mirror of
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358 lines
11 KiB
C++
358 lines
11 KiB
C++
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/*
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/~` _ _ _|_. _ _ |_ | _
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\_,(_)| | | || ||_|(_||_)|(/_
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https://github.com/Naios/continuable
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v3.0.0
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Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files(the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions :
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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**/
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#ifndef CONTINUABLE_DETAIL_FLAT_VARIANT_HPP_INCLUDED
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#define CONTINUABLE_DETAIL_FLAT_VARIANT_HPP_INCLUDED
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#include <cassert>
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#include <cstdint>
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#include <limits>
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#include <memory>
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#include <type_traits>
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#include <utility>
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#include <continuable/detail/traits.hpp>
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namespace cti {
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namespace detail {
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namespace container {
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namespace detail {
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// We don't want to pull the algorithm header in
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template <typename... T>
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constexpr std::size_t max_element_of(std::initializer_list<std::size_t> list) {
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std::size_t m = 0;
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for (auto current : list) {
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if (current > m) {
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m = current;
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}
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}
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return m;
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}
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template <typename... T>
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constexpr auto storage_of_impl() {
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constexpr auto size = max_element_of({sizeof(T)...});
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constexpr auto align = max_element_of({alignof(T)...});
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return std::aligned_storage_t<size, align>{};
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}
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/// Declares the aligned storage union for the given types
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template <typename... T>
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using storage_of_t = decltype(storage_of_impl<T...>());
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/// The value fpr the empty slot
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using slot_t = std::uint8_t;
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/// The value which is used to mark the empty slot
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using empty_slot =
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std::integral_constant<slot_t, std::numeric_limits<slot_t>::max()>;
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template <typename... T>
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struct flat_variant_base {
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storage_of_t<T...> storage_;
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slot_t slot_;
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constexpr flat_variant_base() : slot_(empty_slot::value) {
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}
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flat_variant_base(flat_variant_base const&) noexcept {
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}
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flat_variant_base(flat_variant_base&&) noexcept {
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}
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flat_variant_base& operator=(flat_variant_base const&) {
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return *this;
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}
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flat_variant_base& operator=(flat_variant_base&&) {
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return *this;
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}
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};
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template <typename Base>
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struct flat_variant_move_base {
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constexpr flat_variant_move_base() = default;
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flat_variant_move_base(flat_variant_move_base const&) = default;
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explicit flat_variant_move_base(flat_variant_move_base&& right) {
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Base& me = *static_cast<Base*>(this);
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Base& other = *static_cast<Base*>(&right);
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if (other.is_empty()) {
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me.set_slot(empty_slot::value);
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} else {
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other.visit([&](auto&& value) {
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#ifndef NDEBUG
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me.set_slot(empty_slot::value);
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#endif
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// NOLINTNEXTLINE(misc-move-forwarding-reference)
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me.init(std::move(value), other.get_slot());
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});
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}
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other.destroy();
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}
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flat_variant_move_base& operator=(flat_variant_move_base const&) = default;
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flat_variant_move_base& operator=(flat_variant_move_base&& right) {
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Base& me = *static_cast<Base*>(this);
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Base& other = *static_cast<Base*>(&right);
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me.weak_destroy();
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if (other.is_empty()) {
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me.set_slot(empty_slot::value);
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} else {
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other.visit([&](auto&& value) {
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// ...
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me.init(std::move(value), other.get_slot());
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});
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}
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other.destroy();
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return *this;
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}
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};
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template <typename Base, bool IsCopyable /*= true*/>
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struct flat_variant_copy_base : flat_variant_move_base<Base> {
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constexpr flat_variant_copy_base() = default;
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flat_variant_copy_base(flat_variant_copy_base&&) = default;
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explicit flat_variant_copy_base(flat_variant_copy_base const& right)
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: flat_variant_move_base<Base>()
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// TODO noexcept(Base::is_nothrow_move_constructible)
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{
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Base& me = *static_cast<Base*>(this);
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Base const& other = *static_cast<Base const*>(&right);
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if (other.is_empty()) {
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me.set_slot(empty_slot::value);
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} else {
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other.visit([&](auto&& value) {
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#ifndef NDEBUG
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me.set_slot(empty_slot::value);
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#endif
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me.init(std::move(value), other.get_slot());
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});
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}
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}
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flat_variant_copy_base& operator=(flat_variant_copy_base&&) = default;
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flat_variant_copy_base& operator=(flat_variant_copy_base const& right)
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// TODO noexcept(Base::is_nothrow_move_constructible)
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{
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Base& me = *static_cast<Base*>(this);
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Base const& other = *static_cast<Base const*>(&right);
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me.weak_destroy();
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if (other.is_empty()) {
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me.set_slot(empty_slot::value);
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} else {
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other.visit([&](auto&& value) {
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// ...
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me.init(std::move(value), other.get_slot());
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});
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}
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return *this;
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}
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};
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template <typename Base /*, bool IsCopyable = false*/>
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struct flat_variant_copy_base<Base, false> : flat_variant_move_base<Base> {
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constexpr flat_variant_copy_base() = default;
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flat_variant_copy_base(flat_variant_copy_base const&) = delete;
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explicit flat_variant_copy_base(flat_variant_copy_base&& right) = default;
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flat_variant_copy_base& operator=(flat_variant_copy_base const&) = delete;
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flat_variant_copy_base& operator=(flat_variant_copy_base&&) = default;
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};
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/// Deduces to a true_type if all parameters T satisfy the predicate.
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template <template <typename> class Predicate, typename... T>
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using every = traits::conjunction<Predicate<T>...>;
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} // namespace detail
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/// A class similar to the one in the variant proposal,
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/// however it is capable of carrying an empty state by default.
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template <typename... T>
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class flat_variant;
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template <typename T>
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struct is_flat_variant : std::false_type {};
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template <typename... T>
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struct is_flat_variant<flat_variant<T...>> : std::true_type {};
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template <typename... T>
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class flat_variant
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: detail::flat_variant_copy_base<
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flat_variant<T...>,
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detail::every<std::is_copy_constructible, T...>::value>,
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detail::flat_variant_base<T...> {
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static_assert(sizeof...(T) > 0, "At least one paremeter T is required!");
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template <typename...>
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friend class flat_variant;
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template <typename>
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friend struct detail::flat_variant_move_base;
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template <typename, bool>
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friend struct detail::flat_variant_copy_base;
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template <typename V>
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flat_variant(V&& value, detail::slot_t const slot) {
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#ifndef NDEBUG
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set_slot(detail::empty_slot::value);
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#endif
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init(std::forward<V>(value), slot);
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}
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public:
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constexpr flat_variant() = default;
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flat_variant(flat_variant const&) = default;
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flat_variant(flat_variant&&) = default;
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flat_variant& operator=(flat_variant const&) = default;
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flat_variant& operator=(flat_variant&&) = default;
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~flat_variant() noexcept(
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detail::every<std::is_nothrow_destructible, T...>::value) {
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weak_destroy();
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}
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template <
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typename V,
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std::enable_if_t<!is_flat_variant<std::decay_t<V>>::value>* = nullptr>
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// Since the flat_variant isn't allowed through SFINAE
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// this overload is safed against the linted issue.
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// NOLINTNEXTLINE(misc-forwarding-reference-overload)
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explicit flat_variant(V&& value)
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: flat_variant(std::forward<V>(value),
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traits::index_of_t<std::decay_t<V>, T...>::value) {
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}
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template <
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typename V,
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std::enable_if_t<!is_flat_variant<std::decay_t<V>>::value>* = nullptr>
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flat_variant& operator=(V&& value) {
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weak_destroy();
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init(std::forward<V>(value),
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traits::index_of_t<std::decay_t<V>, T...>::value);
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return *this;
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}
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template <typename V, std::size_t Index =
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traits::index_of_t<std::decay_t<V>, T...>::value>
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bool is() const noexcept {
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return is_slot(Index);
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}
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bool is_empty() const noexcept {
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return is_slot(detail::empty_slot::value);
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}
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explicit constexpr operator bool() const noexcept {
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return !is_empty();
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}
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template <typename V>
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V& cast() noexcept {
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assert(is_slot(traits::index_of_t<std::decay_t<V>, T...>::value));
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return *reinterpret_cast<std::decay_t<V>*>(&this->storage_);
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}
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template <typename V>
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V const& cast() const noexcept {
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assert(is_slot(traits::index_of_t<std::decay_t<V>, T...>::value));
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return *reinterpret_cast<std::decay_t<V> const*>(&this->storage_);
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}
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private:
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template <typename C, typename V>
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static void visit_dispatch(flat_variant* me, V&& visitor) {
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std::forward<V>(visitor)(me->cast<C>());
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}
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template <typename C, typename V>
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static void visit_dispatch_const(flat_variant const* me, V&& visitor) {
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std::forward<V>(visitor)(me->cast<C>());
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}
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template <typename V>
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void visit(V&& visitor) {
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if (!is_empty()) {
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using callback_t = void (*)(flat_variant*, V &&);
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constexpr callback_t const callbacks[] = {&visit_dispatch<T, V>...};
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callbacks[get_slot()](this, std::forward<V>(visitor));
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}
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}
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template <typename V>
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void visit(V&& visitor) const {
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if (!is_empty()) {
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using callback_t = void (*)(flat_variant const*, V&&);
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constexpr callback_t const callbacks[] = {&visit_dispatch_const<T, V>...};
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callbacks[get_slot()](this, std::forward<V>(visitor));
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}
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}
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template <typename V>
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void init(V&& value, detail::slot_t const slot) {
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assert(is_empty());
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assert(sizeof(this->storage_) >= sizeof(std::decay_t<V>));
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using type = std::decay_t<V>;
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new (&this->storage_) type(std::forward<V>(value));
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set_slot(slot);
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}
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void destroy() {
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weak_destroy();
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#ifdef NDEBUG
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set_slot(detail::empty_slot::value);
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#endif
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}
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void weak_destroy() {
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visit([&](auto&& value) {
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using type = std::decay_t<decltype(value)>;
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value.~type();
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});
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#ifndef NDEBUG
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set_slot(detail::empty_slot::value);
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#endif
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}
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detail::slot_t get_slot() const noexcept {
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return this->slot_;
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}
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bool is_slot(detail::slot_t const slot) const noexcept {
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return get_slot() == slot;
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}
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void set_slot(detail::slot_t const slot) {
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this->slot_ = slot;
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}
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};
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} // namespace container
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} // namespace detail
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} // namespace cti
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#endif // CONTINUABLE_DETAIL_FLAT_VARIANT_HPP_INCLUDED
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