libstdc++
semaphore
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1// <semaphore> -*- C++ -*-
2
3// Copyright (C) 2020-2025 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#ifdef _GLIBCXX_SYSHDR
33#pragma GCC system_header
34#endif
35
36#include <bits/requires_hosted.h> // concurrency
37
38#if __cplusplus > 201703L
39#include <bits/semaphore_base.h>
40
41#define __glibcxx_want_semaphore
42#include <bits/version.h>
43
44#ifdef __cpp_lib_semaphore // C++ >= 20 && hosted && (atomic_wait || posix_sem)
45namespace std _GLIBCXX_VISIBILITY(default)
46{
47_GLIBCXX_BEGIN_NAMESPACE_VERSION
48
49 template<ptrdiff_t __least_max_value = __semaphore_impl::_S_max>
50 class counting_semaphore
51 {
52 static_assert(__least_max_value >= 0);
53 static_assert(__least_max_value <= __semaphore_impl::_S_max);
54
55 __semaphore_impl _M_sem;
56
57 public:
58 explicit counting_semaphore(ptrdiff_t __desired) noexcept
59 : _M_sem(__desired)
60 { }
61
62 ~counting_semaphore() = default;
63
64 counting_semaphore(const counting_semaphore&) = delete;
65 counting_semaphore& operator=(const counting_semaphore&) = delete;
66
67 static constexpr ptrdiff_t
68 max() noexcept
69 { return __least_max_value; }
70
71 void
72 release(ptrdiff_t __update = 1) noexcept(noexcept(_M_sem._M_release(1)))
73 { _M_sem._M_release(__update); }
74
75 void
76 acquire() noexcept(noexcept(_M_sem._M_acquire()))
77 { _M_sem._M_acquire(); }
78
79 bool
80 try_acquire() noexcept(noexcept(_M_sem._M_try_acquire()))
81 { return _M_sem._M_try_acquire(); }
82
83 template<typename _Rep, typename _Period>
84 bool
85 try_acquire_for(const std::chrono::duration<_Rep, _Period>& __rtime)
86 { return _M_sem._M_try_acquire_for(__rtime); }
87
88 template<typename _Clock, typename _Dur>
89 bool
90 try_acquire_until(const std::chrono::time_point<_Clock, _Dur>& __atime)
91 { return _M_sem._M_try_acquire_until(__atime); }
92 };
93
94 using binary_semaphore = std::counting_semaphore<1>;
95
96_GLIBCXX_END_NAMESPACE_VERSION
97} // namespace
98#endif // cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
99#endif // __cpp_lib_semaphore
100#endif // _GLIBCXX_SEMAPHORE
ISO C++ entities toplevel namespace is std.
chrono::duration represents a distance between two points in time
Definition chrono.h:516
chrono::time_point represents a point in time as measured by a clock
Definition chrono.h:927