diff options
Diffstat (limited to 'src/mbgl/util/indexed_tuple.hpp')
-rw-r--r-- | src/mbgl/util/indexed_tuple.hpp | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/src/mbgl/util/indexed_tuple.hpp b/src/mbgl/util/indexed_tuple.hpp new file mode 100644 index 0000000000..110e7dce12 --- /dev/null +++ b/src/mbgl/util/indexed_tuple.hpp @@ -0,0 +1,47 @@ +#pragma once + +#include <type_traits> +#include <tuple> + +namespace mbgl { + +template <class T, class... Ts> +struct TypeIndex; + +template <class T, class... Ts> +struct TypeIndex<T, T, Ts...> : std::integral_constant<std::size_t, 0> {}; + +template <class T, class U, class... Ts> +struct TypeIndex<T, U, Ts...> : std::integral_constant<std::size_t, 1 + TypeIndex<T, Ts...>::value> {}; + +template <class...> class TypeList {}; + +template <class...> class IndexedTuple; + +// A tuple of Ts, where individual members can be accessed via `t.get<I>()` for I ∈ Is. +// +// See https://github.com/mapbox/cpp/blob/master/C%2B%2B%20Structural%20Metaprogramming.md +// for motivation. +// +template <class... Is, class... Ts> +class IndexedTuple<TypeList<Is...>, TypeList<Ts...>> : public std::tuple<Ts...> { +public: + static_assert(sizeof...(Is) == sizeof...(Ts), "IndexedTuple size mismatch"); + + using std::tuple<Ts...>::tuple; + + template <class I> + static constexpr std::size_t Index = TypeIndex<I, Is...>::value; + + template <class I> + auto& get() { + return std::get<Index<I>>(*this); + } + + template <class I> + const auto& get() const { + return std::get<Index<I>>(*this); + } +}; + +} // namespace mbgl |