libstdc++-v3/include/std/thread

// <thread> -*- C++ -*-

// Copyright (C) 2008-2021 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/thread
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_THREAD
#define _GLIBCXX_THREAD 1

#pragma GCC system_header

#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else

#if __cplusplus > 201703L
# include <compare>	// std::strong_ordering
# include <stop_token>	// std::stop_source, std::stop_token, std::nostopstate
#endif

#include <bits/std_thread.h> // std::thread, get_id, yield
#include <bits/this_thread_sleep.h> // std::this_thread::sleep_for, sleep_until

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   * @defgroup threads Threads
   * @ingroup concurrency
   *
   * Classes for thread support.
   * @{
   */

  // std::thread is defined in <bits/std_thread.h>

#if __cpp_lib_three_way_comparison
  inline strong_ordering
  operator<=>(thread::id __x, thread::id __y) noexcept
  { return __x._M_thread <=> __y._M_thread; }
#else
  inline bool
  operator!=(thread::id __x, thread::id __y) noexcept
  { return !(__x == __y); }

  inline bool
  operator<(thread::id __x, thread::id __y) noexcept
  {
    // Pthreads doesn't define any way to do this, so we just have to
    // assume native_handle_type is LessThanComparable.
    return __x._M_thread < __y._M_thread;
  }

  inline bool
  operator<=(thread::id __x, thread::id __y) noexcept
  { return !(__y < __x); }

  inline bool
  operator>(thread::id __x, thread::id __y) noexcept
  { return __y < __x; }

  inline bool
  operator>=(thread::id __x, thread::id __y) noexcept
  { return !(__x < __y); }
#endif // __cpp_lib_three_way_comparison

  template<class _CharT, class _Traits>
    inline basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
    {
      if (__id == thread::id())
	return __out << "thread::id of a non-executing thread";
      else
	return __out << __id._M_thread;
    }

#ifdef __cpp_lib_jthread

#ifndef __STRICT_ANSI__
    template<typename _Callable, typename... _Args>
      constexpr bool __pmf_expects_stop_token = false;

    template<typename _Callable, typename _Obj, typename... _Args>
      constexpr bool __pmf_expects_stop_token<_Callable, _Obj, _Args...>
	= __and_<is_member_function_pointer<remove_reference_t<_Callable>>,
		 is_invocable<_Callable, _Obj, stop_token, _Args...>>::value;
#endif

  /// A thread that can be requested to stop and automatically joined.
  class jthread
  {
  public:
    using id = thread::id;
    using native_handle_type = thread::native_handle_type;

    jthread() noexcept
    : _M_stop_source{nostopstate}
    { }

    template<typename _Callable, typename... _Args,
	     typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
					       jthread>>>
      explicit
      jthread(_Callable&& __f, _Args&&... __args)
      : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
			    std::forward<_Args>(__args)...)}
      { }

    jthread(const jthread&) = delete;
    jthread(jthread&&) noexcept = default;

    ~jthread()
    {
      if (joinable())
        {
          request_stop();
          join();
        }
    }

    jthread&
    operator=(const jthread&) = delete;

    jthread&
    operator=(jthread&& __other) noexcept
    {
      std::jthread(std::move(__other)).swap(*this);
      return *this;
    }

    void
    swap(jthread& __other) noexcept
    {
      std::swap(_M_stop_source, __other._M_stop_source);
      std::swap(_M_thread, __other._M_thread);
    }

    [[nodiscard]] bool
    joinable() const noexcept
    {
      return _M_thread.joinable();
    }

    void
    join()
    {
      _M_thread.join();
    }

    void
    detach()
    {
      _M_thread.detach();
    }

    [[nodiscard]] id
    get_id() const noexcept
    {
      return _M_thread.get_id();
    }

    [[nodiscard]] native_handle_type
    native_handle()
    {
      return _M_thread.native_handle();
    }

    [[nodiscard]] static unsigned
    hardware_concurrency() noexcept
    {
      return thread::hardware_concurrency();
    }

    [[nodiscard]] stop_source
    get_stop_source() noexcept
    {
      return _M_stop_source;
    }

    [[nodiscard]] stop_token
    get_stop_token() const noexcept
    {
      return _M_stop_source.get_token();
    }

    bool request_stop() noexcept
    {
      return _M_stop_source.request_stop();
    }

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

  private:
    template<typename _Callable, typename... _Args>
      static thread
      _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
      {
#ifndef __STRICT_ANSI__
	if constexpr (__pmf_expects_stop_token<_Callable, _Args...>)
	  return _S_create_pmf(__ssrc, __f, std::forward<_Args>(__args)...);
	else
#endif
	if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
				    decay_t<_Args>...>)
	  return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
			std::forward<_Args>(__args)...};
	else
	  {
	    static_assert(is_invocable_v<decay_t<_Callable>,
					 decay_t<_Args>...>,
			  "std::jthread arguments must be invocable after"
			  " conversion to rvalues");
	    return thread{std::forward<_Callable>(__f),
			  std::forward<_Args>(__args)...};
	  }
      }

#ifndef __STRICT_ANSI__
    template<typename _Callable, typename _Obj, typename... _Args>
      static thread
      _S_create_pmf(stop_source& __ssrc, _Callable __f, _Obj&& __obj,
		    _Args&&... __args)
      {
	return thread{__f, std::forward<_Obj>(__obj), __ssrc.get_token(),
		      std::forward<_Args>(__args)...};
      }
#endif

    stop_source _M_stop_source;
    thread _M_thread;
  };
#endif // __cpp_lib_jthread

  /// @} group threads

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif // C++11
#endif // _GLIBCXX_THREAD