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