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 35 namespace chrono { 36 37 class gps_clock; 38 39 template <class _Duration> 40 using gps_time = time_point<gps_clock, _Duration>; 41 using gps_seconds = gps_time<seconds>; 42 43 class gps_clock { 44 public: 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 now()54 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static time_point now() { return from_utc(utc_clock::now()); } 55 56 template <class _Duration> 57 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static utc_time<common_type_t<_Duration, seconds>> to_utc(const gps_time<_Duration> & __time)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>> from_utc(const utc_time<_Duration> & __time)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