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51 lines
1.2 KiB
C++
51 lines
1.2 KiB
C++
// Copyright 2018 Dolphin Emulator Project
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// SPDX-License-Identifier: GPL-2.0-or-later
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#pragma once
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#include <variant>
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namespace detail
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{
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template <typename... From>
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struct VariantCastProxy
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{
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const std::variant<From...>& v;
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template <typename... To>
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operator std::variant<To...>() const
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{
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return std::visit([](auto&& arg) { return std::variant<To...>{arg}; }, v);
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}
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};
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} // namespace detail
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template <typename... From>
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auto VariantCast(const std::variant<From...>& v)
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{
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return detail::VariantCastProxy<From...>{v};
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}
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template <class... Ts>
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struct overloaded : Ts...
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{
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using Ts::operator()...;
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};
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template <class... Ts>
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overloaded(Ts...) -> overloaded<Ts...>;
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// Visits a functor with a variant_alternative of the given index.
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// e.g. WithVariantAlternative<variant<int, float>>(1, func) calls func<float>()
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// An out-of-bounds index causes no visitation.
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template <typename Variant, std::size_t I = 0, typename Func>
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void WithVariantAlternative(std::size_t index, Func&& func)
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{
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if constexpr (I < std::variant_size_v<Variant>)
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{
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if (index == 0)
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func.template operator()<std::variant_alternative_t<I, Variant>>();
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else
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WithVariantAlternative<Variant, I + 1>(index - 1, std::forward<Func>(func));
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}
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}
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