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Diffstat (limited to 'contrib/llvm-project/libcxx/include/latch')
-rw-r--r-- | contrib/llvm-project/libcxx/include/latch | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/contrib/llvm-project/libcxx/include/latch b/contrib/llvm-project/libcxx/include/latch new file mode 100644 index 000000000000..10ae5721fbec --- /dev/null +++ b/contrib/llvm-project/libcxx/include/latch @@ -0,0 +1,112 @@ +// -*- C++ -*- +//===--------------------------- latch -----------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#ifndef _LIBCPP_LATCH +#define _LIBCPP_LATCH + +/* + latch synopsis + +namespace std +{ + + class latch + { + public: + static constexpr ptrdiff_t max() noexcept; + + constexpr explicit latch(ptrdiff_t __expected); + ~latch(); + + latch(const latch&) = delete; + latch& operator=(const latch&) = delete; + + void count_down(ptrdiff_t __update = 1); + bool try_wait() const noexcept; + void wait() const; + void arrive_and_wait(ptrdiff_t __update = 1); + + private: + ptrdiff_t __counter; // exposition only + }; + +} + +*/ + +#include <__availability> +#include <__config> +#include <atomic> + +#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) +#pragma GCC system_header +#endif + +#ifdef _LIBCPP_HAS_NO_THREADS +# error <latch> is not supported on this single threaded system +#endif + +_LIBCPP_PUSH_MACROS +#include <__undef_macros> + +#if _LIBCPP_STD_VER >= 14 + +_LIBCPP_BEGIN_NAMESPACE_STD + +class latch +{ + __atomic_base<ptrdiff_t> __a; + +public: + static constexpr ptrdiff_t max() noexcept { + return numeric_limits<ptrdiff_t>::max(); + } + + inline _LIBCPP_INLINE_VISIBILITY + constexpr explicit latch(ptrdiff_t __expected) : __a(__expected) { } + + ~latch() = default; + latch(const latch&) = delete; + latch& operator=(const latch&) = delete; + + inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY + void count_down(ptrdiff_t __update = 1) + { + auto const __old = __a.fetch_sub(__update, memory_order_release); + if(__old == __update) + __a.notify_all(); + } + inline _LIBCPP_INLINE_VISIBILITY + bool try_wait() const noexcept + { + return 0 == __a.load(memory_order_acquire); + } + inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY + void wait() const + { + auto const __test_fn = [=]() -> bool { + return try_wait(); + }; + __cxx_atomic_wait(&__a.__a_, __test_fn); + } + inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY + void arrive_and_wait(ptrdiff_t __update = 1) + { + count_down(__update); + wait(); + } +}; + +_LIBCPP_END_NAMESPACE_STD + +#endif // _LIBCPP_STD_VER >= 14 + +_LIBCPP_POP_MACROS + +#endif //_LIBCPP_LATCH |