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  #   ˆl–Ü4ý(”†»â‚À¹q§Å£Å„o¼/ÃÇ >n    // <stop_token> -*- C++ -*-

// Copyright (C) 2019-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file include/stop_token
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_STOP_TOKEN
#define _GLIBCXX_STOP_TOKEN

#if __cplusplus > 201703L

#include <atomic>
#include <bits/std_thread.h>

#include <semaphore>

#define __cpp_lib_jthread 201911L

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /// Tag type indicating a stop_source should have no shared-stop-state.
  struct nostopstate_t { explicit nostopstate_t() = default; };
  inline constexpr nostopstate_t nostopstate{};

  class stop_source;

  /// Allow testing whether a stop request has been made on a `stop_source`.
  class stop_token
  {
  public:
    stop_token() noexcept = default;

    stop_token(const stop_token&) noexcept = default;
    stop_token(stop_token&&) noexcept = default;

    ~stop_token() = default;

    stop_token&
    operator=(const stop_token&) noexcept = default;

    stop_token&
    operator=(stop_token&&) noexcept = default;

    [[nodiscard]]
    bool
    stop_possible() const noexcept
    {
      return static_cast<bool>(_M_state) && _M_state->_M_stop_possible();
    }

    [[nodiscard]]
    bool
    stop_requested() const noexcept
    {
      return static_cast<bool>(_M_state) && _M_state->_M_stop_requested();
    }

    void
    swap(stop_token& __rhs) noexcept
    { _M_state.swap(__rhs._M_state); }

    [[nodiscard]]
    friend bool
    operator==(const stop_token& __a, const stop_token& __b)
    { return __a._M_state == __b._M_state; }

    friend void
    swap(stop_token& __lhs, stop_token& __rhs) noexcept
    { __lhs.swap(__rhs); }

  private:
    friend class stop_source;
    template<typename _Callback>
      friend class stop_callback;

    static void
    _S_yield() noexcept
    {
#if defined __i386__ || defined __x86_64__
      __builtin_ia32_pause();
#endif
      this_thread::yield();
    }

#ifndef __cpp_lib_semaphore
    struct binary_semaphore
    {
      explicit binary_semaphore(int __d) : _M_counter(__d > 0) { }

      void release() { _M_counter.fetch_add(1, memory_order::release); }

      void acquire()
      {
	int __old = 1;
	while (!_M_counter.compare_exchange_weak(__old, 0,
						 memory_order::acquire,
						 memory_order::relaxed))
	  {
	    __old = 1;
	    _S_yield();
	  }
      }

      atomic<int> _M_counter;
    };
#endif

    struct _Stop_cb
    {
      using __cb_type = void(_Stop_cb*) noexcept;
      __cb_type* _M_callback;
      _Stop_cb* _M_prev = nullptr;
      _Stop_cb* _M_next = nullptr;
      bool* _M_destroyed = nullptr;
      binary_semaphore _M_done{0};

      [[__gnu__::__nonnull__]]
      explicit
      _Stop_cb(__cb_type* __cb)
      : _M_callback(__cb)
      { }

      void _M_run() noexcept { _M_callback(this); }
    };

    struct _Stop_state_t
    {
      using value_type = uint32_t;
      static constexpr value_type _S_stop_requested_bit = 1;
      static con