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)
43namespace 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(update: 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