// <thread> -*- C++ -*-
	
	// Copyright (C) 2008-2019 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
	
	#include <chrono>
	#include <memory>
	#include <tuple>
	#include <cerrno>
	#include <bits/functexcept.h>
	#include <bits/functional_hash.h>
	#include <bits/invoke.h>
	#include <bits/gthr.h>
	
	#if defined(_GLIBCXX_HAS_GTHREADS)
	
	namespace std _GLIBCXX_VISIBILITY(default)
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	
	  /**
	   * @defgroup threads Threads
	   * @ingroup concurrency
	   *
	   * Classes for thread support.
	   * @{
	   */
	
	  /// thread
	  class thread
	  {
	  public:
	    // Abstract base class for types that wrap arbitrary functors to be
	    // invoked in the new thread of execution.
	    struct _State
	    {
	      virtual ~_State();
	      virtual void _M_run() = 0;
	    };
	    using _State_ptr = unique_ptr<_State>;
	
	    typedef __gthread_t			native_handle_type;
	
	    /// thread::id
	    class id
	    {
	      native_handle_type	_M_thread;
	
	    public:
	      id() noexcept : _M_thread() { }
	
	      explicit
	      id(native_handle_type __id) : _M_thread(__id) { }
	
	    private:
	      friend class thread;
	      friend class hash<thread::id>;
	
	      friend bool
	      operator==(thread::id __x, thread::id __y) noexcept;
	
	      friend bool
	      operator<(thread::id __x, thread::id __y) noexcept;
	
	      template<class _CharT, class _Traits>
		friend basic_ostream<_CharT, _Traits>&
		operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id);
	    };
	
	  private:
	    id				_M_id;
	
	    // _GLIBCXX_RESOLVE_LIB_DEFECTS
	    // 2097.  packaged_task constructors should be constrained
	    // 3039. Unnecessary decay in thread and packaged_task
	    template<typename _Tp>
	      using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
	
	  public:
	    thread() noexcept = default;
	
	    template<typename _Callable, typename... _Args,
		     typename = _Require<__not_same<_Callable>>>
	      explicit
	      thread(_Callable&& __f, _Args&&... __args)
	      {
		static_assert( __is_invocable<typename decay<_Callable>::type,
					      typename decay<_Args>::type...>::value,
		  "std::thread arguments must be invocable after conversion to rvalues"
		  );
	
	#ifdef GTHR_ACTIVE_PROXY
		// Create a reference to pthread_create, not just the gthr weak symbol.
		auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
	#else
		auto __depend = nullptr;
	#endif
	        _M_start_thread(_S_make_state(
		      __make_invoker(std::forward<_Callable>(__f),

				     std::forward<_Args>(__args)...)),
		    __depend);
	      }
	
	    ~thread()
	    {
	      if (joinable())
		std::terminate();
	    }
	
	    thread(const thread&) = delete;
	
	    thread(thread&& __t) noexcept
	    { swap(__t); }
	
	    thread& operator=(const thread&) = delete;
	
	    thread& operator=(thread&& __t) noexcept
	    {
	      if (joinable())
		std::terminate();
	      swap(__t);
	      return *this;
	    }
	
	    void
	    swap(thread& __t) noexcept
	    { std::swap(_M_id, __t._M_id); }
	
	    bool
	    joinable() const noexcept
	    { return !(_M_id == id()); }
	
	    void
	    join();
	
	    void
	    detach();
	
	    thread::id
	    get_id() const noexcept
	    { return _M_id; }
	
	    /** @pre thread is joinable
	     */
	    native_handle_type
	    native_handle()
	    { return _M_id._M_thread; }
	
	    // Returns a value that hints at the number of hardware thread contexts.
	    static unsigned int
	    hardware_concurrency() noexcept;
	
	  private:
	    template<typename _Callable>
	      struct _State_impl : public _State
	      {
		_Callable		_M_func;
	
		_State_impl(_Callable&& __f) : _M_func(std::forward<_Callable>(__f))
		{ }
	
		void
		_M_run() { _M_func(); }
	      };
	
	    void
	    _M_start_thread(_State_ptr, void (*)());
	
	    template<typename _Callable>
	      static _State_ptr
	      _S_make_state(_Callable&& __f)
	      {
		using _Impl = _State_impl<_Callable>;
		return _State_ptr{new _Impl{std::forward<_Callable>(__f)}};
	      }
	#if _GLIBCXX_THREAD_ABI_COMPAT
	  public:
	    struct _Impl_base;
	    typedef shared_ptr<_Impl_base>	__shared_base_type;
	    struct _Impl_base
	    {
	      __shared_base_type	_M_this_ptr;
	      virtual ~_Impl_base() = default;
	      virtual void _M_run() = 0;
	    };
	
	  private:
	    void
	    _M_start_thread(__shared_base_type, void (*)());
	
	    void
	    _M_start_thread(__shared_base_type);
	#endif
	
	  private:
	    // A call wrapper that does INVOKE(forwarded tuple elements...)
	    template<typename _Tuple>
	      struct _Invoker
	      {
		_Tuple _M_t;
	
		template<typename>
		  struct __result;
		template<typename _Fn, typename... _Args>
		  struct __result<tuple<_Fn, _Args...>>
		  : __invoke_result<_Fn, _Args...>
		  { };
	
		template<size_t... _Ind>
		  typename __result<_Tuple>::type
		  _M_invoke(_Index_tuple<_Ind...>)
		  { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
	

		typename __result<_Tuple>::type
		operator()()
		{
		  using _Indices
		    = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
		  return _M_invoke(_Indices());
		}
	      };
	
	    template<typename... _Tp>
	      using __decayed_tuple = tuple<typename decay<_Tp>::type...>;
	
	  public:
	    // Returns a call wrapper that stores
	    // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
	    template<typename _Callable, typename... _Args>
	      static _Invoker<__decayed_tuple<_Callable, _Args...>>
	      __make_invoker(_Callable&& __callable, _Args&&... __args)

	      {
		return { __decayed_tuple<_Callable, _Args...>{
		    std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
		} };
	      }
	  };
	
	  inline void
	  swap(thread& __x, thread& __y) noexcept
	  { __x.swap(__y); }
	
	  inline bool
	  operator==(thread::id __x, thread::id __y) noexcept
	  {
	    // pthread_equal is undefined if either thread ID is not valid, so we
	    // can't safely use __gthread_equal on default-constructed values (nor
	    // the non-zero value returned by this_thread::get_id() for
	    // single-threaded programs using GNU libc). Assume EqualityComparable.
	    return __x._M_thread == __y._M_thread;
	  }
	
	  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); }
	
	  // DR 889.
	  /// std::hash specialization for thread::id.
	  template<>
	    struct hash<thread::id>
	    : public __hash_base<size_t, thread::id>
	    {
	      size_t
	      operator()(const thread::id& __id) const noexcept
	      { return std::_Hash_impl::hash(__id._M_thread); }
	    };
	
	  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;
	    }
	
	  /** @namespace std::this_thread
	   *  @brief ISO C++ 2011 entities sub-namespace for thread.
	   *  30.3.2 Namespace this_thread.
	   */
	  namespace this_thread
	  {
	    /// get_id
	    inline thread::id
	    get_id() noexcept
	    {
	#ifdef __GLIBC__
	      // For the GNU C library pthread_self() is usable without linking to
	      // libpthread.so but returns 0, so we cannot use it in single-threaded
	      // programs, because this_thread::get_id() != thread::id{} must be true.
	      // We know that pthread_t is an integral type in the GNU C library.
	      if (!__gthread_active_p())
		return thread::id(1);
	#endif
	      return thread::id(__gthread_self());
	    }
	
	    /// yield
	    inline void
	    yield() noexcept
	    {
	#ifdef _GLIBCXX_USE_SCHED_YIELD
	      __gthread_yield();
	#endif
	    }
	
	    void
	    __sleep_for(chrono::seconds, chrono::nanoseconds);
	
	    /// sleep_for
	    template<typename _Rep, typename _Period>
	      inline void
	      sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
	      {
		if (__rtime <= __rtime.zero())
		  return;
		auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
		auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
	#ifdef _GLIBCXX_USE_NANOSLEEP
		__gthread_time_t __ts =
		  {
		    static_cast<std::time_t>(__s.count()),
		    static_cast<long>(__ns.count())
		  };
		while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
		  { }
	#else
		__sleep_for(__s, __ns);
	#endif
	      }
	
	    /// sleep_until
	    template<typename _Clock, typename _Duration>
	      inline void
	      sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
	      {
		auto __now = _Clock::now();
		if (_Clock::is_steady)
		  {
		    if (__now < __atime)
		      sleep_for(__atime - __now);
		    return;
		  }
		while (__now < __atime)
		  {
		    sleep_for(__atime - __now);
		    __now = _Clock::now();
		  }
	      }
	  }
	
	  // @} group threads
	
	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace
	
	#endif // _GLIBCXX_HAS_GTHREADS
	
	#endif // C++11
	
	#endif // _GLIBCXX_THREAD