pointer_like_traits.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2021 Tobias Hienzsch
 
#ifndef TETL_MEMORY_POINTER_LIKE_TRAITS_HPP
#define TETL_MEMORY_POINTER_LIKE_TRAITS_HPP
 
#include <etl/_cstddef/size_t.hpp>
#include <etl/_cstdint/uintptr_t.hpp>
#include <etl/_math/ilog2.hpp>
 
namespace etl {
 
/// \brief A traits type that is used to handle pointer types and things that
/// are just wrappers for pointers as a uniform entity.
template <typename T>
struct pointer_like_traits;
 
/// \brief Provide pointer_like_traits for non-cvr pointers.
template <typename T>
struct pointer_like_traits<T*> {
    [[nodiscard]] static auto get_as_void_pointer(T* p) -> void*
    {
        return p;
    }
 
    [[nodiscard]] static auto get_from_void_pointer(void* p) -> T*
    {
        return static_cast<T*>(p);
    }
 
    static constexpr size_t free_bits = ilog2(alignof(T));
};
 
/// Provide pointer_like_traits for const things.
template <typename T>
struct pointer_like_traits<T const> {
    using non_const = pointer_like_traits<T>;
 
    [[nodiscard]] static auto get_as_void_pointer(T const p) -> void const*
    {
        return non_const::get_as_void_pointer(p);
    }
 
    // NOLINTNEXTLINE(readability-const-return-type)
    [[nodiscard]] static auto get_from_void_pointer(void const* p) -> T const
    {
        return non_const::get_from_void_pointer(const_cast<void*>(p));
    }
 
    static constexpr size_t free_bits = non_const::free_bits;
};
 
/// Provide pointer_like_traits for const pointers.
template <typename T>
struct pointer_like_traits<T const*> {
    using non_const = pointer_like_traits<T*>;
 
    [[nodiscard]] static auto get_as_void_pointer(T const* p) -> void const*
    {
        return non_const::get_as_void_pointer(const_cast<T*>(p));
    }
 
    [[nodiscard]] static auto get_from_void_pointer(void const* p) -> T const*
    {
        return non_const::get_from_void_pointer(const_cast<void*>(p));
    }
 
    static constexpr size_t free_bits = non_const::free_bits;
};
 
/// Provide pointer_like_traits for uintptr_t.
template <>
struct pointer_like_traits<uintptr_t> {
    [[nodiscard]] static auto get_as_void_pointer(uintptr_t p) -> void*
    {
        return bit_cast<void*>(p);
    }
 
    [[nodiscard]] static auto get_from_void_pointer(void* p) -> uintptr_t
    {
        return bit_cast<uintptr_t>(p);
    }
 
    // No bits are available!
    static constexpr size_t free_bits = 0;
};
 
} // namespace etl
 
#endif // TETL_MEMORY_POINTER_LIKE_TRAITS_HPP