chrono.hpp

/**
 * @defgroup ion_chrono Time utilities
 * Time utilities
 *
 * @warning Depending on the clock type the and whether VDSO is used, querying clock may involve a
 * system call. Linking statically to glibc disables VDSO, for example.
 *
 * @ingroup ion
 * @file
 * @copyright
 *   SPDX-FileCopyrightText: 2025-2025 European Southern Observatory (ESO)
 
 *   SPDX-License-Identifier: LGPL-3.0-only
 */
#ifndef ION_CHRONO_HPP
#define ION_CHRONO_HPP
#include <chrono>
#include <type_traits>
 
#include <ion/detail/macros.hpp>
 
namespace ion {
 
/**
 * Blocks execution of current thread, without yielding, until specified @a time has been reached.
 *
 * @param time Time point to wait for.
 * @tparam Clock Clock type satisfying C++11 `Clock` requirements.
 */
template <class Clock, class Duration>
void WaitUntil(std::chrono::time_point<Clock, Duration> const& time) noexcept(
    std::is_nothrow_invocable_v<decltype(&Clock::now), Clock>);
 
/**
 * Blocks execution of current thread, without yielding, for specified @a duration, using a
 * steady clock.
 *
 * @param duration time duration to wait.
 */
template <class Rep, class Period>
void WaitFor(std::chrono::duration<Rep, Period> const& duration) noexcept;
 
template <class Clock, class Duration>
void WaitUntil(std::chrono::time_point<Clock, Duration> const& time) noexcept(
    std::is_nothrow_invocable_v<decltype(&Clock::now), Clock>) {
    while (Clock::now() < time) {
        ION_PAUSE();
    }
}
 
template <class Rep, class Period>
void WaitFor(std::chrono::duration<Rep, Period> const& duration) noexcept {
    WaitUntil(std::chrono::steady_clock::now() +
              std::chrono::duration_cast<std::chrono::steady_clock::duration>(duration));
}
 
}  // namespace ion
#endif  // ION_CHRONO_HPP