Home | History | Annotate | Line # | Download | only in std 
      1 // <semaphore> -*- C++ -*-
      2 
      3 // Copyright (C) 2020-2024 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/semaphore
     26  *  This is a Standard C++ Library header.
     27  */
     28 
     29 #ifndef _GLIBCXX_SEMAPHORE
     30 #define _GLIBCXX_SEMAPHORE 1
     31 
     32 #pragma GCC system_header
     33 
     34 #include <bits/requires_hosted.h> // concurrency
     35 
     36 #if __cplusplus > 201703L
     37 #include <bits/semaphore_base.h>
     38 
     39 #define __glibcxx_want_semaphore
     40 #include <bits/version.h>
     41 
     42 #ifdef __cpp_lib_semaphore // C++ >= 20 && hosted && (atomic_wait || posix_sem)
     43 namespace std _GLIBCXX_VISIBILITY(default)
     44 {
     45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     46 
     47   template<ptrdiff_t __least_max_value = __semaphore_impl::_S_max>
     48     class counting_semaphore
     49     {
     50       static_assert(__least_max_value >= 0);
     51       static_assert(__least_max_value <= __semaphore_impl::_S_max);
     52 
     53       __semaphore_impl _M_sem;
     54 
     55     public:
     56       explicit counting_semaphore(ptrdiff_t __desired) noexcept
     57 	: _M_sem(__desired)
     58       { }
     59 
     60       ~counting_semaphore() = default;
     61 
     62       counting_semaphore(const counting_semaphore&) = delete;
     63       counting_semaphore& operator=(const counting_semaphore&) = delete;
     64 
     65       static constexpr ptrdiff_t
     66       max() noexcept
     67       { return __least_max_value; }
     68 
     69       void
     70       release(ptrdiff_t __update = 1) noexcept(noexcept(_M_sem._M_release(1)))
     71       { _M_sem._M_release(__update); }
     72 
     73       void
     74       acquire() noexcept(noexcept(_M_sem._M_acquire()))
     75       { _M_sem._M_acquire(); }
     76 
     77       bool
     78       try_acquire() noexcept(noexcept(_M_sem._M_try_acquire()))
     79       { return _M_sem._M_try_acquire(); }
     80 
     81       template<typename _Rep, typename _Period>
     82 	bool
     83 	try_acquire_for(const std::chrono::duration<_Rep, _Period>& __rtime)
     84 	{ return _M_sem._M_try_acquire_for(__rtime); }
     85 
     86       template<typename _Clock, typename _Dur>
     87 	bool
     88 	try_acquire_until(const std::chrono::time_point<_Clock, _Dur>& __atime)
     89 	{ return _M_sem._M_try_acquire_until(__atime); }
     90     };
     91 
     92   using binary_semaphore = std::counting_semaphore<1>;
     93 
     94 _GLIBCXX_END_NAMESPACE_VERSION
     95 } // namespace
     96 #endif // cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
     97 #endif // __cpp_lib_semaphore
     98 #endif // _GLIBCXX_SEMAPHORE
     99