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author | robot-contrib <robot-contrib@yandex-team.com> | 2022-08-13 15:53:36 +0300 |
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committer | robot-contrib <robot-contrib@yandex-team.com> | 2022-08-13 15:53:36 +0300 |
commit | 63727ce4a70378db0021af1d58d675ed4100939a (patch) | |
tree | 43d7186c2a145870276b344f7d65c6a33ae5e2c6 /contrib/libs/cxxsupp/libcxx/include/__ranges/copyable_box.h | |
parent | 05c17382d5a2fcbb4b947f1a856e0ac62e02aeb7 (diff) | |
download | ydb-63727ce4a70378db0021af1d58d675ed4100939a.tar.gz |
Update contrib/restricted/nlohmann_json to 3.11.2
Diffstat (limited to 'contrib/libs/cxxsupp/libcxx/include/__ranges/copyable_box.h')
-rw-r--r-- | contrib/libs/cxxsupp/libcxx/include/__ranges/copyable_box.h | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/contrib/libs/cxxsupp/libcxx/include/__ranges/copyable_box.h b/contrib/libs/cxxsupp/libcxx/include/__ranges/copyable_box.h new file mode 100644 index 0000000000..e1c08a7ea1 --- /dev/null +++ b/contrib/libs/cxxsupp/libcxx/include/__ranges/copyable_box.h @@ -0,0 +1,178 @@ +// -*- C++ -*- +//===----------------------------------------------------------------------===// +// +// 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___RANGES_COPYABLE_BOX_H +#define _LIBCPP___RANGES_COPYABLE_BOX_H + +#include <__config> +#include <__memory/addressof.h> +#include <__memory/construct_at.h> +#include <__utility/move.h> +#include <concepts> +#include <optional> +#include <type_traits> + +#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) +# pragma GCC system_header +#endif + +_LIBCPP_BEGIN_NAMESPACE_STD + +#if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) + +// __copyable_box allows turning a type that is copy-constructible (but maybe not copy-assignable) into +// a type that is both copy-constructible and copy-assignable. It does that by introducing an empty state +// and basically doing destroy-then-copy-construct in the assignment operator. The empty state is necessary +// to handle the case where the copy construction fails after destroying the object. +// +// In some cases, we can completely avoid the use of an empty state; we provide a specialization of +// __copyable_box that does this, see below for the details. + +template<class _Tp> +concept __copy_constructible_object = copy_constructible<_Tp> && is_object_v<_Tp>; + +namespace ranges { + // Primary template - uses std::optional and introduces an empty state in case assignment fails. + template<__copy_constructible_object _Tp> + class __copyable_box { + _LIBCPP_NO_UNIQUE_ADDRESS optional<_Tp> __val_; + + public: + template<class ..._Args> + requires is_constructible_v<_Tp, _Args...> + _LIBCPP_HIDE_FROM_ABI + constexpr explicit __copyable_box(in_place_t, _Args&& ...__args) + noexcept(is_nothrow_constructible_v<_Tp, _Args...>) + : __val_(in_place, std::forward<_Args>(__args)...) + { } + + _LIBCPP_HIDE_FROM_ABI + constexpr __copyable_box() noexcept(is_nothrow_default_constructible_v<_Tp>) + requires default_initializable<_Tp> + : __val_(in_place) + { } + + _LIBCPP_HIDE_FROM_ABI __copyable_box(__copyable_box const&) = default; + _LIBCPP_HIDE_FROM_ABI __copyable_box(__copyable_box&&) = default; + + _LIBCPP_HIDE_FROM_ABI + constexpr __copyable_box& operator=(__copyable_box const& __other) + noexcept(is_nothrow_copy_constructible_v<_Tp>) + { + if (this != std::addressof(__other)) { + if (__other.__has_value()) __val_.emplace(*__other); + else __val_.reset(); + } + return *this; + } + + _LIBCPP_HIDE_FROM_ABI + __copyable_box& operator=(__copyable_box&&) requires movable<_Tp> = default; + + _LIBCPP_HIDE_FROM_ABI + constexpr __copyable_box& operator=(__copyable_box&& __other) + noexcept(is_nothrow_move_constructible_v<_Tp>) + { + if (this != std::addressof(__other)) { + if (__other.__has_value()) __val_.emplace(std::move(*__other)); + else __val_.reset(); + } + return *this; + } + + _LIBCPP_HIDE_FROM_ABI constexpr _Tp const& operator*() const noexcept { return *__val_; } + _LIBCPP_HIDE_FROM_ABI constexpr _Tp& operator*() noexcept { return *__val_; } + + _LIBCPP_HIDE_FROM_ABI constexpr const _Tp *operator->() const noexcept { return __val_.operator->(); } + _LIBCPP_HIDE_FROM_ABI constexpr _Tp *operator->() noexcept { return __val_.operator->(); } + + _LIBCPP_HIDE_FROM_ABI constexpr bool __has_value() const noexcept { return __val_.has_value(); } + }; + + // This partial specialization implements an optimization for when we know we don't need to store + // an empty state to represent failure to perform an assignment. For copy-assignment, this happens: + // + // 1. If the type is copyable (which includes copy-assignment), we can use the type's own assignment operator + // directly and avoid using std::optional. + // 2. If the type is not copyable, but it is nothrow-copy-constructible, then we can implement assignment as + // destroy-and-then-construct and we know it will never fail, so we don't need an empty state. + // + // The exact same reasoning can be applied for move-assignment, with copyable replaced by movable and + // nothrow-copy-constructible replaced by nothrow-move-constructible. This specialization is enabled + // whenever we can apply any of these optimizations for both the copy assignment and the move assignment + // operator. + template<class _Tp> + concept __doesnt_need_empty_state_for_copy = copyable<_Tp> || is_nothrow_copy_constructible_v<_Tp>; + + template<class _Tp> + concept __doesnt_need_empty_state_for_move = movable<_Tp> || is_nothrow_move_constructible_v<_Tp>; + + template<__copy_constructible_object _Tp> + requires __doesnt_need_empty_state_for_copy<_Tp> && __doesnt_need_empty_state_for_move<_Tp> + class __copyable_box<_Tp> { + _LIBCPP_NO_UNIQUE_ADDRESS _Tp __val_; + + public: + template<class ..._Args> + requires is_constructible_v<_Tp, _Args...> + _LIBCPP_HIDE_FROM_ABI + constexpr explicit __copyable_box(in_place_t, _Args&& ...__args) + noexcept(is_nothrow_constructible_v<_Tp, _Args...>) + : __val_(std::forward<_Args>(__args)...) + { } + + _LIBCPP_HIDE_FROM_ABI + constexpr __copyable_box() noexcept(is_nothrow_default_constructible_v<_Tp>) + requires default_initializable<_Tp> + : __val_() + { } + + _LIBCPP_HIDE_FROM_ABI __copyable_box(__copyable_box const&) = default; + _LIBCPP_HIDE_FROM_ABI __copyable_box(__copyable_box&&) = default; + + // Implementation of assignment operators in case we perform optimization (1) + _LIBCPP_HIDE_FROM_ABI __copyable_box& operator=(__copyable_box const&) requires copyable<_Tp> = default; + _LIBCPP_HIDE_FROM_ABI __copyable_box& operator=(__copyable_box&&) requires movable<_Tp> = default; + + // Implementation of assignment operators in case we perform optimization (2) + _LIBCPP_HIDE_FROM_ABI + constexpr __copyable_box& operator=(__copyable_box const& __other) noexcept { + static_assert(is_nothrow_copy_constructible_v<_Tp>); + if (this != std::addressof(__other)) { + std::destroy_at(std::addressof(__val_)); + std::construct_at(std::addressof(__val_), __other.__val_); + } + return *this; + } + + _LIBCPP_HIDE_FROM_ABI + constexpr __copyable_box& operator=(__copyable_box&& __other) noexcept { + static_assert(is_nothrow_move_constructible_v<_Tp>); + if (this != std::addressof(__other)) { + std::destroy_at(std::addressof(__val_)); + std::construct_at(std::addressof(__val_), std::move(__other.__val_)); + } + return *this; + } + + _LIBCPP_HIDE_FROM_ABI constexpr _Tp const& operator*() const noexcept { return __val_; } + _LIBCPP_HIDE_FROM_ABI constexpr _Tp& operator*() noexcept { return __val_; } + + _LIBCPP_HIDE_FROM_ABI constexpr const _Tp *operator->() const noexcept { return std::addressof(__val_); } + _LIBCPP_HIDE_FROM_ABI constexpr _Tp *operator->() noexcept { return std::addressof(__val_); } + + _LIBCPP_HIDE_FROM_ABI constexpr bool __has_value() const noexcept { return true; } + }; +} // namespace ranges + +#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) + +_LIBCPP_END_NAMESPACE_STD + +#endif // _LIBCPP___RANGES_COPYABLE_BOX_H |