63 lines
2.2 KiB
C++
63 lines
2.2 KiB
C++
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/*
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* Copyright 2021 Max Kellermann <max.kellermann@gmail.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <chrono>
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/**
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* Calculate a std::chrono::system_clock::time_point from a duration
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* relative to the UNIX epoch (1970-01-01T00:00Z).
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*/
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template<class Rep, class Period>
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[[gnu::const]]
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std::chrono::system_clock::time_point
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TimePointAfterUnixEpoch(const std::chrono::duration<Rep,Period> &d) noexcept
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{
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/* this is guaranteed to be 0 in C++20 */
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const auto unix_epoch = std::chrono::system_clock::from_time_t(0);
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return unix_epoch +
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std::chrono::duration_cast<std::chrono::system_clock::duration>(d);
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}
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/**
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* Calculate the duration that has passed since the UNIX epoch
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* (1970-01-01T00:00Z).
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*/
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[[gnu::const]]
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inline std::chrono::system_clock::duration
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DurationSinceUnixEpoch(const std::chrono::system_clock::time_point &tp) noexcept
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{
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/* this is guaranteed to be 0 in C++20 */
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const auto unix_epoch = std::chrono::system_clock::from_time_t(0);
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return tp - unix_epoch;
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}
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