ImplicitSurfaceNetwork/shared_module/utils/marked_ptr.hpp

#pragma once

#include <cstddef>

template <typename T, size_t bits_to_store>
struct marked_ptr {
    static constexpr size_t mask = (1 << bits_to_store) - 1;

    // static_assert(alignof(T) >= (1 << bits_to_store));

    marked_ptr(T* ptr = nullptr) : ptr(ptr) {}

    marked_ptr(T* ptr, size_t mark) : ptr((T*)((size_t)ptr | (mark & mask))) {}

    T* get_ptr() const { return (T*)((size_t)ptr & ~1); }

    size_t get_mark() const { return (size_t)ptr & mask; }

    void set_ptr(T* ptr) { this->ptr = (T*)((size_t)ptr | get_mark()); }

    void set_mark(size_t mark) { ptr = (T*)(((size_t)ptr & ~mask) | (mark & mask)); }

    operator T*() const { return get_ptr(); }

    operator size_t() const { return get_mark(); }

    T* operator->() const noexcept { return get_ptr(); }

protected:
    T* ptr{nullptr};
};

// template <typename T>
// struct marked_ptr<T, 1> {
//     // static_assert(alignof(T) >= 1);

//     marked_ptr(T* ptr = nullptr) : ptr(ptr) {}

//     marked_ptr(T* ptr, bool mark) : ptr((T*)((size_t)ptr | mark)) {}

//     T* get_ptr() const { return (T*)((size_t)ptr & ~1); }

//     bool is_marked() const { return (size_t)ptr & 1; }

//     void set_ptr(T* ptr) { this->ptr = (T*)((size_t)ptr | is_marked()); }

//     void set_mark(bool mark) { ptr = (T*)((size_t)ptr | mark); }

//     operator T*() const { return get_ptr(); }

//     operator bool() const { return is_marked(); }

//     T* operator->() const { return get_ptr(); }

// protected:
//     T* ptr{nullptr};
// };

template <typename F, typename T, size_t bits_to_store>
inline static marked_ptr<F, bits_to_store> static_pointer_cast(const marked_ptr<T, bits_to_store>& p)
{
    return marked_ptr<F, bits_to_store>(static_cast<F*>(p.get_ptr()), p.get_mark());
}