1 // <semaphore> -*- C++ -*-
3 // Copyright (C) 2020-2025 Free Software Foundation, Inc.
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)
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.
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.
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/>.
25 /** @file include/semaphore
26 * This is a Standard C++ Library header.
29 #ifndef _GLIBCXX_SEMAPHORE
30 #define _GLIBCXX_SEMAPHORE 1
32 #ifdef _GLIBCXX_SYSHDR
33 #pragma GCC system_header
36 #include <bits/requires_hosted.h> // concurrency
38 #if __cplusplus > 201703L
39 #include <bits/semaphore_base.h>
41 #define __glibcxx_want_semaphore
42 #include <bits/version.h>
44 #ifdef __cpp_lib_semaphore // C++ >= 20 && hosted && (atomic_wait || posix_sem)
45 namespace std _GLIBCXX_VISIBILITY(default)
47 _GLIBCXX_BEGIN_NAMESPACE_VERSION
49 template<ptrdiff_t __least_max_value = __semaphore_impl::_S_max>
50 class counting_semaphore
52 static_assert(__least_max_value >= 0);
53 static_assert(__least_max_value <= __semaphore_impl::_S_max);
55 __semaphore_impl _M_sem;
58 explicit counting_semaphore(ptrdiff_t __desired) noexcept
62 ~counting_semaphore() = default;
64 counting_semaphore(const counting_semaphore&) = delete;
65 counting_semaphore& operator=(const counting_semaphore&) = delete;
67 static constexpr ptrdiff_t
69 { return __least_max_value; }
72 release(ptrdiff_t __update = 1) noexcept(noexcept(_M_sem._M_release(1)))
73 { _M_sem._M_release(__update); }
76 acquire() noexcept(noexcept(_M_sem._M_acquire()))
77 { _M_sem._M_acquire(); }
80 try_acquire() noexcept(noexcept(_M_sem._M_try_acquire()))
81 { return _M_sem._M_try_acquire(); }
83 template<typename _Rep, typename _Period>
85 try_acquire_for(const std::chrono::duration<_Rep, _Period>& __rtime)
86 { return _M_sem._M_try_acquire_for(__rtime); }
88 template<typename _Clock, typename _Dur>
90 try_acquire_until(const std::chrono::time_point<_Clock, _Dur>& __atime)
91 { return _M_sem._M_try_acquire_until(__atime); }
94 using binary_semaphore = std::counting_semaphore<1>;
96 _GLIBCXX_END_NAMESPACE_VERSION
98 #endif // cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
99 #endif // __cpp_lib_semaphore
100 #endif // _GLIBCXX_SEMAPHORE