478 lines
14 KiB
C++
478 lines
14 KiB
C++
#pragma once
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/*
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* Copyright (C) 2024 Brett Terpstra
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#ifndef BLT_STD_VARIANT_H
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#define BLT_STD_VARIANT_H
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#include <functional>
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#include <optional>
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#include <tuple>
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#include <type_traits>
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#include <variant>
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#include <blt/std/types.h>
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namespace blt
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{
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template <typename... Types>
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class variant_t;
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namespace detail
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{
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template <typename... Ts>
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struct filter_void;
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template <>
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struct filter_void<>
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{
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using type = std::tuple<>;
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};
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template <typename T, typename... Ts>
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struct filter_void<T, Ts...>
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{
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using type = std::conditional_t<std::is_same_v<T, void>, typename filter_void<Ts...>::type, decltype(std::tuple_cat(
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std::declval<std::tuple<T>>(), std::declval<typename filter_void<Ts...>::type>()))>;
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};
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template <typename... Ts>
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using filter_void_t = typename filter_void<Ts...>::type;
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template <typename Type, typename... Ts>
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struct filter_invoke;
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template <typename Type>
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struct filter_invoke<Type>
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{
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using type = std::tuple<>;
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};
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template <typename Type, typename T, typename... Ts>
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struct filter_invoke<Type, T, Ts...>
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{
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using type = std::conditional_t<std::is_invocable_v<T, Type>, decltype(std::tuple_cat(
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std::declval<std::tuple<T>>(), std::declval<typename filter_invoke<Ts...>::type>())),
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typename filter_invoke<Ts...>::type>;
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};
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template <typename... Ts>
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using filter_invoke_t = typename filter_invoke<Ts...>::type;
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template <typename Type, typename Func>
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struct member_func_meta
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{
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using can_invoke = std::is_invocable<Func, Type>;
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using return_type = std::conditional_t<can_invoke::value, std::invoke_result_t<Func, Type>, void>;
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};
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template <typename T, typename Func, size_t Index>
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struct passthrough_value
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{
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using type = T;
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using func = Func;
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constexpr static size_t index = Index;
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bool has_value;
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explicit passthrough_value(const bool has_value): has_value(has_value)
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{}
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explicit operator bool() const
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{
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return has_value;
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}
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};
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template <typename Type, typename... Funcs>
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struct first_invoke_member_func
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{
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template <size_t... Indexes>
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constexpr static auto find_func(std::index_sequence<Indexes...>)
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{
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return (... || []() {
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using Meta = member_func_meta<Type, Funcs>;
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if constexpr (Meta::can_invoke::value)
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{
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return passthrough_value<typename Meta::return_type, Funcs, Indexes>{true};
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}
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return passthrough_value<typename Meta::return_type, Funcs, Indexes>{false};
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}());
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}
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using result = decltype(find_func(std::index_sequence_for<Funcs...>()));
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using return_type = typename result::type;
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using func_type = typename result::func;
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constexpr static size_t function_index = result::index;
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};
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template <typename FuncTuple, typename ArgTuple>
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struct member_func_detail;
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template <typename... Funcs, typename... Args>
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struct member_func_detail<std::tuple<Funcs...>, std::tuple<Args...>>
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{
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using result_types = std::tuple<first_invoke_member_func<Args, Funcs...>...>;
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using base_type = typename std::tuple_element_t<0, result_types>::return_type;
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template <typename T>
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using get_type = typename T::return_type;
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template <typename T>
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using is_base = std::is_same<T, base_type>;
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template <typename T>
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using is_base_or_void = std::disjunction<std::is_void<typename T::return_type>, is_base<typename T::return_type>>;
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template <template<typename...> typename Functor, template<typename> typename PerType, size_t... Indexes>
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constexpr static auto for_each_type(std::index_sequence<Indexes...>)
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{
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return std::declval<Functor<PerType<std::tuple_element_t<Indexes, result_types>>...>>;
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}
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constexpr static bool all_has_void = std::decay_t<std::invoke_result_t<decltype(for_each_type<std::conjunction, std::is_void>(
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std::index_sequence_for<Args...>()))>>::value;
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constexpr static bool all_has_ret = std::decay_t<std::invoke_result_t<decltype(for_each_type<std::conjunction, is_base>(
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std::index_sequence_for<Args...>()))>>::value;
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constexpr static bool all_has_ret_or_void = std::decay_t<std::invoke_result_t<decltype(for_each_type<std::conjunction, is_base_or_void>(
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std::index_sequence_for<Args...>()))>>::value;
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using non_void_types = typename std::decay_t<std::invoke_result_t<decltype(for_each_type<filter_void, get_type>(
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std::index_sequence_for<Args...>()))>>::type;
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template <size_t... Indexes>
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static constexpr auto make_variant(std::index_sequence<Indexes...>)
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{
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using variant = variant_t<std::decay_t<std::tuple_element_t<Indexes, non_void_types>>...>;
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return std::declval<variant>();
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}
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using make_return_type = std::conditional_t<all_has_void, void, std::conditional_t<
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all_has_ret, base_type, std::conditional_t<
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all_has_ret_or_void, std::optional<base_type>, std::conditional_t<
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std::tuple_size_v<non_void_types> == 0, void, decltype(make_variant(
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std::make_index_sequence<std::tuple_size_v<non_void_types>>{}))>>>>;
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};
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}
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/*
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* std::visit(blt::lambda_visitor{
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* lambdas...
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* }, data_variant);
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*/
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template <typename... TLambdas>
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struct lambda_visitor : TLambdas...
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{
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using TLambdas::operator()...;
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};
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#if __cplusplus < 202002L
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// explicit deduction guide (not needed as of C++20)
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template <typename... TLambdas>
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lambda_visitor(TLambdas...) -> lambda_visitor<TLambdas...>;
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#endif
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template <typename... Types>
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class variant_t
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{
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public:
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using value_type = std::variant<Types...>;
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size_t variant_size = sizeof...(Types);
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constexpr variant_t(): m_variant()
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{}
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constexpr variant_t(const variant_t& variant) noexcept(std::is_nothrow_copy_constructible_v<value_type>): m_variant(variant.m_variant)
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{}
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constexpr variant_t(variant_t&& variant) noexcept(std::is_nothrow_move_constructible_v<value_type>): m_variant(std::move(variant.m_variant))
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{}
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explicit constexpr variant_t(const value_type& variant) noexcept(std::is_nothrow_copy_constructible_v<value_type>): m_variant(variant)
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{}
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explicit constexpr variant_t(value_type&& variant) noexcept(std::is_nothrow_move_constructible_v<value_type>): m_variant(std::move(variant))
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{}
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explicit constexpr variant_t(Types&&... args) noexcept(std::is_nothrow_constructible_v<value_type, Types...>): m_variant(
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std::forward<Types>(args)...)
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{}
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template <typename T, typename... C_Args>
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explicit constexpr variant_t(std::in_place_type_t<T>, C_Args&&... args): m_variant(std::in_place_type<T>, std::forward<C_Args>(args)...)
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{}
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template <typename T, typename U, typename... C_Args>
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constexpr explicit variant_t(std::in_place_type_t<T>, std::initializer_list<U> il, C_Args&&... args): m_variant(
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std::in_place_type<T>, il, std::forward<C_Args>(args)...)
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{}
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template <size_t I, typename... C_Args>
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explicit constexpr variant_t(std::in_place_index_t<I>, C_Args&&... args): m_variant(std::in_place_index<I>, std::forward<C_Args>(args)...)
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{}
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template <std::size_t I, typename U, typename... C_Args>
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constexpr explicit variant_t(std::in_place_index_t<I>, std::initializer_list<U> il, C_Args&&... args): m_variant(
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std::in_place_index<I>, il, std::forward<C_Args>(args)...)
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{}
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template <typename T, typename... Args>
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T& emplace(Args&&... args)
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{
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return m_variant.template emplace<T>(std::forward<Args>(args)...);
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}
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template <typename T, typename U, typename... Args>
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T& emplace(std::initializer_list<U> il, Args&&... args)
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{
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return m_variant.template emplace<T>(il, std::forward<Args>(args)...);
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}
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template <std::size_t I, typename... Args>
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std::variant_alternative_t<I, value_type>& emplace(Args&&... args)
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{
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return m_variant.template emplace<I>(std::forward<Args>(args)...);
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}
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template <std::size_t I, typename U, typename... Args>
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std::variant_alternative_t<I, value_type>& emplace(std::initializer_list<U> il, Args&&... args)
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{
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return m_variant.template emplace<I>(il, std::forward<Args>(args)...);
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}
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[[nodiscard]] constexpr std::size_t index() const noexcept
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{
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return m_variant.index();
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}
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[[nodiscard]] constexpr bool valueless_by_exception() const noexcept
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{
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return m_variant.valueless_by_exception();
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}
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template <typename T>
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constexpr auto visit(T&& visitor) -> decltype(auto)
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{
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return std::visit(std::forward<T>(visitor), m_variant);
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}
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/**
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* Automatic visitor generation
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* @param visitees user lambdas
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*/
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template <typename... Visitee>
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constexpr auto visit(
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Visitee&&... visitees) -> typename detail::member_func_detail<std::tuple<Visitee...>, std::tuple<Types...>>::make_return_type
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{
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return std::visit(lambda_visitor{std::forward<Visitee>(visitees)...}, m_variant);
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}
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template <typename Default, typename... Visitee>
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constexpr auto visit_value(Default&& default_value, Visitee&&... visitees) -> decltype(auto)
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{
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return std::visit(lambda_visitor{
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std::forward<Visitee>(visitees)...,
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[default_value=std::forward<Default>(default_value)](auto&& value) {
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return std::forward<decltype(value)>(value);
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}
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});
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}
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template <typename MemberFunc, typename... Args>
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constexpr auto call_member(const MemberFunc func,
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Args&&... args) -> typename detail::member_func_detail<
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std::tuple<MemberFunc>, std::tuple<Types...>>::make_return_type
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{
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return std::visit([func,...args=std::forward<Args>(args)](auto&& value) {
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return ((value).*(func))(std::forward<Args>(args)...);
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}, m_variant);
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}
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template <size_t I>
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[[nodiscard]] constexpr bool has_index() const noexcept
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{
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return m_variant.index() == I;
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}
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template <typename T>
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[[nodiscard]] constexpr bool has_type() const noexcept
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{
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return std::holds_alternative<T>(m_variant);
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}
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template <typename T>
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[[nodiscard]] constexpr auto get() -> decltype(auto)
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{
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return std::get<T>(m_variant);
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}
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template <typename T>
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[[nodiscard]] constexpr auto get() const -> decltype(auto)
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{
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return std::get<T>(m_variant);
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}
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template <size_t I>
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[[nodiscard]] constexpr auto get() -> decltype(auto)
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{
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return std::get<I>(m_variant);
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}
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template <size_t I>
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[[nodiscard]] constexpr auto get() const -> decltype(auto)
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{
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return std::get<I>(m_variant);
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}
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template <size_t I>
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constexpr std::add_pointer_t<std::variant_alternative_t<I, value_type>> get_if() noexcept
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{
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return std::get_if<I>(m_variant);
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}
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template <size_t I>
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constexpr std::add_pointer_t<const std::variant_alternative_t<I, value_type>> get_if() noexcept
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{
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return std::get_if<I>(m_variant);
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}
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template <typename T>
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constexpr std::add_pointer_t<T> get_if() noexcept
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{
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return std::get_if<T>(m_variant);
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}
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template <typename T>
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constexpr std::add_pointer_t<const T> get_if() noexcept
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{
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return std::get_if<T>(m_variant);
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}
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template <typename T>
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constexpr T value_or(T&& t) const
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{
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if (has_type<T>())
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return get<T>();
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return std::forward<T>(t);
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}
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template <size_t I>
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constexpr std::variant_alternative_t<I, value_type> value_or(const std::variant_alternative_t<I, value_type>& t) const
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{
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if (has_type<std::variant_alternative_t<I, value_type>>())
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return get<I>();
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return t;
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}
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template <size_t I>
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constexpr std::variant_alternative_t<I, value_type> value_or(std::variant_alternative_t<I, value_type>&& t) const
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{
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if (has_type<std::variant_alternative_t<I, value_type>>())
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return get<I>();
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return t;
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}
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template <size_t>
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constexpr const value_type& variant() const
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{
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return m_variant;
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}
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constexpr value_type& variant()
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{
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return m_variant;
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}
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[[nodiscard]] constexpr size_t size() const
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{
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return variant_size;
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}
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friend bool operator==(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant == rhs.m_variant;
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}
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friend bool operator!=(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant != rhs.m_variant;
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}
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friend bool operator<(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant < rhs.m_variant;
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}
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friend bool operator>(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant > rhs.m_variant;
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}
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friend bool operator<=(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant <= rhs.m_variant;
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}
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friend bool operator>=(const variant_t& lhs, const variant_t& rhs)
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{
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return lhs.m_variant >= rhs.m_variant;
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}
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private:
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template <typename Derived, typename Base, typename ReturnType, typename... Args>
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static auto cast_member_ptr(ReturnType (Base::*base_func)(Args...))
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{
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return reinterpret_cast<ReturnType (Derived::*)(Args...)>(base_func);
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}
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value_type m_variant;
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};
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namespace detail
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{
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template <typename>
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class variant_is_base_of
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{};
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template <typename... Types>
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class variant_is_base_of<variant_t<Types...>>
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{
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public:
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using value_type = bool;
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template <typename T>
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static constexpr bool value = std::conjunction_v<std::is_base_of<T, Types>...>;
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};
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template <typename... Types>
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class variant_is_base_of<std::variant<Types...>>
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{
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public:
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using value_type = bool;
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template <typename T>
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static constexpr bool value = std::conjunction_v<std::is_base_of<T, Types>...>;
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};
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template <typename T>
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static constexpr bool variant_is_base_of_v = variant_is_base_of<T>::value;
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}
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}
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#endif //BLT_STD_VARIANT_H
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