| 1 | #pragma once |
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| 2 | |
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| 3 | #include <mbgl/util/type_list.hpp> |
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| 4 | #include <mbgl/util/tuple.hpp> |
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| 5 | |
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| 6 | #include <type_traits> |
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| 7 | |
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| 8 | namespace mbgl { |
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| 9 | |
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| 10 | template <class T, class... Ts> |
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| 11 | struct TypeIndex; |
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| 12 | |
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| 13 | template <class T, class... Ts> |
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| 14 | struct TypeIndex<T, T, Ts...> : std::integral_constant<std::size_t, 0> {}; |
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| 15 | |
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| 16 | template <class T, class U, class... Ts> |
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| 17 | struct TypeIndex<T, U, Ts...> : std::integral_constant<std::size_t, 1 + TypeIndex<T, Ts...>::value> {}; |
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| 18 | |
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| 19 | template <class...> class IndexedTuple; |
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| 20 | |
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| 21 | // A tuple of Ts, where individual members can be accessed via `t.get<I>()` for I ∈ Is. |
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| 22 | // |
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| 23 | // See https://github.com/mapbox/cpp/blob/master/C%2B%2B%20Structural%20Metaprogramming.md |
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| 24 | // for motivation. |
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| 25 | // |
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| 26 | template <class... Is, class... Ts> |
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| 27 | class IndexedTuple<TypeList<Is...>, TypeList<Ts...>> : public tuple_polyfill<Ts...> { |
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| 28 | public: |
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| 29 | static_assert(sizeof...(Is) == sizeof...(Ts), "IndexedTuple size mismatch" ); |
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| 30 | |
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| 31 | using tuple_polyfill<Ts...>::tuple; |
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| 32 | |
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| 33 | template <class I> |
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| 34 | auto& get() { |
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| 35 | return get_polyfill<TypeIndex<I, Is...>::value>(*this); |
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| 36 | } |
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| 37 | |
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| 38 | template <class I> |
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| 39 | const auto& get() const { |
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| 40 | return get_polyfill<TypeIndex<I, Is...>::value>(*this); |
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| 41 | } |
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| 42 | |
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| 43 | template <class... Js, class... Us> |
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| 44 | IndexedTuple<TypeList<Is..., Js...>, TypeList<Ts..., Us...>> |
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| 45 | concat(const IndexedTuple<TypeList<Js...>, TypeList<Us...>>& other) const { |
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| 46 | return IndexedTuple<TypeList<Is..., Js...>, TypeList<Ts..., Us...>> { |
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| 47 | get<Is>()..., |
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| 48 | other.template get<Js>()... |
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| 49 | }; |
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| 50 | } |
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| 51 | }; |
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| 52 | |
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| 53 | } // namespace mbgl |
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| 54 | |
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