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Diffstat (limited to 'third_party/abseil_cpp/absl/types/internal/variant.h')
-rw-r--r-- | third_party/abseil_cpp/absl/types/internal/variant.h | 1646 |
1 files changed, 0 insertions, 1646 deletions
diff --git a/third_party/abseil_cpp/absl/types/internal/variant.h b/third_party/abseil_cpp/absl/types/internal/variant.h deleted file mode 100644 index 772008c74e6d..000000000000 --- a/third_party/abseil_cpp/absl/types/internal/variant.h +++ /dev/null @@ -1,1646 +0,0 @@ -// Copyright 2018 The Abseil Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// 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, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. -// -// Implementation details of absl/types/variant.h, pulled into a -// separate file to avoid cluttering the top of the API header with -// implementation details. - -#ifndef ABSL_TYPES_variant_internal_H_ -#define ABSL_TYPES_variant_internal_H_ - -#include <cassert> -#include <cstddef> -#include <cstdlib> -#include <memory> -#include <stdexcept> -#include <tuple> -#include <type_traits> - -#include "absl/base/config.h" -#include "absl/base/internal/identity.h" -#include "absl/base/internal/inline_variable.h" -#include "absl/base/internal/invoke.h" -#include "absl/base/macros.h" -#include "absl/base/optimization.h" -#include "absl/meta/type_traits.h" -#include "absl/types/bad_variant_access.h" -#include "absl/utility/utility.h" - -#if !defined(ABSL_USES_STD_VARIANT) - -namespace absl { -ABSL_NAMESPACE_BEGIN - -template <class... Types> -class variant; - -ABSL_INTERNAL_INLINE_CONSTEXPR(size_t, variant_npos, static_cast<size_t>(-1)); - -template <class T> -struct variant_size; - -template <std::size_t I, class T> -struct variant_alternative; - -namespace variant_internal { - -// NOTE: See specializations below for details. -template <std::size_t I, class T> -struct VariantAlternativeSfinae {}; - -// Requires: I < variant_size_v<T>. -// -// Value: The Ith type of Types... -template <std::size_t I, class T0, class... Tn> -struct VariantAlternativeSfinae<I, variant<T0, Tn...>> - : VariantAlternativeSfinae<I - 1, variant<Tn...>> {}; - -// Value: T0 -template <class T0, class... Ts> -struct VariantAlternativeSfinae<0, variant<T0, Ts...>> { - using type = T0; -}; - -template <std::size_t I, class T> -using VariantAlternativeSfinaeT = typename VariantAlternativeSfinae<I, T>::type; - -// NOTE: Requires T to be a reference type. -template <class T, class U> -struct GiveQualsTo; - -template <class T, class U> -struct GiveQualsTo<T&, U> { - using type = U&; -}; - -template <class T, class U> -struct GiveQualsTo<T&&, U> { - using type = U&&; -}; - -template <class T, class U> -struct GiveQualsTo<const T&, U> { - using type = const U&; -}; - -template <class T, class U> -struct GiveQualsTo<const T&&, U> { - using type = const U&&; -}; - -template <class T, class U> -struct GiveQualsTo<volatile T&, U> { - using type = volatile U&; -}; - -template <class T, class U> -struct GiveQualsTo<volatile T&&, U> { - using type = volatile U&&; -}; - -template <class T, class U> -struct GiveQualsTo<volatile const T&, U> { - using type = volatile const U&; -}; - -template <class T, class U> -struct GiveQualsTo<volatile const T&&, U> { - using type = volatile const U&&; -}; - -template <class T, class U> -using GiveQualsToT = typename GiveQualsTo<T, U>::type; - -// Convenience alias, since size_t integral_constant is used a lot in this file. -template <std::size_t I> -using SizeT = std::integral_constant<std::size_t, I>; - -using NPos = SizeT<variant_npos>; - -template <class Variant, class T, class = void> -struct IndexOfConstructedType {}; - -template <std::size_t I, class Variant> -struct VariantAccessResultImpl; - -template <std::size_t I, template <class...> class Variantemplate, class... T> -struct VariantAccessResultImpl<I, Variantemplate<T...>&> { - using type = typename absl::variant_alternative<I, variant<T...>>::type&; -}; - -template <std::size_t I, template <class...> class Variantemplate, class... T> -struct VariantAccessResultImpl<I, const Variantemplate<T...>&> { - using type = - const typename absl::variant_alternative<I, variant<T...>>::type&; -}; - -template <std::size_t I, template <class...> class Variantemplate, class... T> -struct VariantAccessResultImpl<I, Variantemplate<T...>&&> { - using type = typename absl::variant_alternative<I, variant<T...>>::type&&; -}; - -template <std::size_t I, template <class...> class Variantemplate, class... T> -struct VariantAccessResultImpl<I, const Variantemplate<T...>&&> { - using type = - const typename absl::variant_alternative<I, variant<T...>>::type&&; -}; - -template <std::size_t I, class Variant> -using VariantAccessResult = - typename VariantAccessResultImpl<I, Variant&&>::type; - -// NOTE: This is used instead of std::array to reduce instantiation overhead. -template <class T, std::size_t Size> -struct SimpleArray { - static_assert(Size != 0, ""); - T value[Size]; -}; - -template <class T> -struct AccessedType { - using type = T; -}; - -template <class T> -using AccessedTypeT = typename AccessedType<T>::type; - -template <class T, std::size_t Size> -struct AccessedType<SimpleArray<T, Size>> { - using type = AccessedTypeT<T>; -}; - -template <class T> -constexpr T AccessSimpleArray(const T& value) { - return value; -} - -template <class T, std::size_t Size, class... SizeT> -constexpr AccessedTypeT<T> AccessSimpleArray(const SimpleArray<T, Size>& table, - std::size_t head_index, - SizeT... tail_indices) { - return AccessSimpleArray(table.value[head_index], tail_indices...); -} - -// Note: Intentionally is an alias. -template <class T> -using AlwaysZero = SizeT<0>; - -template <class Op, class... Vs> -struct VisitIndicesResultImpl { - using type = absl::result_of_t<Op(AlwaysZero<Vs>...)>; -}; - -template <class Op, class... Vs> -using VisitIndicesResultT = typename VisitIndicesResultImpl<Op, Vs...>::type; - -template <class ReturnType, class FunctionObject, class EndIndices, - class BoundIndices> -struct MakeVisitationMatrix; - -template <class ReturnType, class FunctionObject, std::size_t... Indices> -constexpr ReturnType call_with_indices(FunctionObject&& function) { - static_assert( - std::is_same<ReturnType, decltype(std::declval<FunctionObject>()( - SizeT<Indices>()...))>::value, - "Not all visitation overloads have the same return type."); - return absl::forward<FunctionObject>(function)(SizeT<Indices>()...); -} - -template <class ReturnType, class FunctionObject, std::size_t... BoundIndices> -struct MakeVisitationMatrix<ReturnType, FunctionObject, index_sequence<>, - index_sequence<BoundIndices...>> { - using ResultType = ReturnType (*)(FunctionObject&&); - static constexpr ResultType Run() { - return &call_with_indices<ReturnType, FunctionObject, - (BoundIndices - 1)...>; - } -}; - -template <typename Is, std::size_t J> -struct AppendToIndexSequence; - -template <typename Is, std::size_t J> -using AppendToIndexSequenceT = typename AppendToIndexSequence<Is, J>::type; - -template <std::size_t... Is, std::size_t J> -struct AppendToIndexSequence<index_sequence<Is...>, J> { - using type = index_sequence<Is..., J>; -}; - -template <class ReturnType, class FunctionObject, class EndIndices, - class CurrIndices, class BoundIndices> -struct MakeVisitationMatrixImpl; - -template <class ReturnType, class FunctionObject, class EndIndices, - std::size_t... CurrIndices, class BoundIndices> -struct MakeVisitationMatrixImpl<ReturnType, FunctionObject, EndIndices, - index_sequence<CurrIndices...>, BoundIndices> { - using ResultType = SimpleArray< - typename MakeVisitationMatrix<ReturnType, FunctionObject, EndIndices, - index_sequence<>>::ResultType, - sizeof...(CurrIndices)>; - - static constexpr ResultType Run() { - return {{MakeVisitationMatrix< - ReturnType, FunctionObject, EndIndices, - AppendToIndexSequenceT<BoundIndices, CurrIndices>>::Run()...}}; - } -}; - -template <class ReturnType, class FunctionObject, std::size_t HeadEndIndex, - std::size_t... TailEndIndices, std::size_t... BoundIndices> -struct MakeVisitationMatrix<ReturnType, FunctionObject, - index_sequence<HeadEndIndex, TailEndIndices...>, - index_sequence<BoundIndices...>> - : MakeVisitationMatrixImpl<ReturnType, FunctionObject, - index_sequence<TailEndIndices...>, - absl::make_index_sequence<HeadEndIndex>, - index_sequence<BoundIndices...>> {}; - -struct UnreachableSwitchCase { - template <class Op> - [[noreturn]] static VisitIndicesResultT<Op, std::size_t> Run( - Op&& /*ignored*/) { -#if ABSL_HAVE_BUILTIN(__builtin_unreachable) || \ - (defined(__GNUC__) && !defined(__clang__)) - __builtin_unreachable(); -#elif defined(_MSC_VER) - __assume(false); -#else - // Try to use assert of false being identified as an unreachable intrinsic. - // NOTE: We use assert directly to increase chances of exploiting an assume - // intrinsic. - assert(false); // NOLINT - - // Hack to silence potential no return warning -- cause an infinite loop. - return Run(absl::forward<Op>(op)); -#endif // Checks for __builtin_unreachable - } -}; - -template <class Op, std::size_t I> -struct ReachableSwitchCase { - static VisitIndicesResultT<Op, std::size_t> Run(Op&& op) { - return absl::base_internal::invoke(absl::forward<Op>(op), SizeT<I>()); - } -}; - -// The number 33 is just a guess at a reasonable maximum to our switch. It is -// not based on any analysis. The reason it is a power of 2 plus 1 instead of a -// power of 2 is because the number was picked to correspond to a power of 2 -// amount of "normal" alternatives, plus one for the possibility of the user -// providing "monostate" in addition to the more natural alternatives. -ABSL_INTERNAL_INLINE_CONSTEXPR(std::size_t, MaxUnrolledVisitCases, 33); - -// Note: The default-definition is for unreachable cases. -template <bool IsReachable> -struct PickCaseImpl { - template <class Op, std::size_t I> - using Apply = UnreachableSwitchCase; -}; - -template <> -struct PickCaseImpl</*IsReachable =*/true> { - template <class Op, std::size_t I> - using Apply = ReachableSwitchCase<Op, I>; -}; - -// Note: This form of dance with template aliases is to make sure that we -// instantiate a number of templates proportional to the number of variant -// alternatives rather than a number of templates proportional to our -// maximum unrolled amount of visitation cases (aliases are effectively -// "free" whereas other template instantiations are costly). -template <class Op, std::size_t I, std::size_t EndIndex> -using PickCase = typename PickCaseImpl<(I < EndIndex)>::template Apply<Op, I>; - -template <class ReturnType> -[[noreturn]] ReturnType TypedThrowBadVariantAccess() { - absl::variant_internal::ThrowBadVariantAccess(); -} - -// Given N variant sizes, determine the number of cases there would need to be -// in a single switch-statement that would cover every possibility in the -// corresponding N-ary visit operation. -template <std::size_t... NumAlternatives> -struct NumCasesOfSwitch; - -template <std::size_t HeadNumAlternatives, std::size_t... TailNumAlternatives> -struct NumCasesOfSwitch<HeadNumAlternatives, TailNumAlternatives...> { - static constexpr std::size_t value = - (HeadNumAlternatives + 1) * - NumCasesOfSwitch<TailNumAlternatives...>::value; -}; - -template <> -struct NumCasesOfSwitch<> { - static constexpr std::size_t value = 1; -}; - -// A switch statement optimizes better than the table of function pointers. -template <std::size_t EndIndex> -struct VisitIndicesSwitch { - static_assert(EndIndex <= MaxUnrolledVisitCases, - "Maximum unrolled switch size exceeded."); - - template <class Op> - static VisitIndicesResultT<Op, std::size_t> Run(Op&& op, std::size_t i) { - switch (i) { - case 0: - return PickCase<Op, 0, EndIndex>::Run(absl::forward<Op>(op)); - case 1: - return PickCase<Op, 1, EndIndex>::Run(absl::forward<Op>(op)); - case 2: - return PickCase<Op, 2, EndIndex>::Run(absl::forward<Op>(op)); - case 3: - return PickCase<Op, 3, EndIndex>::Run(absl::forward<Op>(op)); - case 4: - return PickCase<Op, 4, EndIndex>::Run(absl::forward<Op>(op)); - case 5: - return PickCase<Op, 5, EndIndex>::Run(absl::forward<Op>(op)); - case 6: - return PickCase<Op, 6, EndIndex>::Run(absl::forward<Op>(op)); - case 7: - return PickCase<Op, 7, EndIndex>::Run(absl::forward<Op>(op)); - case 8: - return PickCase<Op, 8, EndIndex>::Run(absl::forward<Op>(op)); - case 9: - return PickCase<Op, 9, EndIndex>::Run(absl::forward<Op>(op)); - case 10: - return PickCase<Op, 10, EndIndex>::Run(absl::forward<Op>(op)); - case 11: - return PickCase<Op, 11, EndIndex>::Run(absl::forward<Op>(op)); - case 12: - return PickCase<Op, 12, EndIndex>::Run(absl::forward<Op>(op)); - case 13: - return PickCase<Op, 13, EndIndex>::Run(absl::forward<Op>(op)); - case 14: - return PickCase<Op, 14, EndIndex>::Run(absl::forward<Op>(op)); - case 15: - return PickCase<Op, 15, EndIndex>::Run(absl::forward<Op>(op)); - case 16: - return PickCase<Op, 16, EndIndex>::Run(absl::forward<Op>(op)); - case 17: - return PickCase<Op, 17, EndIndex>::Run(absl::forward<Op>(op)); - case 18: - return PickCase<Op, 18, EndIndex>::Run(absl::forward<Op>(op)); - case 19: - return PickCase<Op, 19, EndIndex>::Run(absl::forward<Op>(op)); - case 20: - return PickCase<Op, 20, EndIndex>::Run(absl::forward<Op>(op)); - case 21: - return PickCase<Op, 21, EndIndex>::Run(absl::forward<Op>(op)); - case 22: - return PickCase<Op, 22, EndIndex>::Run(absl::forward<Op>(op)); - case 23: - return PickCase<Op, 23, EndIndex>::Run(absl::forward<Op>(op)); - case 24: - return PickCase<Op, 24, EndIndex>::Run(absl::forward<Op>(op)); - case 25: - return PickCase<Op, 25, EndIndex>::Run(absl::forward<Op>(op)); - case 26: - return PickCase<Op, 26, EndIndex>::Run(absl::forward<Op>(op)); - case 27: - return PickCase<Op, 27, EndIndex>::Run(absl::forward<Op>(op)); - case 28: - return PickCase<Op, 28, EndIndex>::Run(absl::forward<Op>(op)); - case 29: - return PickCase<Op, 29, EndIndex>::Run(absl::forward<Op>(op)); - case 30: - return PickCase<Op, 30, EndIndex>::Run(absl::forward<Op>(op)); - case 31: - return PickCase<Op, 31, EndIndex>::Run(absl::forward<Op>(op)); - case 32: - return PickCase<Op, 32, EndIndex>::Run(absl::forward<Op>(op)); - default: - ABSL_ASSERT(i == variant_npos); - return absl::base_internal::invoke(absl::forward<Op>(op), NPos()); - } - } -}; - -template <std::size_t... EndIndices> -struct VisitIndicesFallback { - template <class Op, class... SizeT> - static VisitIndicesResultT<Op, SizeT...> Run(Op&& op, SizeT... indices) { - return AccessSimpleArray( - MakeVisitationMatrix<VisitIndicesResultT<Op, SizeT...>, Op, - index_sequence<(EndIndices + 1)...>, - index_sequence<>>::Run(), - (indices + 1)...)(absl::forward<Op>(op)); - } -}; - -// Take an N-dimensional series of indices and convert them into a single index -// without loss of information. The purpose of this is to be able to convert an -// N-ary visit operation into a single switch statement. -template <std::size_t...> -struct FlattenIndices; - -template <std::size_t HeadSize, std::size_t... TailSize> -struct FlattenIndices<HeadSize, TailSize...> { - template<class... SizeType> - static constexpr std::size_t Run(std::size_t head, SizeType... tail) { - return head + HeadSize * FlattenIndices<TailSize...>::Run(tail...); - } -}; - -template <> -struct FlattenIndices<> { - static constexpr std::size_t Run() { return 0; } -}; - -// Take a single "flattened" index (flattened by FlattenIndices) and determine -// the value of the index of one of the logically represented dimensions. -template <std::size_t I, std::size_t IndexToGet, std::size_t HeadSize, - std::size_t... TailSize> -struct UnflattenIndex { - static constexpr std::size_t value = - UnflattenIndex<I / HeadSize, IndexToGet - 1, TailSize...>::value; -}; - -template <std::size_t I, std::size_t HeadSize, std::size_t... TailSize> -struct UnflattenIndex<I, 0, HeadSize, TailSize...> { - static constexpr std::size_t value = (I % HeadSize); -}; - -// The backend for converting an N-ary visit operation into a unary visit. -template <class IndexSequence, std::size_t... EndIndices> -struct VisitIndicesVariadicImpl; - -template <std::size_t... N, std::size_t... EndIndices> -struct VisitIndicesVariadicImpl<absl::index_sequence<N...>, EndIndices...> { - // A type that can take an N-ary function object and converts it to a unary - // function object that takes a single, flattened index, and "unflattens" it - // into its individual dimensions when forwarding to the wrapped object. - template <class Op> - struct FlattenedOp { - template <std::size_t I> - VisitIndicesResultT<Op, decltype(EndIndices)...> operator()( - SizeT<I> /*index*/) && { - return base_internal::invoke( - absl::forward<Op>(op), - SizeT<UnflattenIndex<I, N, (EndIndices + 1)...>::value - - std::size_t{1}>()...); - } - - Op&& op; - }; - - template <class Op, class... SizeType> - static VisitIndicesResultT<Op, decltype(EndIndices)...> Run( - Op&& op, SizeType... i) { - return VisitIndicesSwitch<NumCasesOfSwitch<EndIndices...>::value>::Run( - FlattenedOp<Op>{absl::forward<Op>(op)}, - FlattenIndices<(EndIndices + std::size_t{1})...>::Run( - (i + std::size_t{1})...)); - } -}; - -template <std::size_t... EndIndices> -struct VisitIndicesVariadic - : VisitIndicesVariadicImpl<absl::make_index_sequence<sizeof...(EndIndices)>, - EndIndices...> {}; - -// This implementation will flatten N-ary visit operations into a single switch -// statement when the number of cases would be less than our maximum specified -// switch-statement size. -// TODO(calabrese) -// Based on benchmarks, determine whether the function table approach actually -// does optimize better than a chain of switch statements and possibly update -// the implementation accordingly. Also consider increasing the maximum switch -// size. -template <std::size_t... EndIndices> -struct VisitIndices - : absl::conditional_t<(NumCasesOfSwitch<EndIndices...>::value <= - MaxUnrolledVisitCases), - VisitIndicesVariadic<EndIndices...>, - VisitIndicesFallback<EndIndices...>> {}; - -template <std::size_t EndIndex> -struct VisitIndices<EndIndex> - : absl::conditional_t<(EndIndex <= MaxUnrolledVisitCases), - VisitIndicesSwitch<EndIndex>, - VisitIndicesFallback<EndIndex>> {}; - -// Suppress bogus warning on MSVC: MSVC complains that the `reinterpret_cast` -// below is returning the address of a temporary or local object. -#ifdef _MSC_VER -#pragma warning(push) -#pragma warning(disable : 4172) -#endif // _MSC_VER - -// TODO(calabrese) std::launder -// TODO(calabrese) constexpr -// NOTE: DO NOT REMOVE the `inline` keyword as it is necessary to work around a -// MSVC bug. See https://github.com/abseil/abseil-cpp/issues/129 for details. -template <class Self, std::size_t I> -inline VariantAccessResult<I, Self> AccessUnion(Self&& self, SizeT<I> /*i*/) { - return reinterpret_cast<VariantAccessResult<I, Self>>(self); -} - -#ifdef _MSC_VER -#pragma warning(pop) -#endif // _MSC_VER - -template <class T> -void DeducedDestroy(T& self) { // NOLINT - self.~T(); -} - -// NOTE: This type exists as a single entity for variant and its bases to -// befriend. It contains helper functionality that manipulates the state of the -// variant, such as the implementation of things like assignment and emplace -// operations. -struct VariantCoreAccess { - template <class VariantType> - static typename VariantType::Variant& Derived(VariantType& self) { // NOLINT - return static_cast<typename VariantType::Variant&>(self); - } - - template <class VariantType> - static const typename VariantType::Variant& Derived( - const VariantType& self) { // NOLINT - return static_cast<const typename VariantType::Variant&>(self); - } - - template <class VariantType> - static void Destroy(VariantType& self) { // NOLINT - Derived(self).destroy(); - self.index_ = absl::variant_npos; - } - - template <class Variant> - static void SetIndex(Variant& self, std::size_t i) { // NOLINT - self.index_ = i; - } - - template <class Variant> - static void InitFrom(Variant& self, Variant&& other) { // NOLINT - VisitIndices<absl::variant_size<Variant>::value>::Run( - InitFromVisitor<Variant, Variant&&>{&self, - std::forward<Variant>(other)}, - other.index()); - self.index_ = other.index(); - } - - // Access a variant alternative, assuming the index is correct. - template <std::size_t I, class Variant> - static VariantAccessResult<I, Variant> Access(Variant&& self) { - // This cast instead of invocation of AccessUnion with an rvalue is a - // workaround for msvc. Without this there is a runtime failure when dealing - // with rvalues. - // TODO(calabrese) Reduce test case and find a simpler workaround. - return static_cast<VariantAccessResult<I, Variant>>( - variant_internal::AccessUnion(self.state_, SizeT<I>())); - } - - // Access a variant alternative, throwing if the index is incorrect. - template <std::size_t I, class Variant> - static VariantAccessResult<I, Variant> CheckedAccess(Variant&& self) { - if (ABSL_PREDICT_FALSE(self.index_ != I)) { - TypedThrowBadVariantAccess<VariantAccessResult<I, Variant>>(); - } - - return Access<I>(absl::forward<Variant>(self)); - } - - // The implementation of the move-assignment operation for a variant. - template <class VType> - struct MoveAssignVisitor { - using DerivedType = typename VType::Variant; - template <std::size_t NewIndex> - void operator()(SizeT<NewIndex> /*new_i*/) const { - if (left->index_ == NewIndex) { - Access<NewIndex>(*left) = std::move(Access<NewIndex>(*right)); - } else { - Derived(*left).template emplace<NewIndex>( - std::move(Access<NewIndex>(*right))); - } - } - - void operator()(SizeT<absl::variant_npos> /*new_i*/) const { - Destroy(*left); - } - - VType* left; - VType* right; - }; - - template <class VType> - static MoveAssignVisitor<VType> MakeMoveAssignVisitor(VType* left, - VType* other) { - return {left, other}; - } - - // The implementation of the assignment operation for a variant. - template <class VType> - struct CopyAssignVisitor { - using DerivedType = typename VType::Variant; - template <std::size_t NewIndex> - void operator()(SizeT<NewIndex> /*new_i*/) const { - using New = - typename absl::variant_alternative<NewIndex, DerivedType>::type; - - if (left->index_ == NewIndex) { - Access<NewIndex>(*left) = Access<NewIndex>(*right); - } else if (std::is_nothrow_copy_constructible<New>::value || - !std::is_nothrow_move_constructible<New>::value) { - Derived(*left).template emplace<NewIndex>(Access<NewIndex>(*right)); - } else { - Derived(*left) = DerivedType(Derived(*right)); - } - } - - void operator()(SizeT<absl::variant_npos> /*new_i*/) const { - Destroy(*left); - } - - VType* left; - const VType* right; - }; - - template <class VType> - static CopyAssignVisitor<VType> MakeCopyAssignVisitor(VType* left, - const VType& other) { - return {left, &other}; - } - - // The implementation of conversion-assignment operations for variant. - template <class Left, class QualifiedNew> - struct ConversionAssignVisitor { - using NewIndex = - variant_internal::IndexOfConstructedType<Left, QualifiedNew>; - - void operator()(SizeT<NewIndex::value> /*old_i*/ - ) const { - Access<NewIndex::value>(*left) = absl::forward<QualifiedNew>(other); - } - - template <std::size_t OldIndex> - void operator()(SizeT<OldIndex> /*old_i*/ - ) const { - using New = - typename absl::variant_alternative<NewIndex::value, Left>::type; - if (std::is_nothrow_constructible<New, QualifiedNew>::value || - !std::is_nothrow_move_constructible<New>::value) { - left->template emplace<NewIndex::value>( - absl::forward<QualifiedNew>(other)); - } else { - // the standard says "equivalent to - // operator=(variant(std::forward<T>(t)))", but we use `emplace` here - // because the variant's move assignment operator could be deleted. - left->template emplace<NewIndex::value>( - New(absl::forward<QualifiedNew>(other))); - } - } - - Left* left; - QualifiedNew&& other; - }; - - template <class Left, class QualifiedNew> - static ConversionAssignVisitor<Left, QualifiedNew> - MakeConversionAssignVisitor(Left* left, QualifiedNew&& qual) { - return {left, absl::forward<QualifiedNew>(qual)}; - } - - // Backend for operations for `emplace()` which destructs `*self` then - // construct a new alternative with `Args...`. - template <std::size_t NewIndex, class Self, class... Args> - static typename absl::variant_alternative<NewIndex, Self>::type& Replace( - Self* self, Args&&... args) { - Destroy(*self); - using New = typename absl::variant_alternative<NewIndex, Self>::type; - New* const result = ::new (static_cast<void*>(&self->state_)) - New(absl::forward<Args>(args)...); - self->index_ = NewIndex; - return *result; - } - - template <class LeftVariant, class QualifiedRightVariant> - struct InitFromVisitor { - template <std::size_t NewIndex> - void operator()(SizeT<NewIndex> /*new_i*/) const { - using Alternative = - typename variant_alternative<NewIndex, LeftVariant>::type; - ::new (static_cast<void*>(&left->state_)) Alternative( - Access<NewIndex>(std::forward<QualifiedRightVariant>(right))); - } - - void operator()(SizeT<absl::variant_npos> /*new_i*/) const { - // This space intentionally left blank. - } - LeftVariant* left; - QualifiedRightVariant&& right; - }; -}; - -template <class Expected, class... T> -struct IndexOfImpl; - -template <class Expected> -struct IndexOfImpl<Expected> { - using IndexFromEnd = SizeT<0>; - using MatchedIndexFromEnd = IndexFromEnd; - using MultipleMatches = std::false_type; -}; - -template <class Expected, class Head, class... Tail> -struct IndexOfImpl<Expected, Head, Tail...> : IndexOfImpl<Expected, Tail...> { - using IndexFromEnd = - SizeT<IndexOfImpl<Expected, Tail...>::IndexFromEnd::value + 1>; -}; - -template <class Expected, class... Tail> -struct IndexOfImpl<Expected, Expected, Tail...> - : IndexOfImpl<Expected, Tail...> { - using IndexFromEnd = - SizeT<IndexOfImpl<Expected, Tail...>::IndexFromEnd::value + 1>; - using MatchedIndexFromEnd = IndexFromEnd; - using MultipleMatches = std::integral_constant< - bool, IndexOfImpl<Expected, Tail...>::MatchedIndexFromEnd::value != 0>; -}; - -template <class Expected, class... Types> -struct IndexOfMeta { - using Results = IndexOfImpl<Expected, Types...>; - static_assert(!Results::MultipleMatches::value, - "Attempted to access a variant by specifying a type that " - "matches more than one alternative."); - static_assert(Results::MatchedIndexFromEnd::value != 0, - "Attempted to access a variant by specifying a type that does " - "not match any alternative."); - using type = SizeT<sizeof...(Types) - Results::MatchedIndexFromEnd::value>; -}; - -template <class Expected, class... Types> -using IndexOf = typename IndexOfMeta<Expected, Types...>::type; - -template <class Variant, class T, std::size_t CurrIndex> -struct UnambiguousIndexOfImpl; - -// Terminating case encountered once we've checked all of the alternatives -template <class T, std::size_t CurrIndex> -struct UnambiguousIndexOfImpl<variant<>, T, CurrIndex> : SizeT<CurrIndex> {}; - -// Case where T is not Head -template <class Head, class... Tail, class T, std::size_t CurrIndex> -struct UnambiguousIndexOfImpl<variant<Head, Tail...>, T, CurrIndex> - : UnambiguousIndexOfImpl<variant<Tail...>, T, CurrIndex + 1>::type {}; - -// Case where T is Head -template <class Head, class... Tail, std::size_t CurrIndex> -struct UnambiguousIndexOfImpl<variant<Head, Tail...>, Head, CurrIndex> - : SizeT<UnambiguousIndexOfImpl<variant<Tail...>, Head, 0>::value == - sizeof...(Tail) - ? CurrIndex - : CurrIndex + sizeof...(Tail) + 1> {}; - -template <class Variant, class T> -struct UnambiguousIndexOf; - -struct NoMatch { - struct type {}; -}; - -template <class... Alts, class T> -struct UnambiguousIndexOf<variant<Alts...>, T> - : std::conditional<UnambiguousIndexOfImpl<variant<Alts...>, T, 0>::value != - sizeof...(Alts), - UnambiguousIndexOfImpl<variant<Alts...>, T, 0>, - NoMatch>::type::type {}; - -template <class T, std::size_t /*Dummy*/> -using UnambiguousTypeOfImpl = T; - -template <class Variant, class T> -using UnambiguousTypeOfT = - UnambiguousTypeOfImpl<T, UnambiguousIndexOf<Variant, T>::value>; - -template <class H, class... T> -class VariantStateBase; - -// This is an implementation of the "imaginary function" that is described in -// [variant.ctor] -// It is used in order to determine which alternative to construct during -// initialization from some type T. -template <class Variant, std::size_t I = 0> -struct ImaginaryFun; - -template <std::size_t I> -struct ImaginaryFun<variant<>, I> { - static void Run() = delete; -}; - -template <class H, class... T, std::size_t I> -struct ImaginaryFun<variant<H, T...>, I> : ImaginaryFun<variant<T...>, I + 1> { - using ImaginaryFun<variant<T...>, I + 1>::Run; - - // NOTE: const& and && are used instead of by-value due to lack of guaranteed - // move elision of C++17. This may have other minor differences, but tests - // pass. - static SizeT<I> Run(const H&, SizeT<I>); - static SizeT<I> Run(H&&, SizeT<I>); -}; - -// The following metafunctions are used in constructor and assignment -// constraints. -template <class Self, class T> -struct IsNeitherSelfNorInPlace : std::true_type {}; - -template <class Self> -struct IsNeitherSelfNorInPlace<Self, Self> : std::false_type {}; - -template <class Self, class T> -struct IsNeitherSelfNorInPlace<Self, in_place_type_t<T>> : std::false_type {}; - -template <class Self, std::size_t I> -struct IsNeitherSelfNorInPlace<Self, in_place_index_t<I>> : std::false_type {}; - -template <class Variant, class T, class = void> -struct ConversionIsPossibleImpl : std::false_type {}; - -template <class Variant, class T> -struct ConversionIsPossibleImpl< - Variant, T, - void_t<decltype(ImaginaryFun<Variant>::Run(std::declval<T>(), {}))>> - : std::true_type {}; - -template <class Variant, class T> -struct ConversionIsPossible : ConversionIsPossibleImpl<Variant, T>::type {}; - -template <class Variant, class T> -struct IndexOfConstructedType< - Variant, T, - void_t<decltype(ImaginaryFun<Variant>::Run(std::declval<T>(), {}))>> - : decltype(ImaginaryFun<Variant>::Run(std::declval<T>(), {})) {}; - -template <std::size_t... Is> -struct ContainsVariantNPos - : absl::negation<std::is_same< // NOLINT - absl::integer_sequence<bool, 0 <= Is...>, - absl::integer_sequence<bool, Is != absl::variant_npos...>>> {}; - -template <class Op, class... QualifiedVariants> -using RawVisitResult = - absl::result_of_t<Op(VariantAccessResult<0, QualifiedVariants>...)>; - -// NOTE: The spec requires that all return-paths yield the same type and is not -// SFINAE-friendly, so we can deduce the return type by examining the first -// result. If it's not callable, then we get an error, but are compliant and -// fast to compile. -// TODO(calabrese) Possibly rewrite in a way that yields better compile errors -// at the cost of longer compile-times. -template <class Op, class... QualifiedVariants> -struct VisitResultImpl { - using type = - absl::result_of_t<Op(VariantAccessResult<0, QualifiedVariants>...)>; -}; - -// Done in two steps intentionally so that we don't cause substitution to fail. -template <class Op, class... QualifiedVariants> -using VisitResult = typename VisitResultImpl<Op, QualifiedVariants...>::type; - -template <class Op, class... QualifiedVariants> -struct PerformVisitation { - using ReturnType = VisitResult<Op, QualifiedVariants...>; - - template <std::size_t... Is> - constexpr ReturnType operator()(SizeT<Is>... indices) const { - return Run(typename ContainsVariantNPos<Is...>::type{}, - absl::index_sequence_for<QualifiedVariants...>(), indices...); - } - - template <std::size_t... TupIs, std::size_t... Is> - constexpr ReturnType Run(std::false_type /*has_valueless*/, - index_sequence<TupIs...>, SizeT<Is>...) const { - static_assert( - std::is_same<ReturnType, - absl::result_of_t<Op(VariantAccessResult< - Is, QualifiedVariants>...)>>::value, - "All visitation overloads must have the same return type."); - return absl::base_internal::invoke( - absl::forward<Op>(op), - VariantCoreAccess::Access<Is>( - absl::forward<QualifiedVariants>(std::get<TupIs>(variant_tup)))...); - } - - template <std::size_t... TupIs, std::size_t... Is> - [[noreturn]] ReturnType Run(std::true_type /*has_valueless*/, - index_sequence<TupIs...>, SizeT<Is>...) const { - absl::variant_internal::ThrowBadVariantAccess(); - } - - // TODO(calabrese) Avoid using a tuple, which causes lots of instantiations - // Attempts using lambda variadic captures fail on current GCC. - std::tuple<QualifiedVariants&&...> variant_tup; - Op&& op; -}; - -template <class... T> -union Union; - -// We want to allow for variant<> to be trivial. For that, we need the default -// constructor to be trivial, which means we can't define it ourselves. -// Instead, we use a non-default constructor that takes NoopConstructorTag -// that doesn't affect the triviality of the types. -struct NoopConstructorTag {}; - -template <std::size_t I> -struct EmplaceTag {}; - -template <> -union Union<> { - constexpr explicit Union(NoopConstructorTag) noexcept {} -}; - -// Suppress bogus warning on MSVC: MSVC complains that Union<T...> has a defined -// deleted destructor from the `std::is_destructible` check below. -#ifdef _MSC_VER -#pragma warning(push) -#pragma warning(disable : 4624) -#endif // _MSC_VER - -template <class Head, class... Tail> -union Union<Head, Tail...> { - using TailUnion = Union<Tail...>; - - explicit constexpr Union(NoopConstructorTag /*tag*/) noexcept - : tail(NoopConstructorTag()) {} - - template <class... P> - explicit constexpr Union(EmplaceTag<0>, P&&... args) - : head(absl::forward<P>(args)...) {} - - template <std::size_t I, class... P> - explicit constexpr Union(EmplaceTag<I>, P&&... args) - : tail(EmplaceTag<I - 1>{}, absl::forward<P>(args)...) {} - - Head head; - TailUnion tail; -}; - -#ifdef _MSC_VER -#pragma warning(pop) -#endif // _MSC_VER - -// TODO(calabrese) Just contain a Union in this union (certain configs fail). -template <class... T> -union DestructibleUnionImpl; - -template <> -union DestructibleUnionImpl<> { - constexpr explicit DestructibleUnionImpl(NoopConstructorTag) noexcept {} -}; - -template <class Head, class... Tail> -union DestructibleUnionImpl<Head, Tail...> { - using TailUnion = DestructibleUnionImpl<Tail...>; - - explicit constexpr DestructibleUnionImpl(NoopConstructorTag /*tag*/) noexcept - : tail(NoopConstructorTag()) {} - - template <class... P> - explicit constexpr DestructibleUnionImpl(EmplaceTag<0>, P&&... args) - : head(absl::forward<P>(args)...) {} - - template <std::size_t I, class... P> - explicit constexpr DestructibleUnionImpl(EmplaceTag<I>, P&&... args) - : tail(EmplaceTag<I - 1>{}, absl::forward<P>(args)...) {} - - ~DestructibleUnionImpl() {} - - Head head; - TailUnion tail; -}; - -// This union type is destructible even if one or more T are not trivially -// destructible. In the case that all T are trivially destructible, then so is -// this resultant type. -template <class... T> -using DestructibleUnion = - absl::conditional_t<std::is_destructible<Union<T...>>::value, Union<T...>, - DestructibleUnionImpl<T...>>; - -// Deepest base, containing the actual union and the discriminator -template <class H, class... T> -class VariantStateBase { - protected: - using Variant = variant<H, T...>; - - template <class LazyH = H, - class ConstructibleH = absl::enable_if_t< - std::is_default_constructible<LazyH>::value, LazyH>> - constexpr VariantStateBase() noexcept( - std::is_nothrow_default_constructible<ConstructibleH>::value) - : state_(EmplaceTag<0>()), index_(0) {} - - template <std::size_t I, class... P> - explicit constexpr VariantStateBase(EmplaceTag<I> tag, P&&... args) - : state_(tag, absl::forward<P>(args)...), index_(I) {} - - explicit constexpr VariantStateBase(NoopConstructorTag) - : state_(NoopConstructorTag()), index_(variant_npos) {} - - void destroy() {} // Does nothing (shadowed in child if non-trivial) - - DestructibleUnion<H, T...> state_; - std::size_t index_; -}; - -using absl::internal::identity; - -// OverloadSet::Overload() is a unary function which is overloaded to -// take any of the element types of the variant, by reference-to-const. -// The return type of the overload on T is identity<T>, so that you -// can statically determine which overload was called. -// -// Overload() is not defined, so it can only be called in unevaluated -// contexts. -template <typename... Ts> -struct OverloadSet; - -template <typename T, typename... Ts> -struct OverloadSet<T, Ts...> : OverloadSet<Ts...> { - using Base = OverloadSet<Ts...>; - static identity<T> Overload(const T&); - using Base::Overload; -}; - -template <> -struct OverloadSet<> { - // For any case not handled above. - static void Overload(...); -}; - -template <class T> -using LessThanResult = decltype(std::declval<T>() < std::declval<T>()); - -template <class T> -using GreaterThanResult = decltype(std::declval<T>() > std::declval<T>()); - -template <class T> -using LessThanOrEqualResult = decltype(std::declval<T>() <= std::declval<T>()); - -template <class T> -using GreaterThanOrEqualResult = - decltype(std::declval<T>() >= std::declval<T>()); - -template <class T> -using EqualResult = decltype(std::declval<T>() == std::declval<T>()); - -template <class T> -using NotEqualResult = decltype(std::declval<T>() != std::declval<T>()); - -using type_traits_internal::is_detected_convertible; - -template <class... T> -using RequireAllHaveEqualT = absl::enable_if_t< - absl::conjunction<is_detected_convertible<bool, EqualResult, T>...>::value, - bool>; - -template <class... T> -using RequireAllHaveNotEqualT = - absl::enable_if_t<absl::conjunction<is_detected_convertible< - bool, NotEqualResult, T>...>::value, - bool>; - -template <class... T> -using RequireAllHaveLessThanT = - absl::enable_if_t<absl::conjunction<is_detected_convertible< - bool, LessThanResult, T>...>::value, - bool>; - -template <class... T> -using RequireAllHaveLessThanOrEqualT = - absl::enable_if_t<absl::conjunction<is_detected_convertible< - bool, LessThanOrEqualResult, T>...>::value, - bool>; - -template <class... T> -using RequireAllHaveGreaterThanOrEqualT = - absl::enable_if_t<absl::conjunction<is_detected_convertible< - bool, GreaterThanOrEqualResult, T>...>::value, - bool>; - -template <class... T> -using RequireAllHaveGreaterThanT = - absl::enable_if_t<absl::conjunction<is_detected_convertible< - bool, GreaterThanResult, T>...>::value, - bool>; - -// Helper template containing implementations details of variant that can't go -// in the private section. For convenience, this takes the variant type as a -// single template parameter. -template <typename T> -struct VariantHelper; - -template <typename... Ts> -struct VariantHelper<variant<Ts...>> { - // Type metafunction which returns the element type selected if - // OverloadSet::Overload() is well-formed when called with argument type U. - template <typename U> - using BestMatch = decltype( - variant_internal::OverloadSet<Ts...>::Overload(std::declval<U>())); - - // Type metafunction which returns true if OverloadSet::Overload() is - // well-formed when called with argument type U. - // CanAccept can't be just an alias because there is a MSVC bug on parameter - // pack expansion involving decltype. - template <typename U> - struct CanAccept : - std::integral_constant<bool, !std::is_void<BestMatch<U>>::value> {}; - - // Type metafunction which returns true if Other is an instantiation of - // variant, and variants's converting constructor from Other will be - // well-formed. We will use this to remove constructors that would be - // ill-formed from the overload set. - template <typename Other> - struct CanConvertFrom; - - template <typename... Us> - struct CanConvertFrom<variant<Us...>> - : public absl::conjunction<CanAccept<Us>...> {}; -}; - -// A type with nontrivial copy ctor and trivial move ctor. -struct TrivialMoveOnly { - TrivialMoveOnly(TrivialMoveOnly&&) = default; -}; - -// Trait class to detect whether a type is trivially move constructible. -// A union's defaulted copy/move constructor is deleted if any variant member's -// copy/move constructor is nontrivial. -template <typename T> -struct IsTriviallyMoveConstructible: - std::is_move_constructible<Union<T, TrivialMoveOnly>> {}; - -// To guarantee triviality of all special-member functions that can be trivial, -// we use a chain of conditional bases for each one. -// The order of inheritance of bases from child to base are logically: -// -// variant -// VariantCopyAssignBase -// VariantMoveAssignBase -// VariantCopyBase -// VariantMoveBase -// VariantStateBaseDestructor -// VariantStateBase -// -// Note that there is a separate branch at each base that is dependent on -// whether or not that corresponding special-member-function can be trivial in -// the resultant variant type. - -template <class... T> -class VariantStateBaseDestructorNontrivial; - -template <class... T> -class VariantMoveBaseNontrivial; - -template <class... T> -class VariantCopyBaseNontrivial; - -template <class... T> -class VariantMoveAssignBaseNontrivial; - -template <class... T> -class VariantCopyAssignBaseNontrivial; - -// Base that is dependent on whether or not the destructor can be trivial. -template <class... T> -using VariantStateBaseDestructor = - absl::conditional_t<std::is_destructible<Union<T...>>::value, - VariantStateBase<T...>, - VariantStateBaseDestructorNontrivial<T...>>; - -// Base that is dependent on whether or not the move-constructor can be -// implicitly generated by the compiler (trivial or deleted). -// Previously we were using `std::is_move_constructible<Union<T...>>` to check -// whether all Ts have trivial move constructor, but it ran into a GCC bug: -// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84866 -// So we have to use a different approach (i.e. `HasTrivialMoveConstructor`) to -// work around the bug. -template <class... T> -using VariantMoveBase = absl::conditional_t< - absl::disjunction< - absl::negation<absl::conjunction<std::is_move_constructible<T>...>>, - absl::conjunction<IsTriviallyMoveConstructible<T>...>>::value, - VariantStateBaseDestructor<T...>, VariantMoveBaseNontrivial<T...>>; - -// Base that is dependent on whether or not the copy-constructor can be trivial. -template <class... T> -using VariantCopyBase = absl::conditional_t< - absl::disjunction< - absl::negation<absl::conjunction<std::is_copy_constructible<T>...>>, - std::is_copy_constructible<Union<T...>>>::value, - VariantMoveBase<T...>, VariantCopyBaseNontrivial<T...>>; - -// Base that is dependent on whether or not the move-assign can be trivial. -template <class... T> -using VariantMoveAssignBase = absl::conditional_t< - absl::disjunction< - absl::conjunction<absl::is_move_assignable<Union<T...>>, - std::is_move_constructible<Union<T...>>, - std::is_destructible<Union<T...>>>, - absl::negation<absl::conjunction<std::is_move_constructible<T>..., - // Note: We're not qualifying this with - // absl:: because it doesn't compile - // under MSVC. - is_move_assignable<T>...>>>::value, - VariantCopyBase<T...>, VariantMoveAssignBaseNontrivial<T...>>; - -// Base that is dependent on whether or not the copy-assign can be trivial. -template <class... T> -using VariantCopyAssignBase = absl::conditional_t< - absl::disjunction< - absl::conjunction<absl::is_copy_assignable<Union<T...>>, - std::is_copy_constructible<Union<T...>>, - std::is_destructible<Union<T...>>>, - absl::negation<absl::conjunction<std::is_copy_constructible<T>..., - // Note: We're not qualifying this with - // absl:: because it doesn't compile - // under MSVC. - is_copy_assignable<T>...>>>::value, - VariantMoveAssignBase<T...>, VariantCopyAssignBaseNontrivial<T...>>; - -template <class... T> -using VariantBase = VariantCopyAssignBase<T...>; - -template <class... T> -class VariantStateBaseDestructorNontrivial : protected VariantStateBase<T...> { - private: - using Base = VariantStateBase<T...>; - - protected: - using Base::Base; - - VariantStateBaseDestructorNontrivial() = default; - VariantStateBaseDestructorNontrivial(VariantStateBaseDestructorNontrivial&&) = - default; - VariantStateBaseDestructorNontrivial( - const VariantStateBaseDestructorNontrivial&) = default; - VariantStateBaseDestructorNontrivial& operator=( - VariantStateBaseDestructorNontrivial&&) = default; - VariantStateBaseDestructorNontrivial& operator=( - const VariantStateBaseDestructorNontrivial&) = default; - - struct Destroyer { - template <std::size_t I> - void operator()(SizeT<I> i) const { - using Alternative = - typename absl::variant_alternative<I, variant<T...>>::type; - variant_internal::AccessUnion(self->state_, i).~Alternative(); - } - - void operator()(SizeT<absl::variant_npos> /*i*/) const { - // This space intentionally left blank - } - - VariantStateBaseDestructorNontrivial* self; - }; - - void destroy() { VisitIndices<sizeof...(T)>::Run(Destroyer{this}, index_); } - - ~VariantStateBaseDestructorNontrivial() { destroy(); } - - protected: - using Base::index_; - using Base::state_; -}; - -template <class... T> -class VariantMoveBaseNontrivial : protected VariantStateBaseDestructor<T...> { - private: - using Base = VariantStateBaseDestructor<T...>; - - protected: - using Base::Base; - - struct Construct { - template <std::size_t I> - void operator()(SizeT<I> i) const { - using Alternative = - typename absl::variant_alternative<I, variant<T...>>::type; - ::new (static_cast<void*>(&self->state_)) Alternative( - variant_internal::AccessUnion(absl::move(other->state_), i)); - } - - void operator()(SizeT<absl::variant_npos> /*i*/) const {} - - VariantMoveBaseNontrivial* self; - VariantMoveBaseNontrivial* other; - }; - - VariantMoveBaseNontrivial() = default; - VariantMoveBaseNontrivial(VariantMoveBaseNontrivial&& other) noexcept( - absl::conjunction<std::is_nothrow_move_constructible<T>...>::value) - : Base(NoopConstructorTag()) { - VisitIndices<sizeof...(T)>::Run(Construct{this, &other}, other.index_); - index_ = other.index_; - } - - VariantMoveBaseNontrivial(VariantMoveBaseNontrivial const&) = default; - - VariantMoveBaseNontrivial& operator=(VariantMoveBaseNontrivial&&) = default; - VariantMoveBaseNontrivial& operator=(VariantMoveBaseNontrivial const&) = - default; - - protected: - using Base::index_; - using Base::state_; -}; - -template <class... T> -class VariantCopyBaseNontrivial : protected VariantMoveBase<T...> { - private: - using Base = VariantMoveBase<T...>; - - protected: - using Base::Base; - - VariantCopyBaseNontrivial() = default; - VariantCopyBaseNontrivial(VariantCopyBaseNontrivial&&) = default; - - struct Construct { - template <std::size_t I> - void operator()(SizeT<I> i) const { - using Alternative = - typename absl::variant_alternative<I, variant<T...>>::type; - ::new (static_cast<void*>(&self->state_)) - Alternative(variant_internal::AccessUnion(other->state_, i)); - } - - void operator()(SizeT<absl::variant_npos> /*i*/) const {} - - VariantCopyBaseNontrivial* self; - const VariantCopyBaseNontrivial* other; - }; - - VariantCopyBaseNontrivial(VariantCopyBaseNontrivial const& other) - : Base(NoopConstructorTag()) { - VisitIndices<sizeof...(T)>::Run(Construct{this, &other}, other.index_); - index_ = other.index_; - } - - VariantCopyBaseNontrivial& operator=(VariantCopyBaseNontrivial&&) = default; - VariantCopyBaseNontrivial& operator=(VariantCopyBaseNontrivial const&) = - default; - - protected: - using Base::index_; - using Base::state_; -}; - -template <class... T> -class VariantMoveAssignBaseNontrivial : protected VariantCopyBase<T...> { - friend struct VariantCoreAccess; - - private: - using Base = VariantCopyBase<T...>; - - protected: - using Base::Base; - - VariantMoveAssignBaseNontrivial() = default; - VariantMoveAssignBaseNontrivial(VariantMoveAssignBaseNontrivial&&) = default; - VariantMoveAssignBaseNontrivial(const VariantMoveAssignBaseNontrivial&) = - default; - VariantMoveAssignBaseNontrivial& operator=( - VariantMoveAssignBaseNontrivial const&) = default; - - VariantMoveAssignBaseNontrivial& - operator=(VariantMoveAssignBaseNontrivial&& other) noexcept( - absl::conjunction<std::is_nothrow_move_constructible<T>..., - std::is_nothrow_move_assignable<T>...>::value) { - VisitIndices<sizeof...(T)>::Run( - VariantCoreAccess::MakeMoveAssignVisitor(this, &other), other.index_); - return *this; - } - - protected: - using Base::index_; - using Base::state_; -}; - -template <class... T> -class VariantCopyAssignBaseNontrivial : protected VariantMoveAssignBase<T...> { - friend struct VariantCoreAccess; - - private: - using Base = VariantMoveAssignBase<T...>; - - protected: - using Base::Base; - - VariantCopyAssignBaseNontrivial() = default; - VariantCopyAssignBaseNontrivial(VariantCopyAssignBaseNontrivial&&) = default; - VariantCopyAssignBaseNontrivial(const VariantCopyAssignBaseNontrivial&) = - default; - VariantCopyAssignBaseNontrivial& operator=( - VariantCopyAssignBaseNontrivial&&) = default; - - VariantCopyAssignBaseNontrivial& operator=( - const VariantCopyAssignBaseNontrivial& other) { - VisitIndices<sizeof...(T)>::Run( - VariantCoreAccess::MakeCopyAssignVisitor(this, other), other.index_); - return *this; - } - - protected: - using Base::index_; - using Base::state_; -}; - -//////////////////////////////////////// -// Visitors for Comparison Operations // -//////////////////////////////////////// - -template <class... Types> -struct EqualsOp { - const variant<Types...>* v; - const variant<Types...>* w; - - constexpr bool operator()(SizeT<absl::variant_npos> /*v_i*/) const { - return true; - } - - template <std::size_t I> - constexpr bool operator()(SizeT<I> /*v_i*/) const { - return VariantCoreAccess::Access<I>(*v) == VariantCoreAccess::Access<I>(*w); - } -}; - -template <class... Types> -struct NotEqualsOp { - const variant<Types...>* v; - const variant<Types...>* w; - - constexpr bool operator()(SizeT<absl::variant_npos> /*v_i*/) const { - return false; - } - - template <std::size_t I> - constexpr bool operator()(SizeT<I> /*v_i*/) const { - return VariantCoreAccess::Access<I>(*v) != VariantCoreAccess::Access<I>(*w); - } -}; - -template <class... Types> -struct LessThanOp { - const variant<Types...>* v; - const variant<Types...>* w; - - constexpr bool operator()(SizeT<absl::variant_npos> /*v_i*/) const { - return false; - } - - template <std::size_t I> - constexpr bool operator()(SizeT<I> /*v_i*/) const { - return VariantCoreAccess::Access<I>(*v) < VariantCoreAccess::Access<I>(*w); - } -}; - -template <class... Types> -struct GreaterThanOp { - const variant<Types...>* v; - const variant<Types...>* w; - - constexpr bool operator()(SizeT<absl::variant_npos> /*v_i*/) const { - return false; - } - - template <std::size_t I> - constexpr bool operator()(SizeT<I> /*v_i*/) const { - return VariantCoreAccess::Access<I>(*v) > VariantCoreAccess::Access<I>(*w); - } -}; - -template <class... Types> -struct LessThanOrEqualsOp { - const variant<Types...>* v; - const variant<Types...>* w; - - constexpr bool operator()(SizeT<absl::variant_npos> /*v_i*/) const { - return true; - } - - template <std::size_t I> - constexpr bool operator()(SizeT<I> /*v_i*/) const { - return VariantCoreAccess::Access<I>(*v) <= VariantCoreAccess::Access<I>(*w); - } -}; - -template <class... Types> -struct GreaterThanOrEqualsOp { - const variant<Types...>* v; - const variant<Types...>* w; - - constexpr bool operator()(SizeT<absl::variant_npos> /*v_i*/) const { - return true; - } - - template <std::size_t I> - constexpr bool operator()(SizeT<I> /*v_i*/) const { - return VariantCoreAccess::Access<I>(*v) >= VariantCoreAccess::Access<I>(*w); - } -}; - -// Precondition: v.index() == w.index(); -template <class... Types> -struct SwapSameIndex { - variant<Types...>* v; - variant<Types...>* w; - template <std::size_t I> - void operator()(SizeT<I>) const { - type_traits_internal::Swap(VariantCoreAccess::Access<I>(*v), - VariantCoreAccess::Access<I>(*w)); - } - - void operator()(SizeT<variant_npos>) const {} -}; - -// TODO(calabrese) do this from a different namespace for proper adl usage -template <class... Types> -struct Swap { - variant<Types...>* v; - variant<Types...>* w; - - void generic_swap() const { - variant<Types...> tmp(std::move(*w)); - VariantCoreAccess::Destroy(*w); - VariantCoreAccess::InitFrom(*w, std::move(*v)); - VariantCoreAccess::Destroy(*v); - VariantCoreAccess::InitFrom(*v, std::move(tmp)); - } - - void operator()(SizeT<absl::variant_npos> /*w_i*/) const { - if (!v->valueless_by_exception()) { - generic_swap(); - } - } - - template <std::size_t Wi> - void operator()(SizeT<Wi> /*w_i*/) { - if (v->index() == Wi) { - VisitIndices<sizeof...(Types)>::Run(SwapSameIndex<Types...>{v, w}, Wi); - } else { - generic_swap(); - } - } -}; - -template <typename Variant, typename = void, typename... Ts> -struct VariantHashBase { - VariantHashBase() = delete; - VariantHashBase(const VariantHashBase&) = delete; - VariantHashBase(VariantHashBase&&) = delete; - VariantHashBase& operator=(const VariantHashBase&) = delete; - VariantHashBase& operator=(VariantHashBase&&) = delete; -}; - -struct VariantHashVisitor { - template <typename T> - size_t operator()(const T& t) { - return std::hash<T>{}(t); - } -}; - -template <typename Variant, typename... Ts> -struct VariantHashBase<Variant, - absl::enable_if_t<absl::conjunction< - type_traits_internal::IsHashable<Ts>...>::value>, - Ts...> { - using argument_type = Variant; - using result_type = size_t; - size_t operator()(const Variant& var) const { - type_traits_internal::AssertHashEnabled<Ts...>(); - if (var.valueless_by_exception()) { - return 239799884; - } - size_t result = VisitIndices<variant_size<Variant>::value>::Run( - PerformVisitation<VariantHashVisitor, const Variant&>{ - std::forward_as_tuple(var), VariantHashVisitor{}}, - var.index()); - // Combine the index and the hash result in order to distinguish - // std::variant<int, int> holding the same value as different alternative. - return result ^ var.index(); - } -}; - -} // namespace variant_internal -ABSL_NAMESPACE_END -} // namespace absl - -#endif // !defined(ABSL_USES_STD_VARIANT) -#endif // ABSL_TYPES_variant_internal_H_ |