ref_view.h

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#pragma once
 
#include "di/container/concepts/contiguous_container.h"
#include "di/container/concepts/has_empty_container.h"
#include "di/container/concepts/sized_container.h"
#include "di/container/interface/empty.h"
#include "di/container/interface/reconstruct.h"
#include "di/container/meta/enable_borrowed_container.h"
#include "di/container/view/view_interface.h"
#include "di/meta/language.h"
#include "di/meta/util.h"
#include "di/util/declval.h"
#include "di/util/forward.h"
#include "di/util/reference_wrapper.h"
 
namespace di::container {
template<concepts::Container Cont>
requires(concepts::Object<Cont>)
class RefView
    : public ViewInterface<RefView<Cont>>
    , public meta::EnableBorrowedContainer<RefView<Cont>> {
private:
    template<typename X>
    constexpr static void delete_rvalues(X&);
 
public:
    template<typename X>
    constexpr static void delete_rvalues(X&&) = delete;
 
    template<typename T>
    requires(!concepts::DecaySameAs<T, RefView> && requires { delete_rvalues(util::declval<T>()); })
    constexpr RefView(T&& container) : m_container(static_cast<Cont&>(util::forward<T>(container))) {}
 
    constexpr auto base() const -> Cont& { return m_container.get(); }
 
    constexpr auto begin() const { return container::begin(m_container.get()); }
    constexpr auto end() const { return container::end(m_container.get()); }
 
    constexpr auto empty() const -> bool
    requires(concepts::HasEmptyContainer<Cont>)
    {
        return container::empty(m_container.get());
    }
 
    constexpr auto size() const
    requires(concepts::SizedContainer<Cont>)
    {
        return container::size(m_container.get());
    }
 
    constexpr auto data() const
    requires(concepts::ContiguousContainer<Cont>)
    {
        return container::data(m_container.get());
    }
 
private:
    template<typename T, typename U>
    requires(!concepts::SameAs<RefView, Cont> &&
             concepts::Invocable<decltype(container::reconstruct), InPlaceType<Cont>, T, U>)
    constexpr friend auto tag_invoke(types::Tag<container::reconstruct>, InPlaceType<RefView>, T&& t, U&& u) {
        return container::reconstruct(in_place_type<Cont>, util::forward<T>(t), util::forward<U>(u));
    }
 
    util::ReferenceWrapper<Cont> m_container;
};
 
template<typename Cont>
RefView(Cont&) -> RefView<Cont>;
}