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#pragma once
#include "DI/extra_concepts.hpp"
#include <concepts>
#include <tuple>
#include <type_traits>
#include <utility>
// Tag used to default initialize one or both of the pair's elements.
struct DefaultInitTag
{
};
struct ValueInitTag
{
};
template <size_t...>
struct TupleIndices
{
};
template <class IdxType, IdxType... Values>
struct IntegerSequence
{
template <template <class OIdxType, OIdxType...> class ToIndexSeq, class ToIndexType>
using Convert = ToIndexSeq<ToIndexType, Values...>;
template <size_t Sp>
using ToTupleIndices = TupleIndices<(Values + Sp)...>;
};
template <size_t SizeOne, size_t SizeTwo>
using MakeIndices =
typename __make_integer_seq<IntegerSequence, size_t,
SizeOne - SizeTwo>::template ToTupleIndices<SizeTwo>;
template <size_t SizeOne, size_t SizeTwo = 0>
requires(SizeTwo <= SizeOne) struct MakeTupleIndices
{
using type = MakeIndices<SizeOne, SizeTwo>;
};
template <typename Value>
concept ValueCanBeEmptyBase = std::is_empty_v<Value> && !std::is_final_v<Value>;
template <class Value, int Idx>
struct CompressedPairElement
{
using ValueReference = Value &;
using ConstValueReference = const Value &;
constexpr explicit CompressedPairElement(DefaultInitTag /*unused*/) {}
constexpr explicit CompressedPairElement(ValueInitTag /*unused*/) : _value() {}
template <class ElementValue>
requires std::same_as<CompressedPairElement, typename std::decay<ElementValue>::type>
// NOLINTNEXTLINE(bugprone-forwarding-reference-overload)
constexpr explicit CompressedPairElement(ElementValue &&value)
: _value(std::forward<ElementValue>(value))
{
}
template <class... Args, size_t... Indexes>
constexpr CompressedPairElement(std::piecewise_construct_t /*unused*/,
std::tuple<Args...> args,
TupleIndices<Indexes...> /*unused*/)
: _value(std::forward<Args>(std::get<Indexes>(args))...)
{
}
auto get() noexcept -> ValueReference
{
return _value;
}
[[nodiscard]] auto get() const noexcept -> ConstValueReference
{
return _value;
}
private:
Value _value;
};
template <class Value, int Idx>
requires ValueCanBeEmptyBase<Value>
struct CompressedPairElement<Value, Idx> : private Value
{
using ValueReference = Value &;
using ConstValueReference = const Value &;
constexpr CompressedPairElement() = default;
constexpr explicit CompressedPairElement(DefaultInitTag /*unused*/) {}
constexpr explicit CompressedPairElement(ValueInitTag /*unused*/) : Value() {}
template <class ElementValue>
requires std::same_as<CompressedPairElement, typename std::decay<ElementValue>::type>
// NOLINTNEXTLINE(bugprone-forwarding-reference-overload)
constexpr explicit CompressedPairElement(ElementValue &&value)
: Value(std::forward<ElementValue>(value))
{
}
template <class... Args, size_t... Indexes>
constexpr CompressedPairElement(std::piecewise_construct_t /*unused*/,
std::tuple<Args...> args,
TupleIndices<Indexes...> /*unused*/)
: Value(std::forward<Args>(std::get<Indexes>(args))...)
{
}
auto get() noexcept -> ValueReference
{
return *this;
}
[[nodiscard]] auto get() const noexcept -> ConstValueReference
{
return *this;
}
};
template <class ValueOne, class ValueTwo>
requires NotSameAs<ValueOne, ValueTwo>
class CompressedPair : private CompressedPairElement<ValueOne, 0>,
private CompressedPairElement<ValueTwo, 1>
{
public:
using BaseOne = CompressedPairElement<ValueOne, 0>;
using BaseTwo = CompressedPairElement<ValueTwo, 1>;
template <typename>
requires std::default_initializable<ValueOne> && std::default_initializable<ValueTwo>
constexpr CompressedPair() : BaseOne(ValueInitTag()), BaseTwo(ValueInitTag()) {}
template <class FirstValue, class SecondValue>
constexpr CompressedPair(FirstValue &&first_value, SecondValue &&second_value)
: BaseOne(std::forward<FirstValue>(first_value)),
BaseTwo(std::forward<SecondValue>(second_value))
{
}
template <class... ArgsOne, class... ArgsTwo>
constexpr CompressedPair(std::piecewise_construct_t piecewise_construct,
std::tuple<ArgsOne...> first_args,
std::tuple<ArgsTwo...> second_args)
: BaseOne(piecewise_construct, std::move(first_args),
typename MakeTupleIndices<sizeof...(ArgsOne)>::type()),
BaseTwo(piecewise_construct, std::move(second_args),
typename MakeTupleIndices<sizeof...(ArgsTwo)>::type())
{
}
auto first() noexcept -> typename BaseOne::ValueReference
{
return static_cast<BaseOne &>(*this).get();
}
[[nodiscard]] auto first() const noexcept -> typename BaseOne::ConstValueReference
{
return static_cast<BaseOne const &>(*this).get();
}
auto second() noexcept -> typename BaseTwo::ValueReference
{
return static_cast<BaseTwo &>(*this).get();
}
[[nodiscard]] auto second() const noexcept -> typename BaseTwo::ConstValueReference
{
return static_cast<BaseTwo const &>(*this).get();
}
constexpr static auto get_first_base(CompressedPair *pair) noexcept -> BaseOne *
{
return static_cast<BaseOne *>(pair);
}
constexpr static auto get_second_base(CompressedPair *pair) noexcept -> BaseTwo *
{
return static_cast<BaseTwo *>(pair);
}
};
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