diff options
Diffstat (limited to 'absl/container/internal/compressed_tuple.h')
| -rw-r--r-- | absl/container/internal/compressed_tuple.h | 162 |
1 files changed, 125 insertions, 37 deletions
diff --git a/absl/container/internal/compressed_tuple.h b/absl/container/internal/compressed_tuple.h index 29fe7c12..fbace496 100644 --- a/absl/container/internal/compressed_tuple.h +++ b/absl/container/internal/compressed_tuple.h @@ -4,7 +4,7 @@ // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // -// http://www.apache.org/licenses/LICENSE-2.0 +// https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, @@ -27,27 +27,28 @@ // const T2& t2 = value.get<2>(); // ... // -// http://en.cppreference.com/w/cpp/language/ebo +// https://en.cppreference.com/w/cpp/language/ebo #ifndef ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_ #define ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_ +#include <initializer_list> #include <tuple> #include <type_traits> #include <utility> #include "absl/utility/utility.h" -#ifdef _MSC_VER +#if defined(_MSC_VER) && !defined(__NVCC__) // We need to mark these classes with this declspec to ensure that // CompressedTuple happens. #define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC __declspec(empty_bases) -#else // _MSC_VER +#else #define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC -#endif // _MSC_VER +#endif namespace absl { -inline namespace lts_2018_12_18 { +inline namespace lts_2019_08_08 { namespace container_internal { template <typename... Ts> @@ -76,57 +77,110 @@ constexpr bool IsFinal() { #endif } +// We can't use EBCO on other CompressedTuples because that would mean that we +// derive from multiple Storage<> instantiations with the same I parameter, +// and potentially from multiple identical Storage<> instantiations. So anytime +// we use type inheritance rather than encapsulation, we mark +// CompressedTupleImpl, to make this easy to detect. +struct uses_inheritance {}; + template <typename T> constexpr bool ShouldUseBase() { - return std::is_class<T>::value && std::is_empty<T>::value && !IsFinal<T>(); + return std::is_class<T>::value && std::is_empty<T>::value && !IsFinal<T>() && + !std::is_base_of<uses_inheritance, T>::value; } // The storage class provides two specializations: // - For empty classes, it stores T as a base class. // - For everything else, it stores T as a member. -template <typename D, size_t I, bool = ShouldUseBase<ElemT<D, I>>()> +template <typename T, size_t I, +#if defined(_MSC_VER) + bool UseBase = + ShouldUseBase<typename std::enable_if<true, T>::type>()> +#else + bool UseBase = ShouldUseBase<T>()> +#endif struct Storage { - using T = ElemT<D, I>; T value; constexpr Storage() = default; - explicit constexpr Storage(T&& v) : value(absl::forward<T>(v)) {} - constexpr const T& get() const { return value; } - T& get() { return value; } + template <typename V> + explicit constexpr Storage(absl::in_place_t, V&& v) + : value(absl::forward<V>(v)) {} + constexpr const T& get() const& { return value; } + T& get() & { return value; } + constexpr const T&& get() const&& { return absl::move(*this).value; } + T&& get() && { return std::move(*this).value; } }; -template <typename D, size_t I> -struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage<D, I, true> - : ElemT<D, I> { - using T = internal_compressed_tuple::ElemT<D, I>; +template <typename T, size_t I> +struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage<T, I, true> : T { constexpr Storage() = default; - explicit constexpr Storage(T&& v) : T(absl::forward<T>(v)) {} - constexpr const T& get() const { return *this; } - T& get() { return *this; } + + template <typename V> + explicit constexpr Storage(absl::in_place_t, V&& v) + : T(absl::forward<V>(v)) {} + + constexpr const T& get() const& { return *this; } + T& get() & { return *this; } + constexpr const T&& get() const&& { return absl::move(*this); } + T&& get() && { return std::move(*this); } }; -template <typename D, typename I> +template <typename D, typename I, bool ShouldAnyUseBase> struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl; -template <typename... Ts, size_t... I> -struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC - CompressedTupleImpl<CompressedTuple<Ts...>, absl::index_sequence<I...>> +template <typename... Ts, size_t... I, bool ShouldAnyUseBase> +struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl< + CompressedTuple<Ts...>, absl::index_sequence<I...>, ShouldAnyUseBase> // We use the dummy identity function through std::integral_constant to // convince MSVC of accepting and expanding I in that context. Without it // you would get: // error C3548: 'I': parameter pack cannot be used in this context - : Storage<CompressedTuple<Ts...>, - std::integral_constant<size_t, I>::value>... { + : uses_inheritance, + Storage<Ts, std::integral_constant<size_t, I>::value>... { constexpr CompressedTupleImpl() = default; - explicit constexpr CompressedTupleImpl(Ts&&... args) - : Storage<CompressedTuple<Ts...>, I>(absl::forward<Ts>(args))... {} + template <typename... Vs> + explicit constexpr CompressedTupleImpl(absl::in_place_t, Vs&&... args) + : Storage<Ts, I>(absl::in_place, absl::forward<Vs>(args))... {} + friend CompressedTuple<Ts...>; }; +template <typename... Ts, size_t... I> +struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl< + CompressedTuple<Ts...>, absl::index_sequence<I...>, false> + // We use the dummy identity function as above... + : Storage<Ts, std::integral_constant<size_t, I>::value, false>... { + constexpr CompressedTupleImpl() = default; + template <typename... Vs> + explicit constexpr CompressedTupleImpl(absl::in_place_t, Vs&&... args) + : Storage<Ts, I, false>(absl::in_place, absl::forward<Vs>(args))... {} + friend CompressedTuple<Ts...>; +}; + +std::false_type Or(std::initializer_list<std::false_type>); +std::true_type Or(std::initializer_list<bool>); + +// MSVC requires this to be done separately rather than within the declaration +// of CompressedTuple below. +template <typename... Ts> +constexpr bool ShouldAnyUseBase() { + return decltype( + Or({std::integral_constant<bool, ShouldUseBase<Ts>()>()...})){}; +} + +template <typename T, typename V> +using TupleMoveConstructible = typename std::conditional< + std::is_reference<T>::value, std::is_convertible<V, T>, + std::is_constructible<T, V&&>>::type; + } // namespace internal_compressed_tuple // Helper class to perform the Empty Base Class Optimization. // Ts can contain classes and non-classes, empty or not. For the ones that // are empty classes, we perform the CompressedTuple. If all types in Ts are -// empty classes, then CompressedTuple<Ts...> is itself an empty class. +// empty classes, then CompressedTuple<Ts...> is itself an empty class. (This +// does not apply when one or more of those empty classes is itself an empty +// CompressedTuple.) // // To access the members, use member .get<N>() function. // @@ -138,28 +192,62 @@ struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC // const T2& t2 = value.get<2>(); // ... // -// http://en.cppreference.com/w/cpp/language/ebo +// https://en.cppreference.com/w/cpp/language/ebo template <typename... Ts> class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple : private internal_compressed_tuple::CompressedTupleImpl< - CompressedTuple<Ts...>, absl::index_sequence_for<Ts...>> { + CompressedTuple<Ts...>, absl::index_sequence_for<Ts...>, + internal_compressed_tuple::ShouldAnyUseBase<Ts...>()> { private: template <int I> using ElemT = internal_compressed_tuple::ElemT<CompressedTuple, I>; + template <int I> + using StorageT = internal_compressed_tuple::Storage<ElemT<I>, I>; + public: + // There seems to be a bug in MSVC dealing in which using '=default' here will + // cause the compiler to ignore the body of other constructors. The work- + // around is to explicitly implement the default constructor. +#if defined(_MSC_VER) + constexpr CompressedTuple() : CompressedTuple::CompressedTupleImpl() {} +#else constexpr CompressedTuple() = default; - explicit constexpr CompressedTuple(Ts... base) - : CompressedTuple::CompressedTupleImpl(absl::forward<Ts>(base)...) {} +#endif + explicit constexpr CompressedTuple(const Ts&... base) + : CompressedTuple::CompressedTupleImpl(absl::in_place, base...) {} + + template <typename... Vs, + absl::enable_if_t< + absl::conjunction< + // Ensure we are not hiding default copy/move constructors. + absl::negation<std::is_same<void(CompressedTuple), + void(absl::decay_t<Vs>...)>>, + internal_compressed_tuple::TupleMoveConstructible< + Ts, Vs&&>...>::value, + bool> = true> + explicit constexpr CompressedTuple(Vs&&... base) + : CompressedTuple::CompressedTupleImpl(absl::in_place, + absl::forward<Vs>(base)...) {} + + template <int I> + ElemT<I>& get() & { + return internal_compressed_tuple::Storage<ElemT<I>, I>::get(); + } + + template <int I> + constexpr const ElemT<I>& get() const& { + return StorageT<I>::get(); + } template <int I> - ElemT<I>& get() { - return internal_compressed_tuple::Storage<CompressedTuple, I>::get(); + ElemT<I>&& get() && { + return std::move(*this).StorageT<I>::get(); } template <int I> - constexpr const ElemT<I>& get() const { - return internal_compressed_tuple::Storage<CompressedTuple, I>::get(); + constexpr const ElemT<I>&& get() const&& { + return absl::move(*this).StorageT<I>::get(); } }; @@ -169,7 +257,7 @@ template <> class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple<> {}; } // namespace container_internal -} // inline namespace lts_2018_12_18 +} // inline namespace lts_2019_08_08 } // namespace absl #undef ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC |