// std::unique_lock implementation -*- 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 bits/unique_lock.h
	 *  This is an internal header file, included by other library headers.
	 *  Do not attempt to use it directly. @headername{mutex}
	 */
	
	#ifndef _GLIBCXX_UNIQUE_LOCK_H
	#define _GLIBCXX_UNIQUE_LOCK_H 1
	
	#pragma GCC system_header
	
	#if __cplusplus < 201103L
	# include <bits/c++0x_warning.h>
	#else
	
	#include <chrono>
	#include <bits/move.h> // for std::swap
	
	namespace std _GLIBCXX_VISIBILITY(default)
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	
	  /**
	   * @ingroup mutexes
	   * @{
	   */
	
	  /** @brief A movable scoped lock type.
	   *
	   * A unique_lock controls mutex ownership within a scope. Ownership of the
	   * mutex can be delayed until after construction and can be transferred
	   * to another unique_lock by move construction or move assignment. If a
	   * mutex lock is owned when the destructor runs ownership will be released.
	   */
	  template<typename _Mutex>
	    class unique_lock
	    {
	    public:
	      typedef _Mutex mutex_type;
	
	      unique_lock() noexcept
	      : _M_device(0), _M_owns(false)
	      { }
	
	      explicit unique_lock(mutex_type& __m)
	      : _M_device(std::__addressof(__m)), _M_owns(false)
	      {
		lock();
		_M_owns = true;
	      }
	
	      unique_lock(mutex_type& __m, defer_lock_t) noexcept
	      : _M_device(std::__addressof(__m)), _M_owns(false)
	      { }
	
	      unique_lock(mutex_type& __m, try_to_lock_t)
	      : _M_device(std::__addressof(__m)), _M_owns(_M_device->try_lock())
	      { }
	
	      unique_lock(mutex_type& __m, adopt_lock_t) noexcept
	      : _M_device(std::__addressof(__m)), _M_owns(true)
	      {
		// XXX calling thread owns mutex
	      }
	
	      template<typename _Clock, typename _Duration>
		unique_lock(mutex_type& __m,
			    const chrono::time_point<_Clock, _Duration>& __atime)
		: _M_device(std::__addressof(__m)),
		  _M_owns(_M_device->try_lock_until(__atime))
		{ }
	
	      template<typename _Rep, typename _Period>
		unique_lock(mutex_type& __m,
			    const chrono::duration<_Rep, _Period>& __rtime)
		: _M_device(std::__addressof(__m)),
		  _M_owns(_M_device->try_lock_for(__rtime))
		{ }
	
	      ~unique_lock()
	      {
		if (_M_owns)
		  unlock();
	      }
	
	      unique_lock(const unique_lock&) = delete;
	      unique_lock& operator=(const unique_lock&) = delete;
	
	      unique_lock(unique_lock&& __u) noexcept
	      : _M_device(__u._M_device), _M_owns(__u._M_owns)
	      {
		__u._M_device = 0;
		__u._M_owns = false;
	      }
	
	      unique_lock& operator=(unique_lock&& __u) noexcept
	      {
		if(_M_owns)
		  unlock();
	
		unique_lock(std::move(__u)).swap(*this);
	
		__u._M_device = 0;
		__u._M_owns = false;
	
		return *this;
	      }
	
	      void
	      lock()
	      {
		if (!_M_device)
		  __throw_system_error(int(errc::operation_not_permitted));
		else if (_M_owns)
		  __throw_system_error(int(errc::resource_deadlock_would_occur));
		else
		  {

		    _M_device->lock();

		    _M_owns = true;
		  }
	      }
	
	      bool
	      try_lock()
	      {
		if (!_M_device)
		  __throw_system_error(int(errc::operation_not_permitted));
		else if (_M_owns)
		  __throw_system_error(int(errc::resource_deadlock_would_occur));
		else
		  {
		    _M_owns = _M_device->try_lock();
		    return _M_owns;
		  }
	      }
	
	      template<typename _Clock, typename _Duration>
		bool
		try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
		{
		  if (!_M_device)
		    __throw_system_error(int(errc::operation_not_permitted));
		  else if (_M_owns)
		    __throw_system_error(int(errc::resource_deadlock_would_occur));
		  else
		    {
		      _M_owns = _M_device->try_lock_until(__atime);
		      return _M_owns;
		    }
		}
	
	      template<typename _Rep, typename _Period>
		bool
		try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
		{
		  if (!_M_device)
		    __throw_system_error(int(errc::operation_not_permitted));
		  else if (_M_owns)
		    __throw_system_error(int(errc::resource_deadlock_would_occur));
		  else
		    {
		      _M_owns = _M_device->try_lock_for(__rtime);
		      return _M_owns;
		    }
		 }
	
	      void
	      unlock()
	      {

		if (!_M_owns)
		  __throw_system_error(int(errc::operation_not_permitted));

		else if (_M_device)
		  {
		    _M_device->unlock();

		    _M_owns = false;
		  }
	      }
	
	      void
	      swap(unique_lock& __u) noexcept
	      {
		std::swap(_M_device, __u._M_device);
		std::swap(_M_owns, __u._M_owns);
	      }
	
	      mutex_type*
	      release() noexcept
	      {
		mutex_type* __ret = _M_device;
		_M_device = 0;
		_M_owns = false;
		return __ret;
	      }
	
	      bool
	      owns_lock() const noexcept
	      { return _M_owns; }
	
	      explicit operator bool() const noexcept
	      { return owns_lock(); }
	
	      mutex_type*
	      mutex() const noexcept
	      { return _M_device; }
	
	    private:
	      mutex_type*	_M_device;
	      bool		_M_owns;
	    };
	
	  /// Swap overload for unique_lock objects.
	  template<typename _Mutex>
	    inline void
	    swap(unique_lock<_Mutex>& __x, unique_lock<_Mutex>& __y) noexcept
	    { __x.swap(__y); }
	
	  // @} group mutexes
	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace
	
	#endif // C++11
	#endif // _GLIBCXX_UNIQUE_LOCK_H