// <mutex> -*- C++ -*-
	
	// Copyright (C) 2003-2019 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/mutex
	 *  This is a Standard C++ Library header.
	 */
	
	#ifndef _GLIBCXX_MUTEX
	#define _GLIBCXX_MUTEX 1
	
	#pragma GCC system_header
	
	#if __cplusplus < 201103L
	# include <bits/c++0x_warning.h>
	#else
	
	#include <tuple>
	#include <chrono>
	#include <exception>
	#include <type_traits>
	#include <system_error>
	#include <bits/std_mutex.h>
	#include <bits/unique_lock.h>
	#if ! _GTHREAD_USE_MUTEX_TIMEDLOCK
	# include <condition_variable>
	# include <thread>
	#endif
	#ifndef _GLIBCXX_HAVE_TLS
	# include <bits/std_function.h>
	#endif
	
	namespace std _GLIBCXX_VISIBILITY(default)
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	
	  /**
	   * @ingroup mutexes
	   * @{
	   */
	
	#ifdef _GLIBCXX_HAS_GTHREADS
	
	  // Common base class for std::recursive_mutex and std::recursive_timed_mutex
	  class __recursive_mutex_base
	  {
	  protected:
	    typedef __gthread_recursive_mutex_t		__native_type;
	
	    __recursive_mutex_base(const __recursive_mutex_base&) = delete;
	    __recursive_mutex_base& operator=(const __recursive_mutex_base&) = delete;
	
	#ifdef __GTHREAD_RECURSIVE_MUTEX_INIT
	    __native_type  _M_mutex = __GTHREAD_RECURSIVE_MUTEX_INIT;
	
	    __recursive_mutex_base() = default;
	#else
	    __native_type  _M_mutex;
	
	    __recursive_mutex_base()
	    {
	      // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
	      __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION(&_M_mutex);
	    }
	
	    ~__recursive_mutex_base()
	    { __gthread_recursive_mutex_destroy(&_M_mutex); }
	#endif
	  };
	
	  /// The standard recursive mutex type.
	  class recursive_mutex : private __recursive_mutex_base
	  {
	  public:
	    typedef __native_type* 			native_handle_type;
	
	    recursive_mutex() = default;
	    ~recursive_mutex() = default;
	
	    recursive_mutex(const recursive_mutex&) = delete;
	    recursive_mutex& operator=(const recursive_mutex&) = delete;
	
	    void
	    lock()
	    {
	      int __e = __gthread_recursive_mutex_lock(&_M_mutex);
	
	      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
	      if (__e)
		__throw_system_error(__e);
	    }
	
	    bool
	    try_lock() noexcept
	    {
	      // XXX EINVAL, EAGAIN, EBUSY
	      return !__gthread_recursive_mutex_trylock(&_M_mutex);
	    }
	
	    void
	    unlock()
	    {
	      // XXX EINVAL, EAGAIN, EBUSY
	      __gthread_recursive_mutex_unlock(&_M_mutex);
	    }
	
	    native_handle_type
	    native_handle() noexcept
	    { return &_M_mutex; }
	  };
	
	#if _GTHREAD_USE_MUTEX_TIMEDLOCK
	  template<typename _Derived>
	    class __timed_mutex_impl
	    {
	    protected:
	      typedef chrono::high_resolution_clock 	__clock_t;
	
	      template<typename _Rep, typename _Period>
		bool
		_M_try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
		{
		  using chrono::steady_clock;
		  auto __rt = chrono::duration_cast<steady_clock::duration>(__rtime);
		  if (ratio_greater<steady_clock::period, _Period>())
		    ++__rt;
		  return _M_try_lock_until(steady_clock::now() + __rt);
		}
	
	      template<typename _Duration>
		bool
		_M_try_lock_until(const chrono::time_point<__clock_t,
							   _Duration>& __atime)
		{
		  auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
		  auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
	
		  __gthread_time_t __ts = {
		    static_cast<std::time_t>(__s.time_since_epoch().count()),
		    static_cast<long>(__ns.count())
		  };
	
		  return static_cast<_Derived*>(this)->_M_timedlock(__ts);
		}
	
	      template<typename _Clock, typename _Duration>
		bool
		_M_try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
		{
		  auto __rtime = __atime - _Clock::now();
		  return _M_try_lock_until(__clock_t::now() + __rtime);
		}
	    };
	
	  /// The standard timed mutex type.
	  class timed_mutex
	  : private __mutex_base, public __timed_mutex_impl<timed_mutex>
	  {
	  public:
	    typedef __native_type* 		  	native_handle_type;
	
	    timed_mutex() = default;
	    ~timed_mutex() = default;
	
	    timed_mutex(const timed_mutex&) = delete;
	    timed_mutex& operator=(const timed_mutex&) = delete;
	
	    void
	    lock()
	    {
	      int __e = __gthread_mutex_lock(&_M_mutex);
	
	      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
	      if (__e)
		__throw_system_error(__e);
	    }
	
	    bool
	    try_lock() noexcept
	    {
	      // XXX EINVAL, EAGAIN, EBUSY
	      return !__gthread_mutex_trylock(&_M_mutex);
	    }
	
	    template <class _Rep, class _Period>
	      bool
	      try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
	      { return _M_try_lock_for(__rtime); }
	
	    template <class _Clock, class _Duration>
	      bool
	      try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
	      { return _M_try_lock_until(__atime); }
	
	    void
	    unlock()
	    {
	      // XXX EINVAL, EAGAIN, EBUSY
	      __gthread_mutex_unlock(&_M_mutex);
	    }
	
	    native_handle_type
	    native_handle() noexcept
	    { return &_M_mutex; }
	
	    private:
	      friend class __timed_mutex_impl<timed_mutex>;
	
	      bool
	      _M_timedlock(const __gthread_time_t& __ts)
	      { return !__gthread_mutex_timedlock(&_M_mutex, &__ts); }
	  };
	
	  /// recursive_timed_mutex
	  class recursive_timed_mutex
	  : private __recursive_mutex_base,
	    public __timed_mutex_impl<recursive_timed_mutex>
	  {
	  public:
	    typedef __native_type* 			native_handle_type;
	
	    recursive_timed_mutex() = default;
	    ~recursive_timed_mutex() = default;
	
	    recursive_timed_mutex(const recursive_timed_mutex&) = delete;
	    recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;
	
	    void
	    lock()
	    {
	      int __e = __gthread_recursive_mutex_lock(&_M_mutex);
	
	      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
	      if (__e)
		__throw_system_error(__e);
	    }
	
	    bool
	    try_lock() noexcept
	    {
	      // XXX EINVAL, EAGAIN, EBUSY
	      return !__gthread_recursive_mutex_trylock(&_M_mutex);
	    }
	
	    template <class _Rep, class _Period>
	      bool
	      try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
	      { return _M_try_lock_for(__rtime); }
	
	    template <class _Clock, class _Duration>
	      bool
	      try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
	      { return _M_try_lock_until(__atime); }
	
	    void
	    unlock()
	    {
	      // XXX EINVAL, EAGAIN, EBUSY
	      __gthread_recursive_mutex_unlock(&_M_mutex);
	    }
	
	    native_handle_type
	    native_handle() noexcept
	    { return &_M_mutex; }
	
	    private:
	      friend class __timed_mutex_impl<recursive_timed_mutex>;
	
	      bool
	      _M_timedlock(const __gthread_time_t& __ts)
	      { return !__gthread_recursive_mutex_timedlock(&_M_mutex, &__ts); }
	  };
	
	#else // !_GTHREAD_USE_MUTEX_TIMEDLOCK
	
	  /// timed_mutex
	  class timed_mutex
	  {
	    mutex		_M_mut;
	    condition_variable	_M_cv;
	    bool		_M_locked = false;
	
	  public:
	
	    timed_mutex() = default;
	    ~timed_mutex() { __glibcxx_assert( !_M_locked ); }
	
	    timed_mutex(const timed_mutex&) = delete;
	    timed_mutex& operator=(const timed_mutex&) = delete;
	
	    void
	    lock()
	    {
	      unique_lock<mutex> __lk(_M_mut);
	      _M_cv.wait(__lk, [&]{ return !_M_locked; });
	      _M_locked = true;
	    }
	
	    bool
	    try_lock()
	    {
	      lock_guard<mutex> __lk(_M_mut);
	      if (_M_locked)
		return false;
	      _M_locked = true;
	      return true;
	    }
	
	    template<typename _Rep, typename _Period>
	      bool
	      try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
	      {
		unique_lock<mutex> __lk(_M_mut);
		if (!_M_cv.wait_for(__lk, __rtime, [&]{ return !_M_locked; }))
		  return false;
		_M_locked = true;
		return true;
	      }
	
	    template<typename _Clock, typename _Duration>
	      bool
	      try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
	      {
		unique_lock<mutex> __lk(_M_mut);
		if (!_M_cv.wait_until(__lk, __atime, [&]{ return !_M_locked; }))
		  return false;
		_M_locked = true;
		return true;
	      }
	
	    void
	    unlock()
	    {
	      lock_guard<mutex> __lk(_M_mut);
	      __glibcxx_assert( _M_locked );
	      _M_locked = false;
	      _M_cv.notify_one();
	    }
	  };
	
	  /// recursive_timed_mutex
	  class recursive_timed_mutex
	  {
	    mutex		_M_mut;
	    condition_variable	_M_cv;
	    thread::id		_M_owner;
	    unsigned		_M_count = 0;
	
	    // Predicate type that tests whether the current thread can lock a mutex.
	    struct _Can_lock
	    {
	      // Returns true if the mutex is unlocked or is locked by _M_caller.
	      bool
	      operator()() const noexcept
	      { return _M_mx->_M_count == 0 || _M_mx->_M_owner == _M_caller; }
	
	      const recursive_timed_mutex* _M_mx;
	      thread::id _M_caller;
	    };
	
	  public:
	
	    recursive_timed_mutex() = default;
	    ~recursive_timed_mutex() { __glibcxx_assert( _M_count == 0 ); }
	
	    recursive_timed_mutex(const recursive_timed_mutex&) = delete;
	    recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;
	
	    void
	    lock()
	    {
	      auto __id = this_thread::get_id();
	      _Can_lock __can_lock{this, __id};
	      unique_lock<mutex> __lk(_M_mut);
	      _M_cv.wait(__lk, __can_lock);
	      if (_M_count == -1u)
		__throw_system_error(EAGAIN); // [thread.timedmutex.recursive]/3
	      _M_owner = __id;
	      ++_M_count;
	    }
	
	    bool
	    try_lock()
	    {
	      auto __id = this_thread::get_id();
	      _Can_lock __can_lock{this, __id};
	      lock_guard<mutex> __lk(_M_mut);
	      if (!__can_lock())
		return false;
	      if (_M_count == -1u)
		return false;
	      _M_owner = __id;
	      ++_M_count;
	      return true;
	    }
	
	    template<typename _Rep, typename _Period>
	      bool
	      try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
	      {
		auto __id = this_thread::get_id();
		_Can_lock __can_lock{this, __id};
		unique_lock<mutex> __lk(_M_mut);
		if (!_M_cv.wait_for(__lk, __rtime, __can_lock))
		  return false;
		if (_M_count == -1u)
		  return false;
		_M_owner = __id;
		++_M_count;
		return true;
	      }
	
	    template<typename _Clock, typename _Duration>
	      bool
	      try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
	      {
		auto __id = this_thread::get_id();
		_Can_lock __can_lock{this, __id};
		unique_lock<mutex> __lk(_M_mut);
		if (!_M_cv.wait_until(__lk, __atime, __can_lock))
		  return false;
		if (_M_count == -1u)
		  return false;
		_M_owner = __id;
		++_M_count;
		return true;
	      }
	
	    void
	    unlock()
	    {
	      lock_guard<mutex> __lk(_M_mut);
	      __glibcxx_assert( _M_owner == this_thread::get_id() );
	      __glibcxx_assert( _M_count > 0 );
	      if (--_M_count == 0)
		{
		  _M_owner = {};
		  _M_cv.notify_one();
		}
	    }
	  };
	
	#endif
	#endif // _GLIBCXX_HAS_GTHREADS
	
	  template<typename _Lock>
	    inline unique_lock<_Lock>
	    __try_to_lock(_Lock& __l)
	    { return unique_lock<_Lock>{__l, try_to_lock}; }
	
	  template<int _Idx, bool _Continue = true>
	    struct __try_lock_impl
	    {
	      template<typename... _Lock>
		static void
		__do_try_lock(tuple<_Lock&...>& __locks, int& __idx)
		{
	          __idx = _Idx;
	          auto __lock = std::__try_to_lock(std::get<_Idx>(__locks));
	          if (__lock.owns_lock())
	            {
		      constexpr bool __cont = _Idx + 2 < sizeof...(_Lock);
		      using __try_locker = __try_lock_impl<_Idx + 1, __cont>;
		      __try_locker::__do_try_lock(__locks, __idx);
	              if (__idx == -1)
	                __lock.release();
	            }
		}
	    };
	
	  template<int _Idx>
	    struct __try_lock_impl<_Idx, false>
	    {
	      template<typename... _Lock>
		static void
		__do_try_lock(tuple<_Lock&...>& __locks, int& __idx)
		{
	          __idx = _Idx;
	          auto __lock = std::__try_to_lock(std::get<_Idx>(__locks));
	          if (__lock.owns_lock())
	            {
	              __idx = -1;
	              __lock.release();
	            }
		}
	    };
	
	  /** @brief Generic try_lock.
	   *  @param __l1 Meets Lockable requirements (try_lock() may throw).
	   *  @param __l2 Meets Lockable requirements (try_lock() may throw).
	   *  @param __l3 Meets Lockable requirements (try_lock() may throw).
	   *  @return Returns -1 if all try_lock() calls return true. Otherwise returns
	   *          a 0-based index corresponding to the argument that returned false.
	   *  @post Either all arguments are locked, or none will be.
	   *
	   *  Sequentially calls try_lock() on each argument.
	   */
	  template<typename _Lock1, typename _Lock2, typename... _Lock3>
	    int
	    try_lock(_Lock1& __l1, _Lock2& __l2, _Lock3&... __l3)
	    {
	      int __idx;
	      auto __locks = std::tie(__l1, __l2, __l3...);
	      __try_lock_impl<0>::__do_try_lock(__locks, __idx);
	      return __idx;
	    }
	
	  /** @brief Generic lock.
	   *  @param __l1 Meets Lockable requirements (try_lock() may throw).
	   *  @param __l2 Meets Lockable requirements (try_lock() may throw).
	   *  @param __l3 Meets Lockable requirements (try_lock() may throw).
	   *  @throw An exception thrown by an argument's lock() or try_lock() member.
	   *  @post All arguments are locked.
	   *
	   *  All arguments are locked via a sequence of calls to lock(), try_lock()
	   *  and unlock().  If the call exits via an exception any locks that were
	   *  obtained will be released.
	   */
	  template<typename _L1, typename _L2, typename... _L3>
	    void
	    lock(_L1& __l1, _L2& __l2, _L3&... __l3)
	    {
	      while (true)
	        {
	          using __try_locker = __try_lock_impl<0, sizeof...(_L3) != 0>;
	          unique_lock<_L1> __first(__l1);
	          int __idx;
	          auto __locks = std::tie(__l2, __l3...);
	          __try_locker::__do_try_lock(__locks, __idx);
	          if (__idx == -1)
	            {
	              __first.release();
	              return;
	            }
	        }
	    }
	
	#if __cplusplus >= 201703L
	#define __cpp_lib_scoped_lock 201703
	  /** @brief A scoped lock type for multiple lockable objects.
	   *
	   * A scoped_lock controls mutex ownership within a scope, releasing
	   * ownership in the destructor.
	   */
	  template<typename... _MutexTypes>
	    class scoped_lock
	    {
	    public:
	      explicit scoped_lock(_MutexTypes&... __m) : _M_devices(std::tie(__m...))
	      { std::lock(__m...); }
	
	      explicit scoped_lock(adopt_lock_t, _MutexTypes&... __m) noexcept
	      : _M_devices(std::tie(__m...))
	      { } // calling thread owns mutex
	
	      ~scoped_lock()
	      {
		std::apply([](_MutexTypes&... __m) {
		  char __i[] __attribute__((__unused__)) = { (__m.unlock(), 0)... };
		}, _M_devices);
	      }
	
	      scoped_lock(const scoped_lock&) = delete;
	      scoped_lock& operator=(const scoped_lock&) = delete;
	
	    private:
	      tuple<_MutexTypes&...> _M_devices;
	    };
	
	  template<>
	    class scoped_lock<>
	    {
	    public:
	      explicit scoped_lock() = default;
	      explicit scoped_lock(adopt_lock_t) noexcept { }
	      ~scoped_lock() = default;
	
	      scoped_lock(const scoped_lock&) = delete;
	      scoped_lock& operator=(const scoped_lock&) = delete;
	    };
	
	  template<typename _Mutex>
	    class scoped_lock<_Mutex>
	    {
	    public:
	      using mutex_type = _Mutex;
	
	      explicit scoped_lock(mutex_type& __m) : _M_device(__m)
	      { _M_device.lock(); }
	
	      explicit scoped_lock(adopt_lock_t, mutex_type& __m) noexcept
	      : _M_device(__m)
	      { } // calling thread owns mutex
	

	      ~scoped_lock()

	      { _M_device.unlock(); }
	
	      scoped_lock(const scoped_lock&) = delete;
	      scoped_lock& operator=(const scoped_lock&) = delete;
	
	    private:
	      mutex_type&  _M_device;
	    };
	#endif // C++17
	
	#ifdef _GLIBCXX_HAS_GTHREADS
	  /// once_flag
	  struct once_flag
	  {
	  private:
	    typedef __gthread_once_t __native_type;
	    __native_type  _M_once = __GTHREAD_ONCE_INIT;
	
	  public:
	    /// Constructor
	    constexpr once_flag() noexcept = default;
	
	    /// Deleted copy constructor
	    once_flag(const once_flag&) = delete;
	    /// Deleted assignment operator
	    once_flag& operator=(const once_flag&) = delete;
	
	    template<typename _Callable, typename... _Args>
	      friend void
	      call_once(once_flag& __once, _Callable&& __f, _Args&&... __args);
	  };
	
	#ifdef _GLIBCXX_HAVE_TLS
	  extern __thread void* __once_callable;
	  extern __thread void (*__once_call)();
	#else
	  extern function<void()> __once_functor;
	
	  extern void
	  __set_once_functor_lock_ptr(unique_lock<mutex>*);
	
	  extern mutex&
	  __get_once_mutex();
	#endif
	
	  extern "C" void __once_proxy(void);
	
	  /// call_once
	  template<typename _Callable, typename... _Args>
	    void
	    call_once(once_flag& __once, _Callable&& __f, _Args&&... __args)
	    {
	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
	      // 2442. call_once() shouldn't DECAY_COPY()
	      auto __callable = [&] {
		  std::__invoke(std::forward<_Callable>(__f),
				std::forward<_Args>(__args)...);
	      };
	#ifdef _GLIBCXX_HAVE_TLS
	      __once_callable = std::__addressof(__callable);
	      __once_call = []{ (*(decltype(__callable)*)__once_callable)(); };
	#else
	      unique_lock<mutex> __functor_lock(__get_once_mutex());
	      __once_functor = __callable;
	      __set_once_functor_lock_ptr(&__functor_lock);
	#endif
	
	      int __e = __gthread_once(&__once._M_once, &__once_proxy);
	
	#ifndef _GLIBCXX_HAVE_TLS
	      if (__functor_lock)
	        __set_once_functor_lock_ptr(0);
	#endif
	
	#ifdef __clang_analyzer__
	      // PR libstdc++/82481
	      __once_callable = nullptr;
	      __once_call = nullptr;
	#endif
	
	      if (__e)
		__throw_system_error(__e);
	    }
	#endif // _GLIBCXX_HAS_GTHREADS
	
	  // @} group mutexes
	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace
	
	#endif // C++11
	
	#endif // _GLIBCXX_MUTEX