87 lines
1.8 KiB
C++
87 lines
1.8 KiB
C++
#ifndef BOOST_COMPAT_LATCH_HPP_INCLUDED
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#define BOOST_COMPAT_LATCH_HPP_INCLUDED
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// Copyright 2023 Peter Dimov.
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// Copyright 2023 Christian Mazakas.
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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#include <boost/assert.hpp>
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#include <climits>
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#include <condition_variable>
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#include <mutex>
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namespace boost
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{
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namespace compat
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{
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class latch {
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private:
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std::ptrdiff_t n_;
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mutable std::mutex m_;
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mutable std::condition_variable cv_;
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public:
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explicit latch(std::ptrdiff_t expected) : n_{expected}, m_{}, cv_{} {
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BOOST_ASSERT(n_ >= 0);
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BOOST_ASSERT(n_ <= max());
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}
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latch(latch const &) = delete;
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latch &operator=(latch const &) = delete;
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~latch() = default;
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void count_down(std::ptrdiff_t n = 1) {
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std::unique_lock<std::mutex> lk(m_);
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count_down_and_notify(lk, n);
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}
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bool try_wait() const noexcept {
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std::unique_lock<std::mutex> lk(m_);
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return is_ready();
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}
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void wait() const {
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std::unique_lock<std::mutex> lk(m_);
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wait_impl(lk);
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}
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void arrive_and_wait(std::ptrdiff_t n = 1) {
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std::unique_lock<std::mutex> lk(m_);
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bool should_wait = count_down_and_notify(lk, n);
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if (should_wait) {
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wait_impl(lk);
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}
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}
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static constexpr std::ptrdiff_t max() noexcept { return PTRDIFF_MAX; }
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private:
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bool is_ready() const { return n_ == 0; }
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bool count_down_and_notify(std::unique_lock<std::mutex> &lk,
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std::ptrdiff_t n) {
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BOOST_ASSERT(n <= n_);
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n_ -= n;
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if (n_ == 0) {
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lk.unlock();
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cv_.notify_all();
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return false;
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}
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return true;
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}
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void wait_impl(std::unique_lock<std::mutex> &lk) const {
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cv_.wait(lk, [this] { return this->is_ready(); });
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}
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};
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} // namespace compat
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} // namespace boost
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#endif // #ifndef BOOST_COMPAT_LATCH_HPP_INCLUDED
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