc_clock.h>
21# include <__config>
22# include <__type_traits/common_type.h>
23
24# if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
25# pragma GCC system_header
26# endif
27
28_LIBCPP_PUSH_MACROS
29# include <__undef_macros>
30
31_LIBCPP_BEGIN_NAMESPACE_STD
32
33# if _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM && _LIBCPP_HAS_LOCALIZATION
34
35namespace chrono {
36
37class gps_clock;
38
39template <class _Duration>
40using gps_time = time_point<gps_clock, _Duration>;
41using gps_seconds = gps_time<seconds>;
42
43class gps_clock {
44public:
45 using rep = utc_clock::rep;
46 using period = utc_clock::period;
47 using duration = chrono::duration<rep, period>;
48 using time_point = chrono::time_point<gps_clock>;
49 static constexpr bool is_steady = false; // The utc_clock is not steady.
50
51 // The static difference between UTC and GPS time as specified in the Standard.
52 static constexpr chrono::seconds __offset{315964809};
53
54 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static time_point now() { return from_utc(time: utc_clock::now()); }
55
56 template <class _Duration>
57 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static utc_time<common_type_t<_Duration, seconds>>
58 to_utc(const gps_time<_Duration>& __time) noexcept {
59 using _Rp = common_type_t<_Duration, seconds>;
60 _Duration __time_since_epoch = __time.time_since_epoch();
61 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__time_since_epoch >= utc_time<_Rp>::min().time_since_epoch() + __offset,
62 "the GPS to UTC conversion would underflow");
63
64 return utc_time<_Rp>{__time_since_epoch + __offset};
65 }
66
67 template <class _Duration>
68 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static gps_time<common_type_t<_Duration, seconds>>
69 from_utc(const utc_time<_Duration>& __time) noexcept {
70 using _Rp = common_type_t<_Duration, seconds>;
71 _Duration __time_since_epoch = __time.time_since_epoch();
72 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__time_since_epoch <= utc_time<_Rp>::max().time_since_epoch() - __offset,
73 "the UTC to GPS conversion would overflow");
74
75 return gps_time<_Rp>{__time_since_epoch - __offset};
76 }
77};
78
79} // namespace chrono
80
81# endif // _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM &&
82 // _LIBCPP_HAS_LOCALIZATION
83
84_LIBCPP_END_NAMESPACE_STD
85
86_LIBCPP_POP_MACROS
87
88#endif // _LIBCPP_HAS_EXPERIMENTAL_TZDB
89
90#endif // _LIBCPP___CHRONO_GPS_CLOCK_H
91