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Implemented test for casting non-wall clocks and detecting that clocks cannot be casted.
Added test that detects if clock_cast<Dest>(Source) properly SFINAEs if clock's are not castable, this includes test for steady_clock that is not castable to any wall-clock. Secondly added steady_based_clock based on steady_clock (as name indicates), that clock_cast may be extended to clock non-related to wall-time (sys/utc) using conversion traits. Final example is pair of ambiguous clocks (amb1/amb2_clock) that can convert to each other either using sys_clock or utc_clock. Then the conversion from amb2 to amb1 is disambiguated via trait specialization.
This commit is contained in:
Tomasz Kamiński
parent
a9d2907fa1
commit
5a9b44a37a
247
test/tz_test/noncatsable_clock_casts.pass.cpp
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247
test/tz_test/noncatsable_clock_casts.pass.cpp
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// The MIT License (MIT)
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//
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// Copyright (c) 2017 Tomasz Kamiński
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#include "tz.h"
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#include <type_traits>
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#include <cassert>
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template<typename SourceClock, typename DestClock, typename = void>
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struct is_clock_castable
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: std::false_type
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{};
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template<typename SourceClock, typename DestClock>
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struct is_clock_castable<SourceClock, DestClock, decltype(date::clock_cast<DestClock>(typename SourceClock::time_point()), void())>
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: std::true_type
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{};
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//Clock based on steady clock, not related to wall time (sys_clock/utc_clock)
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struct steady_based_clock
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{
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using duration = std::chrono::steady_clock::duration;
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using rep = duration::rep;
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using period = duration::period;
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using time_point = std::chrono::time_point<steady_based_clock, duration>;
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static time_point now()
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{
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return time_point(std::chrono::steady_clock::now().time_since_epoch());
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}
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};
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//Traits that allow conversion between steady_clock and steady_based clock
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//Does not use wall-time clocks as rally (sys/utc)
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namespace date
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{
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template<>
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struct clock_time_conversion<steady_based_clock, std::chrono::steady_clock>
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{
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template<typename Duration>
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std::chrono::time_point<std::chrono::steady_clock, Duration>
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operator()(std::chrono::time_point<steady_based_clock, Duration> const& tp) const
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{
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using res = std::chrono::time_point<std::chrono::steady_clock, Duration>;
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return res(tp.time_since_epoch());
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}
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};
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template<>
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struct clock_time_conversion<std::chrono::steady_clock, steady_based_clock>
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{
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template<typename Duration>
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std::chrono::time_point<steady_based_clock, Duration>
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operator()(std::chrono::time_point<std::chrono::steady_clock, Duration> const& tp) const
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{
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using res = std::chrono::time_point<steady_based_clock, Duration>;
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return res(tp.time_since_epoch());
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}
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};
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}
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//Ambigous clocks both providing to/from_sys and to/from_utc
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//They are mock_ups just returning zero time_point
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struct amb1_clock
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{
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using duration = std::chrono::seconds;
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using rep = duration::rep;
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using period = duration::period;
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using time_point = std::chrono::time_point<amb1_clock>;
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static time_point now()
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<std::chrono::system_clock, Duration>
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to_sys(std::chrono::time_point<amb1_clock, Duration> const&)
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<amb1_clock, Duration>
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from_sys(std::chrono::time_point<std::chrono::system_clock, Duration> const&)
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<date::utc_clock, Duration>
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to_utc(std::chrono::time_point<amb1_clock, Duration> const&)
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<amb1_clock, Duration>
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from_utc(std::chrono::time_point<date::utc_clock, Duration> const&)
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{
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return {};
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}
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};
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struct amb2_clock
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{
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using duration = std::chrono::seconds;
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using rep = duration::rep;
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using period = duration::period;
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using time_point = std::chrono::time_point<amb2_clock>;
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static time_point now()
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<std::chrono::system_clock, Duration>
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to_sys(std::chrono::time_point<amb2_clock, Duration> const&)
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<amb2_clock, Duration>
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from_sys(std::chrono::time_point<std::chrono::system_clock, Duration> const&)
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<date::utc_clock, Duration>
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to_utc(std::chrono::time_point<amb2_clock, Duration> const&)
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{
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return {};
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}
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template<typename Duration>
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static
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std::chrono::time_point<amb2_clock, Duration>
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from_utc(std::chrono::time_point<date::utc_clock, Duration> const&)
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{
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return {};
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}
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};
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namespace date
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{
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//Disambiguates that sys_clock is preffered
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template<>
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struct clock_time_conversion<amb2_clock, amb1_clock>
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{
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template<typename Duration>
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std::chrono::time_point<amb1_clock, Duration>
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operator()(std::chrono::time_point<amb2_clock, Duration> const& tp) const
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{
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return amb1_clock::from_sys(amb2_clock::to_sys(tp));
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}
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};
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}
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int
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main()
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{
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using namespace date;
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using namespace std::chrono;
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using sys_clock = std::chrono::system_clock;
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//steady_clock (must be different that sys_clock)
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static_assert(is_clock_castable<steady_clock, steady_clock>::value, "steady_clock -> steady_clock");
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static_assert(!is_clock_castable<steady_clock, sys_clock>::value, "steady_clock -> sys_clock");
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static_assert(!is_clock_castable<sys_clock, steady_clock>::value, "sys_clock -> steady_clock");
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static_assert(!is_clock_castable<steady_clock, utc_clock>::value, "steady_clock -> utc_clock");
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static_assert(!is_clock_castable<utc_clock, steady_clock>::value, "utc_clock -> steady_clock");
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static_assert(!is_clock_castable<steady_clock, tai_clock>::value, "steady_clock -> tai_clock");
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static_assert(!is_clock_castable<tai_clock, steady_clock>::value, "tai_clock -> steady_clock");
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//steady_based_clock (unrelated to sys_clock and utc_clocks)
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static_assert(is_clock_castable<steady_based_clock, steady_based_clock>::value, "steady_based_clock -> steady_based_clock");
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static_assert(!is_clock_castable<steady_based_clock, sys_clock>::value, "steady_based_clock -> sys_clock");
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static_assert(!is_clock_castable<sys_clock, steady_based_clock>::value, "sys_clock -> steady_based_clock");
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static_assert(!is_clock_castable<steady_based_clock, utc_clock>::value, "steady_based_clock -> utc_clock");
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static_assert(!is_clock_castable<utc_clock, steady_based_clock>::value, "utc_clock -> steady_based_clock");
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static_assert(!is_clock_castable<steady_based_clock, tai_clock>::value, "steady_based_clock -> tai_clock");
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static_assert(!is_clock_castable<tai_clock, steady_based_clock>::value, "tai_clock -> steady_based_clock");
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//steady_based <-> steady_clock
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{
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auto s1 = steady_clock::time_point(steady_clock::duration(200));
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auto s2 = steady_based_clock::time_point(steady_based_clock::duration(200));
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assert(clock_cast<steady_based_clock>(s1) == s2);
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assert(clock_cast<steady_clock>(s2) == s1);
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}
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//ambX <-> sys/utc works as one rally can be used in each case, or one lead to quicker conversione
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static_assert(is_clock_castable<amb1_clock, amb1_clock>::value, "amb1_clock -> amb1_clock");
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static_assert(is_clock_castable<amb1_clock, sys_clock>::value, "amb1_clock -> sys_clock");
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static_assert(is_clock_castable<sys_clock, amb1_clock>::value, "sys_clock -> amb1_clock");
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static_assert(is_clock_castable<amb1_clock, utc_clock>::value, "amb1_clock -> utc_clock");
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static_assert(is_clock_castable<utc_clock, amb1_clock>::value, "utc_clock -> amb1_clock");
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static_assert(is_clock_castable<amb1_clock, tai_clock>::value, "amb1_clock -> tai_clock");
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static_assert(is_clock_castable<tai_clock, amb1_clock>::value, "tai_clock -> amb1_clock");
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static_assert(is_clock_castable<amb1_clock, tai_clock>::value, "amb1_clock -> tai_clock");
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static_assert(is_clock_castable<gps_clock, amb1_clock>::value, "gps_clock -> amb1_clock");
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static_assert(is_clock_castable<amb2_clock, amb2_clock>::value, "amb2_clock -> amb2_clock");
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static_assert(is_clock_castable<amb2_clock, sys_clock>::value, "amb2_clock -> sys_clock");
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static_assert(is_clock_castable<sys_clock, amb2_clock>::value, "sys_clock -> amb2_clock");
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static_assert(is_clock_castable<amb2_clock, utc_clock>::value, "amb2_clock -> utc_clock");
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static_assert(is_clock_castable<utc_clock, amb2_clock>::value, "utc_clock -> amb2_clock");
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static_assert(is_clock_castable<amb2_clock, tai_clock>::value, "amb2_clock -> tai_clock");
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static_assert(is_clock_castable<tai_clock, amb2_clock>::value, "tai_clock -> amb2_clock");
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static_assert(is_clock_castable<amb2_clock, tai_clock>::value, "amb2_clock -> tai_clock");
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static_assert(is_clock_castable<gps_clock, amb2_clock>::value, "gps_clock -> amb2_clock");
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//amb1 -> amb2: ambigous because can either go trough sys_clock or utc_clock
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static_assert(!is_clock_castable<amb1_clock, amb2_clock>::value, "amb1_clock -> amb2_clock");
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//amb2 -> amb1: disambiguated via trait specialization
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static_assert(is_clock_castable<amb2_clock, amb1_clock>::value, "amb2_clock -> amb1_clock");
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}
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