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/usr/include/c++/11/condition_variable


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     1	// <condition_variable> -*- C++ -*-
     2	
     3	// Copyright (C) 2008-2021 Free Software Foundation, Inc.
     4	//
     5	// This file is part of the GNU ISO C++ Library.  This library is free
     6	// software; you can redistribute it and/or modify it under the
     7	// terms of the GNU General Public License as published by the
     8	// Free Software Foundation; either version 3, or (at your option)
     9	// any later version.
    10	
    11	// This library is distributed in the hope that it will be useful,
    12	// but WITHOUT ANY WARRANTY; without even the implied warranty of
    13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    14	// GNU General Public License for more details.
    15	
    16	// Under Section 7 of GPL version 3, you are granted additional
    17	// permissions described in the GCC Runtime Library Exception, version
    18	// 3.1, as published by the Free Software Foundation.
    19	
    20	// You should have received a copy of the GNU General Public License and
    21	// a copy of the GCC Runtime Library Exception along with this program;
    22	// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    23	// <http://www.gnu.org/licenses/>.
    24	
    25	/** @file include/condition_variable
    26	 *  This is a Standard C++ Library header.
    27	 */
    28	
    29	#ifndef _GLIBCXX_CONDITION_VARIABLE
    30	#define _GLIBCXX_CONDITION_VARIABLE 1
    31	
    32	#pragma GCC system_header
    33	
    34	#if __cplusplus < 201103L
    35	# include <bits/c++0x_warning.h>
    36	#else
    37	
    38	#include <chrono>
    39	
    40	#include <bits/std_mutex.h>
    41	#include <bits/unique_lock.h>
    42	#include <bits/alloc_traits.h>
    43	#include <bits/shared_ptr.h>
    44	#include <bits/cxxabi_forced.h>
    45	
    46	#if __cplusplus > 201703L
    47	# include <stop_token>
    48	#endif
    49	
    50	#if defined(_GLIBCXX_HAS_GTHREADS)
    51	
    52	namespace std _GLIBCXX_VISIBILITY(default)
    53	{
    54	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    55	
    56	  /**
    57	   * @defgroup condition_variables Condition Variables
    58	   * @ingroup concurrency
    59	   *
    60	   * Classes for condition_variable support.
    61	   * @{
    62	   */
    63	
    64	  /// cv_status
    65	  enum class cv_status { no_timeout, timeout };
    66	
    67	  /// condition_variable
    68	  class condition_variable
    69	  {
    70	    using steady_clock = chrono::steady_clock;
    71	    using system_clock = chrono::system_clock;
    72	#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
    73	    using __clock_t = steady_clock;
    74	#else
    75	    using __clock_t = system_clock;
    76	#endif
    77	
    78	    __condvar _M_cond;
    79	
    80	  public:
    81	    typedef __gthread_cond_t* 		native_handle_type;
    82	
    83	    condition_variable() noexcept;
    84	    ~condition_variable() noexcept;
    85	
    86	    condition_variable(const condition_variable&) = delete;
    87	    condition_variable& operator=(const condition_variable&) = delete;
    88	
    89	    void
    90	    notify_one() noexcept;
    91	
    92	    void
    93	    notify_all() noexcept;
    94	
    95	    void
    96	    wait(unique_lock<mutex>& __lock) noexcept;
    97	
    98	    template<typename _Predicate>
    99	      void
   100	      wait(unique_lock<mutex>& __lock, _Predicate __p)
   101	      {
   102		while (!__p())
   103		  wait(__lock);
   104	      }
   105	
   106	#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
   107	    template<typename _Duration>
   108	      cv_status
   109	      wait_until(unique_lock<mutex>& __lock,
   110			 const chrono::time_point<steady_clock, _Duration>& __atime)
   111	      { return __wait_until_impl(__lock, __atime); }
   112	#endif
   113	
   114	    template<typename _Duration>
   115	      cv_status
   116	      wait_until(unique_lock<mutex>& __lock,
   117			 const chrono::time_point<system_clock, _Duration>& __atime)
   118	      { return __wait_until_impl(__lock, __atime); }
   119	
   120	    template<typename _Clock, typename _Duration>
   121	      cv_status
   122	      wait_until(unique_lock<mutex>& __lock,
   123			 const chrono::time_point<_Clock, _Duration>& __atime)
   124	      {
   125	#if __cplusplus > 201703L
   126		static_assert(chrono::is_clock_v<_Clock>);
   127	#endif
   128		using __s_dur = typename __clock_t::duration;
   129		const typename _Clock::time_point __c_entry = _Clock::now();
   130		const __clock_t::time_point __s_entry = __clock_t::now();
   131		const auto __delta = __atime - __c_entry;
   132		const auto __s_atime = __s_entry +
   133		  chrono::__detail::ceil<__s_dur>(__delta);
   134	
   135		if (__wait_until_impl(__lock, __s_atime) == cv_status::no_timeout)
   136		  return cv_status::no_timeout;
   137		// We got a timeout when measured against __clock_t but
   138		// we need to check against the caller-supplied clock
   139		// to tell whether we should return a timeout.
   140		if (_Clock::now() < __atime)
   141		  return cv_status::no_timeout;
   142		return cv_status::timeout;
   143	      }
   144	
   145	    template<typename _Clock, typename _Duration, typename _Predicate>
   146	      bool
   147	      wait_until(unique_lock<mutex>& __lock,
   148			 const chrono::time_point<_Clock, _Duration>& __atime,
   149			 _Predicate __p)
   150	      {
   151		while (!__p())
   152		  if (wait_until(__lock, __atime) == cv_status::timeout)
   153		    return __p();
   154		return true;
   155	      }
   156	
   157	    template<typename _Rep, typename _Period>
   158	      cv_status
   159	      wait_for(unique_lock<mutex>& __lock,
   160		       const chrono::duration<_Rep, _Period>& __rtime)
   161	      {
   162		using __dur = typename steady_clock::duration;
   163		return wait_until(__lock,
   164				  steady_clock::now() +
   165				  chrono::__detail::ceil<__dur>(__rtime));
   166	      }
   167	
   168	    template<typename _Rep, typename _Period, typename _Predicate>
   169	      bool
   170	      wait_for(unique_lock<mutex>& __lock,
   171		       const chrono::duration<_Rep, _Period>& __rtime,
   172		       _Predicate __p)
   173	      {
   174		using __dur = typename steady_clock::duration;
   175		return wait_until(__lock,
   176				  steady_clock::now() +
   177				  chrono::__detail::ceil<__dur>(__rtime),
   178				  std::move(__p));
   179	      }
   180	
   181	    native_handle_type
   182	    native_handle()
   183	    { return _M_cond.native_handle(); }
   184	
   185	  private:
   186	#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
   187	    template<typename _Dur>
   188	      cv_status
   189	      __wait_until_impl(unique_lock<mutex>& __lock,
   190				const chrono::time_point<steady_clock, _Dur>& __atime)
   191	      {
   192		auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
   193		auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
   194	
   195		__gthread_time_t __ts =
   196		  {
   197		    static_cast<std::time_t>(__s.time_since_epoch().count()),
   198		    static_cast<long>(__ns.count())
   199		  };
   200	
   201		_M_cond.wait_until(*__lock.mutex(), CLOCK_MONOTONIC, __ts);
   202	
   203		return (steady_clock::now() < __atime
   204			? cv_status::no_timeout : cv_status::timeout);
   205	      }
   206	#endif
   207	
   208	    template<typename _Dur>
   209	      cv_status
   210	      __wait_until_impl(unique_lock<mutex>& __lock,
   211				const chrono::time_point<system_clock, _Dur>& __atime)
   212	      {
   213		auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
   214		auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
   215	
   216		__gthread_time_t __ts =
   217		  {
   218		    static_cast<std::time_t>(__s.time_since_epoch().count()),
   219		    static_cast<long>(__ns.count())
   220		  };
   221	
   222		_M_cond.wait_until(*__lock.mutex(), __ts);
   223	
   224		return (system_clock::now() < __atime
   225			? cv_status::no_timeout : cv_status::timeout);
   226	      }
   227	  };
   228	
   229	  void
   230	  notify_all_at_thread_exit(condition_variable&, unique_lock<mutex>);
   231	
   232	  struct __at_thread_exit_elt
   233	  {
   234	    __at_thread_exit_elt* _M_next;
   235	    void (*_M_cb)(void*);
   236	  };
   237	
   238	  inline namespace _V2 {
   239	
   240	  /// condition_variable_any
   241	  // Like above, but mutex is not required to have try_lock.
   242	  class condition_variable_any
   243	  {
   244	#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
   245	    using __clock_t = chrono::steady_clock;
   246	#else
   247	    using __clock_t = chrono::system_clock;
   248	#endif
   249	    condition_variable			_M_cond;
   250	    shared_ptr<mutex>			_M_mutex;
   251	
   252	    // scoped unlock - unlocks in ctor, re-locks in dtor
   253	    template<typename _Lock>
   254	      struct _Unlock
   255	      {
   256		explicit _Unlock(_Lock& __lk) : _M_lock(__lk) { __lk.unlock(); }
   257	
   258	#pragma GCC diagnostic push
   259	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
   260		~_Unlock() noexcept(false)
   261		{
   262		  if (uncaught_exception())
   263		    {
   264		      __try
   265		      { _M_lock.lock(); }
   266		      __catch(const __cxxabiv1::__forced_unwind&)
   267		      { __throw_exception_again; }
   268		      __catch(...)
   269		      { }
   270		    }
   271		  else
   272		    _M_lock.lock();
   273		}
   274	#pragma GCC diagnostic pop
   275	
   276		_Unlock(const _Unlock&) = delete;
   277		_Unlock& operator=(const _Unlock&) = delete;
   278	
   279		_Lock& _M_lock;
   280	      };
   281	
   282	  public:
   283	    condition_variable_any() : _M_mutex(std::make_shared<mutex>()) { }
   284	    ~condition_variable_any() = default;
   285	
   286	    condition_variable_any(const condition_variable_any&) = delete;
   287	    condition_variable_any& operator=(const condition_variable_any&) = delete;
   288	
   289	    void
   290	    notify_one() noexcept
   291	    {
   292	      lock_guard<mutex> __lock(*_M_mutex);
   293	      _M_cond.notify_one();
   294	    }
   295	
   296	    void
   297	    notify_all() noexcept
   298	    {
   299	      lock_guard<mutex> __lock(*_M_mutex);
   300	      _M_cond.notify_all();
   301	    }
   302	
   303	    template<typename _Lock>
   304	      void
   305	      wait(_Lock& __lock)
   306	      {
   307		shared_ptr<mutex> __mutex = _M_mutex;
   308		unique_lock<mutex> __my_lock(*__mutex);
   309		_Unlock<_Lock> __unlock(__lock);
   310		// *__mutex must be unlocked before re-locking __lock so move
   311		// ownership of *__mutex lock to an object with shorter lifetime.
   312		unique_lock<mutex> __my_lock2(std::move(__my_lock));
   313		_M_cond.wait(__my_lock2);
   314	      }
   315	
   316	
   317	    template<typename _Lock, typename _Predicate>
   318	      void
   319	      wait(_Lock& __lock, _Predicate __p)
   320	      {
   321		while (!__p())
   322		  wait(__lock);
   323	      }
   324	
   325	    template<typename _Lock, typename _Clock, typename _Duration>
   326	      cv_status
   327	      wait_until(_Lock& __lock,
   328			 const chrono::time_point<_Clock, _Duration>& __atime)
   329	      {
   330		shared_ptr<mutex> __mutex = _M_mutex;
   331		unique_lock<mutex> __my_lock(*__mutex);
   332		_Unlock<_Lock> __unlock(__lock);
   333		// *__mutex must be unlocked before re-locking __lock so move
   334		// ownership of *__mutex lock to an object with shorter lifetime.
   335		unique_lock<mutex> __my_lock2(std::move(__my_lock));
   336		return _M_cond.wait_until(__my_lock2, __atime);
   337	      }
   338	
   339	    template<typename _Lock, typename _Clock,
   340		     typename _Duration, typename _Predicate>
   341	      bool
   342	      wait_until(_Lock& __lock,
   343			 const chrono::time_point<_Clock, _Duration>& __atime,
   344			 _Predicate __p)
   345	      {
   346		while (!__p())
   347		  if (wait_until(__lock, __atime) == cv_status::timeout)
   348		    return __p();
   349		return true;
   350	      }
   351	
   352	    template<typename _Lock, typename _Rep, typename _Period>
   353	      cv_status
   354	      wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime)
   355	      { return wait_until(__lock, __clock_t::now() + __rtime); }
   356	
   357	    template<typename _Lock, typename _Rep,
   358		     typename _Period, typename _Predicate>
   359	      bool
   360	      wait_for(_Lock& __lock,
   361		       const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
   362	      { return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
   363	
   364	#ifdef __cpp_lib_jthread
   365	    template <class _Lock, class _Predicate>
   366	    bool wait(_Lock& __lock,
   367	              stop_token __stoken,
   368	              _Predicate __p)
   369	    {
   370	      if (__stoken.stop_requested())
   371	        {
   372	          return __p();
   373	        }
   374	 
   375	      std::stop_callback __cb(__stoken, [this] { notify_all(); });
   376	      shared_ptr<mutex> __mutex = _M_mutex;
   377	      while (!__p())
   378	        {
   379	          unique_lock<mutex> __my_lock(*__mutex);
   380	          if (__stoken.stop_requested())
   381	            {
   382	              return false;
   383	            }
   384	          // *__mutex must be unlocked before re-locking __lock so move
   385	          // ownership of *__mutex lock to an object with shorter lifetime.
   386	          _Unlock<_Lock> __unlock(__lock);
   387	          unique_lock<mutex> __my_lock2(std::move(__my_lock));
   388	          _M_cond.wait(__my_lock2);
   389	        }
   390	      return true;
   391	    }
   392	
   393	    template <class _Lock, class _Clock, class _Duration, class _Predicate>
   394	    bool wait_until(_Lock& __lock,
   395	                    stop_token __stoken,
   396	                    const chrono::time_point<_Clock, _Duration>& __abs_time,
   397	                    _Predicate __p)
   398	    {
   399	      if (__stoken.stop_requested())
   400	        {
   401	          return __p();
   402	        }
   403	
   404	      std::stop_callback __cb(__stoken, [this] { notify_all(); });
   405	      shared_ptr<mutex> __mutex = _M_mutex;
   406	      while (!__p())
   407	        {
   408	          bool __stop;
   409	          {
   410	            unique_lock<mutex> __my_lock(*__mutex);
   411	            if (__stoken.stop_requested())
   412	              {
   413	                return false;
   414	              }
   415	            _Unlock<_Lock> __u(__lock);
   416	            unique_lock<mutex> __my_lock2(std::move(__my_lock));
   417	            const auto __status = _M_cond.wait_until(__my_lock2, __abs_time);
   418	            __stop = (__status == std::cv_status::timeout) || __stoken.stop_requested();
   419	          }
   420	          if (__stop)
   421	            {
   422	              return __p();
   423	            }
   424	        }
   425	      return true;
   426	    }
   427	
   428	    template <class _Lock, class _Rep, class _Period, class _Predicate>
   429	    bool wait_for(_Lock& __lock,
   430	                  stop_token __stoken,
   431	                  const chrono::duration<_Rep, _Period>& __rel_time,
   432	                  _Predicate __p)
   433	    {
   434	      auto __abst = std::chrono::steady_clock::now() + __rel_time;
   435	      return wait_until(__lock,
   436	                        std::move(__stoken),
   437	                        __abst,
   438	                        std::move(__p));
   439	    }
   440	#endif
   441	  };
   442	
   443	  } // end inline namespace
   444	
   445	  /// @} group condition_variables
   446	_GLIBCXX_END_NAMESPACE_VERSION
   447	} // namespace
   448	
   449	#endif // _GLIBCXX_HAS_GTHREADS
   450	#endif // C++11
   451	#endif // _GLIBCXX_CONDITION_VARIABLE