mijin2/source/mijin/memory/dynamic_pointer.hpp

#pragma once

#if !defined(MIJIN_MEMORY_DYNAMIC_POINTER_HPP_INCLUDED)
#define MIJIN_MEMORY_DYNAMIC_POINTER_HPP_INCLUDED 1

#include <bit>
#include <cstdint>
#include <utility>

#include "../internal/common.hpp"
#include "../memory/memutil.hpp"
#include "../util/concepts.hpp"
#include "../util/flag.hpp"

namespace mijin
{
MIJIN_DEFINE_FLAG(Owning);

template<typename T, deleter_type<T> TDeleter = std::default_delete<T>>
class DynamicPointer
{
public:
    using pointer = T*;
    using element_type = T;
    using deleter_t = TDeleter;
private:
    std::uintptr_t mData = 0;
    [[no_unique_address]] TDeleter mDeleter;
public:
    constexpr DynamicPointer(std::nullptr_t = nullptr) MIJIN_NOEXCEPT {}
    DynamicPointer(const DynamicPointer&) = delete;
    constexpr DynamicPointer(pointer ptr, Owning owning, TDeleter deleter = {}) MIJIN_NOEXCEPT_IF(std::is_nothrow_move_constructible_v<TDeleter>)
        : mData(std::bit_cast<std::uintptr_t>(ptr) | (owning ? 1 : 0)), mDeleter(std::move(deleter))
    {
        MIJIN_ASSERT((std::bit_cast<std::uintptr_t>(ptr) & 1) == 0, "Invalid address, DynamicPointer requires addresses to be divisible by two.");
    }
    template<typename TOther, typename TOtherDeleter> requires (std::is_constructible_v<TDeleter, TOtherDeleter&&>)
    constexpr DynamicPointer(DynamicPointer<TOther, TOtherDeleter>&& other) MIJIN_NOEXCEPT_IF((std::is_nothrow_convertible_v<TOtherDeleter, TDeleter>))
        : mData(std::exchange(other.mData, 0)), mDeleter(std::move(other.mDeleter)) {
        MIJIN_ASSERT(other.mData == 0, "");
    }
    constexpr ~DynamicPointer() noexcept
    {
        reset();
    }

    DynamicPointer& operator=(const DynamicPointer&) = delete;
    DynamicPointer& operator=(std::nullptr_t) MIJIN_NOEXCEPT
    {
        reset();
        return *this;
    }

    template<typename TOther, typename TOtherDeleter> requires(std::is_assignable_v<TDeleter, TOtherDeleter>)
    DynamicPointer& operator=(DynamicPointer<TOther, TOtherDeleter>&& other) MIJIN_NOEXCEPT_IF((std::is_nothrow_assignable_v<TDeleter, TOtherDeleter>))
    {
        if (this != &other)
        {
            reset();
            mData = std::exchange(other.mData, 0);
            mDeleter = std::move(other.mDeleter);
        }
        return *this;
    }

    template<typename TOther, typename TOtherDeleter> requires(std::equality_comparable_with<T, TOther>)
    auto operator<=>(const DynamicPointer<TOther, TOtherDeleter>& other) MIJIN_NOEXCEPT
    {
        return mData <=> other.mData;
    }

    constexpr bool operator==(std::nullptr_t) const MIJIN_NOEXCEPT
    {
        return empty();
    }

    constexpr bool operator!=(std::nullptr_t) const MIJIN_NOEXCEPT
    {
        return !empty();
    }

    constexpr operator bool() const MIJIN_NOEXCEPT
    {
        return !empty();
    }

    constexpr bool operator!() const MIJIN_NOEXCEPT
    {
        return empty();
    }

    constexpr pointer operator->() const MIJIN_NOEXCEPT
    {
        return get();
    }

    constexpr element_type& operator*() const MIJIN_NOEXCEPT
    {
        return *get();
    }

    [[nodiscard]]
    constexpr bool isOwning() const MIJIN_NOEXCEPT
    {
        return (mData & 1) == 1;
    }

    [[nodiscard]]
    constexpr bool empty() const MIJIN_NOEXCEPT
    {
        return mData == 0;
    }

    [[nodiscard]]
    constexpr pointer get() const MIJIN_NOEXCEPT
    {
        return std::bit_cast<pointer>(mData & ~1);
    }

    constexpr void reset(pointer ptr, Owning owning) MIJIN_NOEXCEPT
    {
        if (isOwning())
        {
            mDeleter(get());
        }
        mData = std::bit_cast<std::uintptr_t>(ptr) | (owning ? 1 : 0);
    }

    constexpr void reset() MIJIN_NOEXCEPT
    {
        reset(nullptr, Owning::NO);
    }

    [[nodiscard]]
    pointer release() MIJIN_NOEXCEPT
    {
        return std::bit_cast<pointer>(std::exchange(mData, 0) & ~1);
    }

    template<typename TOther, deleter_type<TOther> TOtherDeleter>
    friend class DynamicPointer;
};

template<typename T, typename TDeleter>
bool operator==(std::nullptr_t, const DynamicPointer<T, TDeleter>& pointer) MIJIN_NOEXCEPT
{
    return pointer == nullptr;
}

template<typename T, typename TDeleter>
bool operator!=(std::nullptr_t, const DynamicPointer<T, TDeleter>& pointer) MIJIN_NOEXCEPT
{
    return pointer != nullptr;
}

template<typename T, typename... TArgs>
DynamicPointer<T, std::default_delete<T>> makeDynamic(TArgs&&... args) MIJIN_NOEXCEPT_IF((std::is_nothrow_constructible_v<T, TArgs...>))
{
    return DynamicPointer<T, std::default_delete<T>>(new T(std::forward<TArgs>(args)...), Owning::YES);
}

template<typename T, allocator_type_for<T> TAllocator, typename... TArgs>
DynamicPointer<T, AllocatorDeleter<TAllocator>> makeDynamicWithAllocator(TAllocator allocator, TArgs&&... args)
        MIJIN_NOEXCEPT_IF((std::is_nothrow_constructible_v<T, TArgs...> && std::is_nothrow_move_constructible_v<TAllocator>))
{
    T* obj = allocator.allocate(1);
    if (obj != nullptr)
    {
        ::new(obj) T(std::forward<TArgs>(args)...);
    }
    return DynamicPointer<T, AllocatorDeleter<TAllocator>>(obj, Owning::YES, AllocatorDeleter<TAllocator>(std::move(allocator)));
}
} // namespace mijin

#endif // !defined(MIJIN_MEMORY_DYNAMIC_POINTER_HPP_INCLUDED)