Merge pull request #411 from Razakhel/array_structured_binding

Added structured binding support for eastl::array
electronicarts · Feb 9, 2022 · ca6b871 · ca6b871
2 parents d1c2a9c + 8d5eb9e
commit ca6b871
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diff --git a/include/EASTL/array.h b/include/EASTL/array.h
@@ -478,9 +478,96 @@ namespace eastl
 		return internal::to_array(eastl::move(a), eastl::make_index_sequence<N>{});
 	}
 
+#if EASTL_TUPLE_ENABLED
+
+	template <typename T, size_t N>
+	class tuple_size<array<T, N>> : public integral_constant<size_t, N>
+	{
+	};
+
+	template <typename T, size_t N>
+	class tuple_size<const array<T, N>> : public integral_constant<size_t, N>
+	{
+	};
+
+	template <size_t I, typename T, size_t N>
+	class tuple_element<I, array<T, N>>
+	{
+	public:
+		using type = T;
+	};
+
+	template <size_t I, typename T, size_t N>
+	class tuple_element<I, const array<T, N>>
+	{
+	public:
+		using type = const T;
+	};
+
+	template <size_t I>
+	struct GetArray
+	{
+		template <typename T, size_t N>
+		static EA_CONSTEXPR T& getInternal(array<T, N>& a)
+		{
+			return a[I];
+		}
+
+		template <typename T, size_t N>
+		static EA_CONSTEXPR const T& getInternal(const array<T, N>& a)
+		{
+			return a[I];
+		}
+
+		template <typename T, size_t N>
+		static EA_CONSTEXPR T&& getInternal(array<T, N>&& a)
+		{
+			return eastl::forward<T>(a[I]);
+		}
+	};
+
+	template <size_t I, typename T, size_t N>
+	EA_CONSTEXPR tuple_element_t<I, array<T, N>>& get(array<T, N>& p)
+	{
+		return GetArray<I>::getInternal(p);
+	}
+
+	template <size_t I, typename T, size_t N>
+	EA_CONSTEXPR const tuple_element_t<I, array<T, N>>& get(const array<T, N>& p)
+	{
+		return GetArray<I>::getInternal(p);
+	}
+
+	template <size_t I, typename T, size_t N>
+	EA_CONSTEXPR tuple_element_t<I, array<T, N>>&& get(array<T, N>&& p)
+	{
+		return GetArray<I>::getInternal(eastl::move(p));
+	}
+
+#endif  // EASTL_TUPLE_ENABLED
+
 
 } // namespace eastl
 
+///////////////////////////////////////////////////////////////
+// C++17 structured binding support for eastl::array
+//
+#ifndef EA_COMPILER_NO_STRUCTURED_BINDING
+	#include <tuple>
+
+	template <typename T, size_t N>
+	class std::tuple_size<::eastl::array<T, N>> : public ::eastl::integral_constant<size_t, N>
+	{
+	};
+
+	template <size_t I, typename T, size_t N>
+	struct std::tuple_element<I, ::eastl::array<T, N>>
+	{
+		static_assert(I < N, "index is out of bounds");
+		using type = T;
+	};
+#endif // EA_COMPILER_NO_STRUCTURED_BINDING
+
 
 #endif // Header include guard
 

diff --git a/test/source/TestArray.cpp b/test/source/TestArray.cpp
@@ -132,6 +132,37 @@ int TestArray()
 			static_assert(eastl::is_same_v<decltype(deduced)::value_type, int>, "deduced array value_type mismatch");
 			VERIFY(deduced.size() == 5);
 		#endif
+
+		// structured binding
+
+		{
+			eastl::array<int, 5> aCopy = a;
+			auto&& [a0, a1, a2, a3, a4] = aCopy;
+
+			VERIFY(a0 == aCopy[0]);
+			VERIFY(a1 == aCopy[1]);
+			VERIFY(a2 == aCopy[2]);
+			VERIFY(a3 == aCopy[3]);
+			VERIFY(a4 == aCopy[4]);
+
+			a0 = 100;
+			VERIFY(aCopy[0] == 100);
+
+			a4 = 0;
+			VERIFY(aCopy[4] == 0);
+
+			// The deduced type may or may not be a reference type; it is an aliased type,
+			//  as per https://en.cppreference.com/w/cpp/language/structured_binding:
+			//  > Like a reference, a structured binding is an alias to an existing object. Unlike a reference,
+			//    the type of a structured binding does not have to be a reference type.
+			// Any reference specifier is thus removed to check only the type & its const qualifier
+			static_assert(eastl::is_same_v<eastl::remove_reference_t<decltype(a0)>, int>);
+
+			const eastl::array<int, 5> aConstCopy = a;
+			auto&& [aConst0, aConst1, aConst2, aConst3, aConst4] = aConstCopy;
+
+			static_assert(eastl::is_same_v<eastl::remove_reference_t<decltype(aConst0)>, const int>);
+		}
 	}
 
 	// constexpr tests