1 | // <latch> -*- 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/latch
|
---|
26 | * This is a Standard C++ Library header.
|
---|
27 | */
|
---|
28 |
|
---|
29 | #ifndef _GLIBCXX_LATCH
|
---|
30 | #define _GLIBCXX_LATCH 1
|
---|
31 |
|
---|
32 | #pragma GCC system_header
|
---|
33 |
|
---|
34 | #if __cplusplus > 201703L
|
---|
35 |
|
---|
36 | #include <bits/atomic_base.h>
|
---|
37 | #include <ext/numeric_traits.h>
|
---|
38 |
|
---|
39 | #if __cpp_lib_atomic_wait
|
---|
40 | namespace std _GLIBCXX_VISIBILITY(default)
|
---|
41 | {
|
---|
42 | _GLIBCXX_BEGIN_NAMESPACE_VERSION
|
---|
43 |
|
---|
44 | #define __cpp_lib_latch 201907L
|
---|
45 |
|
---|
46 | class latch
|
---|
47 | {
|
---|
48 | public:
|
---|
49 | static constexpr ptrdiff_t
|
---|
50 | max() noexcept
|
---|
51 | { return __gnu_cxx::__int_traits<__detail::__platform_wait_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 __pred = [this] { return this->try_wait(); };
|
---|
77 | std::__atomic_wait_address(&_M_a, __pred);
|
---|
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__(__detail::__platform_wait_t)) __detail::__platform_wait_t _M_a;
|
---|
89 | };
|
---|
90 | _GLIBCXX_END_NAMESPACE_VERSION
|
---|
91 | } // namespace
|
---|
92 | #endif // __cpp_lib_atomic_wait
|
---|
93 | #endif // __cplusplus > 201703L
|
---|
94 | #endif // _GLIBCXX_LATCH
|
---|