libstdc++
semaphore
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1 // <semaphore> -*- C++ -*-
2 
3 // Copyright (C) 2020-2021 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/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 #if __cplusplus > 201703L
35 #include <bits/semaphore_base.h>
36 #if __cpp_lib_atomic_wait
37 #include <ext/numeric_traits.h>
38 
39 namespace std _GLIBCXX_VISIBILITY(default)
40 {
41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
42 
43 #define __cpp_lib_semaphore 201907L
44 
45  template<ptrdiff_t __least_max_value =
46  __gnu_cxx::__int_traits<ptrdiff_t>::__max>
47  class counting_semaphore
48  {
49  static_assert(__least_max_value >= 0);
50 
51  __semaphore_impl<__least_max_value> _M_sem;
52 
53  public:
54  explicit counting_semaphore(ptrdiff_t __desired) noexcept
55  : _M_sem(__desired)
56  { }
57 
58  ~counting_semaphore() = default;
59 
60  counting_semaphore(const counting_semaphore&) = delete;
61  counting_semaphore& operator=(const counting_semaphore&) = delete;
62 
63  static constexpr ptrdiff_t
64  max() noexcept
65  { return __least_max_value; }
66 
67  void
68  release(ptrdiff_t __update = 1) noexcept(noexcept(_M_sem._M_release(1)))
69  { _M_sem._M_release(__update); }
70 
71  void
72  acquire() noexcept(noexcept(_M_sem._M_acquire()))
73  { _M_sem._M_acquire(); }
74 
75  bool
76  try_acquire() noexcept(noexcept(_M_sem._M_try_acquire()))
77  { return _M_sem._M_try_acquire(); }
78 
79  template<typename _Rep, typename _Period>
80  bool
81  try_acquire_for(const std::chrono::duration<_Rep, _Period>& __rtime)
82  { return _M_sem._M_try_acquire_for(__rtime); }
83 
84  template<typename _Clock, typename _Dur>
85  bool
86  try_acquire_until(const std::chrono::time_point<_Clock, _Dur>& __atime)
87  { return _M_sem._M_try_acquire_until(__atime); }
88  };
89 
90  using binary_semaphore = std::counting_semaphore<1>;
91 
92 _GLIBCXX_END_NAMESPACE_VERSION
93 } // namespace
94 #endif // __cpp_lib_atomic_wait
95 #endif // C++20
96 #endif // _GLIBCXX_SEMAPHORE