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1 | // <latch> -*- C++ -*- |
2 | ||
99dee823 | 3 | // Copyright (C) 2020-2021 Free Software Foundation, Inc. |
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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/latch | |
26 | * This is a Standard C++ Library header. | |
27 | */ | |
28 | ||
29 | #ifndef _GLIBCXX_LATCH | |
71988274 | 30 | #define _GLIBCXX_LATCH 1 |
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31 | |
32 | #pragma GCC system_header | |
33 | ||
34 | #if __cplusplus > 201703L | |
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35 | |
36 | #include <bits/atomic_base.h> | |
37 | #include <ext/numeric_traits.h> | |
38 | ||
6591e422 | 39 | #if __cpp_lib_atomic_wait |
83a1beee TR |
40 | namespace std _GLIBCXX_VISIBILITY(default) |
41 | { | |
42 | _GLIBCXX_BEGIN_NAMESPACE_VERSION | |
43 | ||
71988274 JW |
44 | #define __cpp_lib_latch 201907L |
45 | ||
83a1beee TR |
46 | class latch |
47 | { | |
48 | public: | |
49 | static constexpr ptrdiff_t | |
50 | max() noexcept | |
51 | { return __gnu_cxx::__int_traits<ptrdiff_t>::__max; } | |
52 | ||
53 | constexpr explicit latch(ptrdiff_t __expected) noexcept | |
54 | : _M_a(__expected) { } | |
55 | ||
56 | ~latch() = default; | |
57 | latch(const latch&) = delete; | |
58 | latch& operator=(const latch&) = delete; | |
59 | ||
60 | _GLIBCXX_ALWAYS_INLINE void | |
61 | count_down(ptrdiff_t __update = 1) | |
62 | { | |
63 | auto const __old = __atomic_impl::fetch_sub(&_M_a, | |
64 | __update, memory_order::release); | |
65 | if (__old == __update) | |
66 | __atomic_impl::notify_all(&_M_a); | |
67 | } | |
68 | ||
69 | _GLIBCXX_ALWAYS_INLINE bool | |
70 | try_wait() const noexcept | |
71 | { return __atomic_impl::load(&_M_a, memory_order::acquire) == 0; } | |
72 | ||
73 | _GLIBCXX_ALWAYS_INLINE void | |
74 | wait() const noexcept | |
75 | { | |
76 | auto const __old = __atomic_impl::load(&_M_a, memory_order::acquire); | |
77 | std::__atomic_wait(&_M_a, __old, [this] { return this->try_wait(); }); | |
78 | } | |
79 | ||
80 | _GLIBCXX_ALWAYS_INLINE void | |
81 | arrive_and_wait(ptrdiff_t __update = 1) noexcept | |
82 | { | |
83 | count_down(__update); | |
84 | wait(); | |
85 | } | |
86 | ||
87 | private: | |
88 | alignas(__alignof__(ptrdiff_t)) ptrdiff_t _M_a; | |
89 | }; | |
90 | _GLIBCXX_END_NAMESPACE_VERSION | |
91 | } // namespace | |
6591e422 | 92 | #endif // __cpp_lib_atomic_wait |
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93 | #endif // __cplusplus > 201703L |
94 | #endif // _GLIBCXX_LATCH |