indirectly_readable_traits.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2023 Tobias Hienzsch
 
#ifndef TETL_ITERATOR_INDIRECTLY_READABLE_TRAITS_HPP
#define TETL_ITERATOR_INDIRECTLY_READABLE_TRAITS_HPP
 
#include <etl/_concepts/same_as.hpp>
#include <etl/_type_traits/is_array.hpp>
#include <etl/_type_traits/is_object.hpp>
#include <etl/_type_traits/remove_cv.hpp>
#include <etl/_type_traits/remove_extent.hpp>
 
namespace etl {
 
namespace detail {
 
template <typename>
struct maybe_value_type { };
 
template <typename T>
    requires etl::is_object_v<T>
struct maybe_value_type<T> {
    using value_type = etl::remove_cv_t<T>;
};
 
template <typename T>
concept has_member_value_type = requires { typename T::value_type; };
 
template <typename T>
concept has_member_element_type = requires { typename T::element_type; };
 
} // namespace detail
 
template <typename I>
struct indirectly_readable_traits { };
 
template <typename T>
struct indirectly_readable_traits<T const> : indirectly_readable_traits<T> { };
 
template <typename T>
struct indirectly_readable_traits<T*> : detail::maybe_value_type<T> { };
 
template <typename I>
    requires etl::is_array_v<I>
struct indirectly_readable_traits<I> {
    using value_type = etl::remove_cv_t<etl::remove_extent_t<I>>;
};
 
template <detail::has_member_value_type T>
struct indirectly_readable_traits<T> : detail::maybe_value_type<typename T::value_type> { };
 
template <detail::has_member_element_type T>
struct indirectly_readable_traits<T> : detail::maybe_value_type<typename T::element_type> { };
 
template <detail::has_member_value_type T>
    requires detail::has_member_element_type<T>
struct indirectly_readable_traits<T> { };
 
template <detail::has_member_value_type T>
    requires(
        detail::has_member_element_type<T>
        and etl::same_as<etl::remove_cv_t<typename T::element_type>, etl::remove_cv_t<typename T::value_type>>
    )
struct indirectly_readable_traits<T> : detail::maybe_value_type<typename T::value_type> { };
 
} // namespace etl
 
#endif // TETL_ITERATOR_INDIRECTLY_READABLE_TRAITS_HPP