| 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 |
