Id.hpp

// Copyright (c) 2025 Devexperts LLC.
// SPDX-License-Identifier: MPL-2.0
 
#pragma once
 
#include "./Conf.hpp"
 
DXFCXX_DISABLE_MSC_WARNINGS_PUSH(4251)
 
#include <atomic>
#include <cstdint>
 
DXFCPP_BEGIN_NAMESPACE
 
template <typename T> struct Id {
    using ValueType = std::size_t;
    const static Id UNKNOWN;
 
    private:
    ValueType value_{};
 
    explicit Id(ValueType value) : value_{value} {
    }
 
    public:
    static Id<T> getNext() {
        static std::atomic<ValueType> value(1);
 
        return Id<T>{value++};
    }
 
    [[nodiscard]] ValueType getValue() const {
        return value_;
    }
 
    explicit operator ValueType() const {
        return value_;
    }
 
    static Id<T> from(ValueType value) {
        return Id<T>{value};
    }
 
    template <typename H> static Id<T> from(H *handle) {
        return Id<T>{dxfcpp::bit_cast<ValueType>(handle)};
    }
 
    template <typename H> static Id<T> from(const H *handle) {
        return Id<T>{dxfcpp::bit_cast<ValueType>(handle)};
    }
 
    template <typename U> bool operator==(const Id<U> &id) const {
        return getValue() == id.getValue();
    }
 
    template <typename U> auto operator<=>(const Id<U> &id) const {
        return getValue() <=> id.getValue();
    }
};
 
template <typename T> const Id<T> Id<T>::UNKNOWN{static_cast<Id<T>::ValueType>(-1)};
 
DXFCPP_END_NAMESPACE
 
template <typename T> struct std::hash<dxfcpp::Id<T>> {
    std::size_t operator()(const dxfcpp::Id<T> &id) const noexcept {
        return id.getValue();
    }
};
 
DXFCXX_DISABLE_MSC_WARNINGS_POP()