[libcxx-commits] [libcxx] [libc++][chrono] implements TAI clock. (PR #125550)
Louis Dionne via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Feb 4 09:09:03 PST 2025
================
@@ -0,0 +1,159 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++20
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// <chrono>
+//
+// class tai_clock;
+
+// static tai_time<common_type_t<_Duration, seconds>>
+// from_utc(const utc<_Duration>& __time) noexcept;
+
+#include <chrono>
+#include <cassert>
+#include <source_location>
+
+#include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
+
+static void test_known_values() {
+ namespace cr = std::chrono;
+ using namespace std::literals::chrono_literals;
+ constexpr auto unix_to_tai_epoch_offset = cr::sys_days{cr::January / 1 / 1970} - cr::sys_days{cr::January / 1 / 1958};
+
+ // [time.clock.tai.overview]/1
+ // ... 1958-01-01 00:00:00 TAI is equivalent to 1957-12-31 23:59:50 UTC
+ // ... 2000-01-01 00:00:00 UTC is equivalent to 2000-01-01 00:00:32 TAI
+
+ assert(cr::tai_clock::from_utc(cr::utc_clock::from_sys(cr::sys_days{cr::January / 1 / 1958} - 10s)) ==
+ cr::tai_seconds{0s});
+
+ assert(cr::tai_clock::from_utc(cr::utc_clock::from_sys(cr::sys_days{cr::January / 1 / 2000})) ==
+ cr::tai_seconds{(cr::sys_days{cr::January / 1 / 2000} + unix_to_tai_epoch_offset).time_since_epoch()} + 32s);
+}
+
+template <class Duration>
+static void test_leap_seconds(std::chrono::utc_time<Duration> utc,
+ std::chrono::tai_time<Duration> expected,
+ std::source_location loc = std::source_location::current()) {
+ auto tai = std::chrono::tai_clock::from_utc(utc);
+ TEST_REQUIRE(tai == expected,
+ TEST_WRITE_CONCATENATED(loc, "\nExpected output ", expected, "\nActual output ", tai, '\n'));
+}
+
+// Tests set if existing database entries at the time of writing.
+static void test_transitions() {
+ using namespace std::literals::chrono_literals;
+ namespace cr = std::chrono;
+
+ // "sys" is the time of the transition to the next leap second.
+ // "elapsed" is the number of leap seconds before the transition.
+ auto test_transition = [](cr::sys_days sys, cr::seconds elapsed) {
+ constexpr auto unix_to_tai_epoch_offset =
+ cr::sys_days{cr::January / 1 / 1970} - cr::sys_days{cr::January / 1 / 1958};
+ cr::tai_seconds tai{sys.time_since_epoch() + unix_to_tai_epoch_offset + elapsed};
+
+ test_leap_seconds(cr::utc_clock::from_sys(sys - 1ns), tai - 1ns);
+ test_leap_seconds(cr::utc_clock::from_sys(sys), tai + 1s);
+ test_leap_seconds(cr::utc_clock::from_sys(sys) + 1ns, tai + 1s + 1ns);
+ };
+
+ // Transitions from the start of UTC.
+ test_transition(cr::sys_days{cr::July / 1 / 1972}, 10s);
+ test_transition(cr::sys_days{cr::January / 1 / 1973}, 11s);
+ test_transition(cr::sys_days{cr::January / 1 / 1974}, 12s);
+ test_transition(cr::sys_days{cr::January / 1 / 1975}, 13s);
+ test_transition(cr::sys_days{cr::January / 1 / 1976}, 14s);
+ test_transition(cr::sys_days{cr::January / 1 / 1977}, 15s);
+ test_transition(cr::sys_days{cr::January / 1 / 1978}, 16s);
+ test_transition(cr::sys_days{cr::January / 1 / 1979}, 17s);
+ test_transition(cr::sys_days{cr::January / 1 / 1980}, 18s);
+ test_transition(cr::sys_days{cr::July / 1 / 1981}, 19s);
+ test_transition(cr::sys_days{cr::July / 1 / 1982}, 20s);
+ test_transition(cr::sys_days{cr::July / 1 / 1983}, 21s);
+ test_transition(cr::sys_days{cr::July / 1 / 1985}, 22s);
+ test_transition(cr::sys_days{cr::January / 1 / 1988}, 23s);
+ test_transition(cr::sys_days{cr::January / 1 / 1990}, 24s);
+ test_transition(cr::sys_days{cr::January / 1 / 1991}, 25s);
+ test_transition(cr::sys_days{cr::July / 1 / 1992}, 26s);
+ test_transition(cr::sys_days{cr::July / 1 / 1993}, 27s);
+ test_transition(cr::sys_days{cr::July / 1 / 1994}, 28s);
+ test_transition(cr::sys_days{cr::January / 1 / 1996}, 29s);
+ test_transition(cr::sys_days{cr::July / 1 / 1997}, 30s);
+ test_transition(cr::sys_days{cr::January / 1 / 1999}, 31s);
+ test_transition(cr::sys_days{cr::January / 1 / 2006}, 32s);
+ test_transition(cr::sys_days{cr::January / 1 / 2009}, 33s);
+ test_transition(cr::sys_days{cr::July / 1 / 2012}, 34s);
+ test_transition(cr::sys_days{cr::July / 1 / 2015}, 35s);
+ test_transition(cr::sys_days{cr::January / 1 / 2017}, 36s);
+}
+
+// Tests whether the return type is the expected type.
+static void test_return_type() {
+ using namespace std::literals::chrono_literals;
+ namespace cr = std::chrono;
+
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::nanoseconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::nanoseconds>{0ns});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::microseconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::microseconds>{0us});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::milliseconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::milliseconds>{0ms});
+ }
+
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::seconds>{cr::seconds{0}});
+ }
+
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::minutes>{cr::minutes{0}});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::hours>{cr::hours{0}});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::days>{cr::days{0}});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::weeks>{cr::weeks{0}});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::months>{cr::months{0}});
+ }
+ {
+ [[maybe_unused]] std::same_as<cr::tai_time<cr::seconds>> decltype(auto) _ =
+ cr::tai_clock::from_utc(cr::utc_time<cr::years>{cr::years{0}});
+ }
+}
+
+int main(int, const char**) {
+ using namespace std::literals::chrono_literals;
+ std::chrono::utc_seconds time = std::chrono::utc_seconds{0s};
+ static_assert(noexcept(std::chrono::tai_clock::from_utc(time)));
+
+ test_known_values();
+ test_transitions();
+ test_return_type();
----------------
ldionne wrote:
`return 0` (also below)
https://github.com/llvm/llvm-project/pull/125550
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