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