native_handle.hpp

/*
 * Copyright (c) 2024 The RefValue Project
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#pragma once
 
#include <compare>
#include <concepts>
#include <cstdint>
 
namespace essence {
    template <typename T>
    concept handle_stroage_type = std::integral<T> && sizeof(T) >= sizeof(std::uintptr_t);
 
    template <auto Callable, typename T>
    concept handle_validator_type = requires {
        requires std::integral<T>;
        { Callable } -> std::predicate<T>;
    };
 
    template <std::integral T>
    T make_pointer_number(const void* pointer) noexcept {
        return static_cast<T>(reinterpret_cast<std::uintptr_t>(pointer));
    }
 
    template <std::integral T>
    constexpr bool is_valid_handle_value(T value) noexcept {
        return value != 0 && value != -1;
    }
 
    template <handle_stroage_type T = std::uintptr_t, typename Mapped = T,
        auto Validator = &is_valid_handle_value<Mapped>>
        requires handle_validator_type<Validator, Mapped>
    class basic_native_handle {
    public:
        constexpr basic_native_handle(std::nullptr_t = nullptr) noexcept : value_{} {} // NOLINT(*-explicit-constructor)
 
        template <typename U>
            requires std::is_pointer_v<U>
        basic_native_handle(U value) noexcept : value_{make_pointer_number<T>(value)} {} // NOLINT(*-explicit-constructor)
 
        constexpr basic_native_handle(Mapped value) noexcept : value_{static_cast<T>(value)} {} // NOLINT(*-explicit-constructor)
 
        constexpr bool operator==(const basic_native_handle&) const noexcept  = default;
        constexpr auto operator<=>(const basic_native_handle&) const noexcept = default;
 
        explicit constexpr operator bool() const noexcept {
            return Validator(static_cast<Mapped>(value_));
        }
 
        template <typename U>
            requires std::is_pointer_v<U>
        operator U() const noexcept { // NOLINT(*-explicit-constructor)
            return reinterpret_cast<U>(value_);
        }
 
        constexpr operator Mapped() const noexcept { // NOLINT(*-explicit-constructor)
            return static_cast<Mapped>(value_);
        }
 
    private:
        T value_;
    };
 
    using native_handle = basic_native_handle<>;
} // namespace essence