//
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// detail/atomic_count.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef BOOST_ASIO_DETAIL_ATOMIC_COUNT_HPP
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#define BOOST_ASIO_DETAIL_ATOMIC_COUNT_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include <boost/asio/detail/config.hpp>
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#if !defined(BOOST_ASIO_HAS_THREADS)
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// Nothing to include.
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#elif defined(BOOST_ASIO_HAS_STD_ATOMIC)
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# include <atomic>
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#else // defined(BOOST_ASIO_HAS_STD_ATOMIC)
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# include <boost/detail/atomic_count.hpp>
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#endif // defined(BOOST_ASIO_HAS_STD_ATOMIC)
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namespace boost {
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namespace asio {
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namespace detail {
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#if !defined(BOOST_ASIO_HAS_THREADS)
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typedef long atomic_count;
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inline void increment(atomic_count& a, long b) { a += b; }
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inline void ref_count_up(atomic_count& a) { ++a; }
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inline bool ref_count_down(atomic_count& a) { return --a == 0; }
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#elif defined(BOOST_ASIO_HAS_STD_ATOMIC)
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typedef std::atomic<long> atomic_count;
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inline void increment(atomic_count& a, long b) { a += b; }
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inline void ref_count_up(atomic_count& a)
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{
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a.fetch_add(1, std::memory_order_relaxed);
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}
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inline bool ref_count_down(atomic_count& a)
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{
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if (a.fetch_sub(1, std::memory_order_release) == 1)
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{
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std::atomic_thread_fence(std::memory_order_acquire);
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return true;
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}
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return false;
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}
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#else // defined(BOOST_ASIO_HAS_STD_ATOMIC)
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typedef boost::detail::atomic_count atomic_count;
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inline void increment(atomic_count& a, long b) { while (b > 0) ++a, --b; }
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inline void ref_count_up(atomic_count& a) { ++a; }
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inline bool ref_count_down(atomic_count& a) { return --a == 0; }
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#endif // defined(BOOST_ASIO_HAS_STD_ATOMIC)
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} // namespace detail
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} // namespace asio
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} // namespace boost
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#endif // BOOST_ASIO_DETAIL_ATOMIC_COUNT_HPP
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