shared_ptr.hpp

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#ifndef NEFORCE_CORE_MEMORY_SHARED_PTR_HPP__
#define NEFORCE_CORE_MEMORY_SHARED_PTR_HPP__

 
#include <new>
#include "NeForce/core/algorithm/compare.hpp"
#include "NeForce/core/async/atomic.hpp"
#include "NeForce/core/exception/exception.hpp"
#include "NeForce/core/memory/allocator_traits.hpp"
#include "NeForce/core/memory/unique_ptr.hpp"
NEFORCE_BEGIN_NAMESPACE__


NEFORCE_BEGIN_INNER__
 
template <typename T>
class smart_pointer_atomic;
 

struct __smart_ptr_counter {
public:
    atomic<unsigned long> strong_count_; 
    atomic<unsigned long> weak_count_;   
 
protected:
    virtual void delete_object() = 0;

    virtual void delete_this() = 0;
 
public:
    __smart_ptr_counter() noexcept :
    strong_count_(1),
    weak_count_(1) {}
 
    __smart_ptr_counter(__smart_ptr_counter&&) = delete; 
 
    virtual ~__smart_ptr_counter() = default; 

    void incref_strong() noexcept { strong_count_.fetch_add(1, memory_order_relaxed); }

    void incref_weak() noexcept { weak_count_.fetch_add(1, memory_order_relaxed); }

    void decref_strong() noexcept {
        if (strong_count_.fetch_sub(1, memory_order_acq_rel) == 1) {
            delete_object();
            decref_weak();
        }
    }

    void decref_weak() noexcept {
        if (weak_count_.fetch_sub(1, memory_order_acq_rel) == 1) {
            delete_this();
        }
    }

    bool try_incref_strong() noexcept {
        auto strong = strong_count_.load(memory_order_relaxed);
        do {
            if (strong == 0) {
                return false;
            }
        } while (!strong_count_.compare_exchange_weak(strong, strong + 1, memory_order_release, memory_order_relaxed));
        return true;
    }

    NEFORCE_NODISCARD uint64_t use_count() const noexcept { return strong_count_.load(memory_order_relaxed); }

    NEFORCE_NODISCARD uint64_t weak_count() const noexcept { return weak_count_.load(memory_order_relaxed); }
};

template <typename T, typename Deleter>
struct __smart_ptr_counter_impl final : __smart_ptr_counter {
    compressed_pair<Deleter, T*> ptr_pair_{default_construct_tag{}, nullptr};
 
    static_assert(is_invocable_v<Deleter, T*>, "Deleter must be invocable by T*");
 
    explicit __smart_ptr_counter_impl(T* ptr) noexcept(is_nothrow_default_constructible_v<Deleter>) :
    ptr_pair_(default_construct_tag{}, ptr) {}
 
    explicit __smart_ptr_counter_impl(T* ptr, Deleter&& deleter) noexcept(is_nothrow_move_constructible_v<Deleter>) :
    ptr_pair_(exact_arg_construct_tag{}, _NEFORCE move(deleter), ptr) {}
 
    void delete_object() override {
        ptr_pair_.get_base()(ptr_pair_.value);
        ptr_pair_.value = nullptr;
    }
 
    void delete_this() noexcept override { delete this; }
};

template <typename T, typename Deleter>
struct __smart_ptr_counter_impl_fused final : __smart_ptr_counter {
    compressed_pair<Deleter, T*> ptr_pair_{default_construct_tag{}, nullptr};
    size_t align_;
    void* mem_;
 
    explicit __smart_ptr_counter_impl_fused(T* ptr, void* mem, size_t align, Deleter deleter) noexcept :
    ptr_pair_(exact_arg_construct_tag{}, _NEFORCE move(deleter), ptr),
    align_(align),
    mem_(mem) {}
 
    void delete_object() noexcept override {
        ptr_pair_.get_base()(ptr_pair_.value);
        ptr_pair_.value = nullptr;
    }
 
    void delete_this() noexcept override {
#if NEFORCE_STANDARD_17
        operator delete(mem_, std::align_val_t{align_});
#else
        operator delete(mem_);
#endif
    }
};

template <typename T, typename Deleter, typename Alloc>
struct __smart_ptr_counter_impl_allocated final : __smart_ptr_counter {
    compressed_pair<Deleter, T*> ptr_pair_{default_construct_tag{}, nullptr};
    compressed_pair<Alloc, size_t> size_pair_{default_construct_tag{}, 0};
    void* mem_;
 
    explicit __smart_ptr_counter_impl_allocated(T* ptr, void* mem, const size_t size, Deleter deleter,
                                                Alloc alloc) noexcept :
    ptr_pair_(exact_arg_construct_tag{}, _NEFORCE move(deleter), ptr),
    size_pair_(exact_arg_construct_tag{}, _NEFORCE move(alloc), size),
    mem_(mem) {}
 
    void delete_object() noexcept override {
        ptr_pair_.get_base()(ptr_pair_.value);
        ptr_pair_.value = nullptr;
    }
 
    void delete_this() noexcept override {
        using alloc_traits = allocator_traits<Alloc>;
        using byte_allocator = typename alloc_traits::template alloc_rebind_t<Alloc, byte_t>;
        byte_allocator byte_alloc(size_pair_.get_base());
        allocator_traits<byte_allocator>::deallocate(byte_alloc, static_cast<byte_t*>(mem_), size_pair_.value);
    }
};
 
NEFORCE_END_INNER__
 
 
template <typename T>
struct enable_shared_from;
 
template <typename T>
class shared_ptr;
 
template <typename T>
class weak_ptr;

NEFORCE_BEGIN_INNER__
 
template <typename T>
void __setup_enable_shared_from_impl(T* ptr, __smart_ptr_counter* owner, true_type) noexcept {
    if (ptr) {
        static_cast<enable_shared_from<T>*>(ptr)->owner_ = owner;
    }
}
 
template <typename T>
void __setup_enable_shared_from_impl(T*, __smart_ptr_counter*, false_type) noexcept {}
 
template <typename T>
void __setup_enable_shared_from(T* ptr, __smart_ptr_counter* owner) noexcept {
    inner::__setup_enable_shared_from_impl(ptr, owner, is_base_of<enable_shared_from<T>, T>{});
}
 
template <typename T>
shared_ptr<T> __make_shared_fused(T* ptr, __smart_ptr_counter* owner) noexcept {
    return shared_ptr<T>(ptr, owner);
}
 
NEFORCE_END_INNER__
 

template <typename T>
class shared_ptr {
public:
    using element_type = T; 
 
private:
    using owner_type = inner::__smart_ptr_counter;
 
    template <typename U, typename Deleter>
    using owner_deleter = inner::__smart_ptr_counter_impl<U, Deleter>;
 
    template <typename U>
    using owner_default = inner::__smart_ptr_counter_impl<U, default_delete<U>>;
 
    element_type* ptr_ = nullptr; 
    owner_type* owner_ = nullptr; 

    explicit shared_ptr(T* ptr, owner_type* owner) noexcept :
    ptr_(ptr),
    owner_(owner) {}
 
    template <typename U>
    friend class shared_ptr;
 
    template <typename U>
    friend class weak_ptr;
 
    template <typename U>
    friend class inner::smart_pointer_atomic;
 
    template <typename U>
    friend shared_ptr<U> inner::__make_shared_fused(U*, inner::__smart_ptr_counter*) noexcept;
 
public:
    shared_ptr(nullptr_t np = nullptr) noexcept {}

    template <typename U, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    shared_ptr(U* ptr) :
    ptr_(ptr),
    owner_(new owner_default<U>(ptr_)) {
        inner::__setup_enable_shared_from(ptr_, owner_);
    }

    template <typename U, typename Deleter, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    explicit shared_ptr(U* ptr, Deleter&& deleter) :
    ptr_(ptr),
    owner_(new owner_deleter<U, Deleter>(ptr_, _NEFORCE forward<Deleter>(deleter))) {
        inner::__setup_enable_shared_from(ptr_, owner_);
    }

    template <typename U, typename Deleter, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    explicit shared_ptr(unique_ptr<U, Deleter>&& unique) :
    shared_ptr(unique.release(), unique.get_deleter()) {}

    shared_ptr(const shared_ptr& other) noexcept :
    ptr_(other.ptr_),
    owner_(other.owner_) {
        if (owner_) {
            owner_->incref_strong();
        }
    }

    shared_ptr& operator=(const shared_ptr& other) noexcept {
        if (_NEFORCE addressof(other) == this) {
            return *this;
        }
        if (owner_) {
            owner_->decref_strong();
        }
        ptr_ = other.ptr_;
        owner_ = other.owner_;
        if (owner_) {
            owner_->incref_strong();
        }
        return *this;
    }

    template <typename U, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    shared_ptr(const shared_ptr<U>& other) noexcept :
    ptr_(other.ptr_),
    owner_(other.owner_) {
        if (owner_) {
            owner_->incref_strong();
        }
    }

    shared_ptr(shared_ptr&& other) noexcept :
    ptr_(other.ptr_),
    owner_(other.owner_) {
        other.ptr_ = nullptr;
        other.owner_ = nullptr;
    }

    shared_ptr& operator=(shared_ptr&& other) noexcept {
        if (_NEFORCE addressof(other) == this) {
            return *this;
        }
        if (owner_) {
            owner_->decref_strong();
        }
        ptr_ = other.ptr_;
        owner_ = other.owner_;
        other.ptr_ = nullptr;
        other.owner_ = nullptr;
        return *this;
    }

    template <typename U, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    explicit shared_ptr(shared_ptr<U>&& other) noexcept :
    ptr_(other.ptr_),
    owner_(other.owner_) {
        other.ptr_ = nullptr;
        other.owner_ = nullptr;
    }

    template <typename U>
    shared_ptr(const shared_ptr<U>& other, T* ptr) noexcept :
    ptr_(ptr),
    owner_(other.owner_) {
        if (owner_) {
            owner_->incref_strong();
        }
    }

    template <typename U>
    shared_ptr(shared_ptr<U>&& other, T* ptr) noexcept :
    ptr_(ptr),
    owner_(other.owner_) {
        other.ptr_ = nullptr;
        other.owner_ = nullptr;
    }

    template <typename U, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    shared_ptr& operator=(const shared_ptr<U>& other) noexcept {
        if (owner_) {
            owner_->decref_strong();
        }
        ptr_ = other.ptr_;
        owner_ = other.owner_;
        if (owner_) {
            owner_->incref_strong();
        }
        return *this;
    }

    template <typename U, enable_if_t<is_convertible_v<U*, T*>, int> = 0>
    shared_ptr& operator=(shared_ptr<U>&& other) noexcept {
        if (owner_) {
            owner_->decref_strong();
        }
        ptr_ = other.ptr_;
        owner_ = other.owner_;
        other.ptr_ = nullptr;
        other.owner_ = nullptr;
        return *this;
    }

    ~shared_ptr() noexcept { reset(); }

    void reset() noexcept {
        if (owner_) {
            owner_->decref_strong();
        }
        owner_ = nullptr;
        ptr_ = nullptr;
    }

    template <typename U>
    void reset(U* ptr) {
        if (owner_) {
            owner_->decref_strong();
        }
        ptr_ = nullptr;
        owner_ = nullptr;
        ptr_ = ptr;
        owner_ = new owner_default<U>(ptr_);
        inner::__setup_enable_shared_from<T>(ptr_, owner_);
    }

    template <typename U, typename Deleter>
    void reset(U* ptr, Deleter deleter) {
        if (owner_) {
            owner_->decref_strong();
        }
        ptr_ = nullptr;
        owner_ = nullptr;
        ptr_ = ptr;
        owner_ = new owner_deleter<U, Deleter>(ptr_, _NEFORCE move(deleter));
        inner::__setup_enable_shared_from<T>(ptr_, owner_);
    }

    NEFORCE_NODISCARD long use_count() const noexcept { return owner_ ? owner_->use_count() : 0; }

    NEFORCE_NODISCARD bool unique() const noexcept { return owner_ ? owner_->use_count() == 1 : true; }

    void swap(shared_ptr& other) noexcept {
        if (_NEFORCE addressof(other) == this) {
            return;
        }
        _NEFORCE swap(ptr_, other.ptr_);
        _NEFORCE swap(owner_, other.owner_);
    }

    NEFORCE_NODISCARD T* get() const noexcept { return ptr_; }

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

    NEFORCE_NODISCARD add_lvalue_reference_t<T> operator*() const noexcept { return *ptr_; }

    NEFORCE_NODISCARD explicit operator bool() const noexcept { return ptr_ != nullptr; }

    template <typename U>
    NEFORCE_NODISCARD bool owner_equal(const shared_ptr<U>& rhs) const noexcept {
        return owner_ == rhs.owner_;
    }

    template <typename U>
    NEFORCE_NODISCARD bool owner_equal(const weak_ptr<U>& rhs) const noexcept {
        return owner_ == rhs.owner_;
    }

    template <typename U>
    NEFORCE_NODISCARD bool owner_before(const shared_ptr<U>& rhs) const noexcept {
        return owner_ < rhs.owner_;
    }

    template <typename U>
    NEFORCE_NODISCARD bool owner_before(const weak_ptr<U>& rhs) const noexcept {
        return owner_ < rhs.owner_;
    }
};

template <typename T, typename U>
NEFORCE_NODISCARD bool operator==(const shared_ptr<T>& lhs, const shared_ptr<U>& rhs) noexcept {
    return lhs.owner_equal(rhs);
}

template <typename T, typename U>
NEFORCE_NODISCARD bool operator!=(const shared_ptr<T>& lhs, const shared_ptr<U>& rhs) noexcept {
    return !(lhs == rhs);
}

template <typename T, typename U>
NEFORCE_NODISCARD bool operator<(const shared_ptr<T>& lhs, const shared_ptr<U>& rhs) noexcept {
    return lhs.owner_before(rhs);
}

template <typename T, typename U>
NEFORCE_NODISCARD bool operator>(const shared_ptr<T>& lhs, const shared_ptr<U>& rhs) noexcept {
    return rhs < lhs;
}

template <typename T, typename U>
NEFORCE_NODISCARD bool operator<=(const shared_ptr<T>& lhs, const shared_ptr<U>& rhs) noexcept {
    return !(lhs > rhs);
}

template <typename T, typename U>
NEFORCE_NODISCARD bool operator>=(const shared_ptr<T>& lhs, const shared_ptr<U>& rhs) noexcept {
    return !(lhs < rhs);
}
 

template <typename T>
class shared_ptr<T[]> : shared_ptr<T> {
public:
    using shared_ptr<T>::shared_ptr;

    add_lvalue_reference_t<T> operator[](size_t idx) { return this->get()[idx]; }
};
 

template <typename T>
struct enable_shared_from {
private:
    mutable inner::__smart_ptr_counter* owner_ = nullptr; 
 
    template <typename U>
    friend void inner::__setup_enable_shared_from_impl(U* ptr, inner::__smart_ptr_counter* owner, true_type) noexcept;
 
    template <typename U>
    friend void inner::__setup_enable_shared_from(U*, inner::__smart_ptr_counter*) noexcept;
 
    template <typename U>
    friend class shared_ptr;
 
    template <typename U>
    friend class weak_ptr;
 
protected:
    enable_shared_from() noexcept {}

    shared_ptr<T> shared_from_this() {
        static_assert(is_base_of_v<enable_shared_from, T>, "shared from T requires derived class");
        if (!owner_) {
            NEFORCE_THROW_EXCEPTION(memory_exception("smart pointer share failed."));
        }
        owner_->incref_strong();
        return inner::__make_shared_fused(static_cast<T*>(this), owner_);
    }

    shared_ptr<const T> shared_from_this() const {
        static_assert(is_base_of_v<enable_shared_from, T>, "shared from T requires derived class");
        if (!owner_) {
            NEFORCE_THROW_EXCEPTION(memory_exception("smart pointer share failed."));
        }
        owner_->incref_strong();
        return inner::__make_shared_fused(static_cast<const T*>(this), owner_);
    }
};
 

template <typename T>
struct is_shared_ptr : false_type {};
 
template <typename T>
struct is_shared_ptr<shared_ptr<T>> : true_type {};
 
template <typename T>
NEFORCE_INLINE17 constexpr bool is_shared_ptr_v = is_shared_ptr<T>::value;
 

template <typename T, typename... Args>
enable_if_t<!is_unbounded_array_v<T> && is_constructible_v<T, Args...>, shared_ptr<T>> make_shared(Args&&... args) {
    auto const deleter = [](T* ptr) noexcept(is_nothrow_destructible_v<T>) { ptr->~T(); };
    using Counter = inner::__smart_ptr_counter_impl_fused<T, decltype(deleter)>;
    constexpr size_t align = max(alignof(T), alignof(Counter));
    constexpr size_t offset = (sizeof(Counter) + align - 1) & ~(align - 1);
    constexpr size_t size = offset + sizeof(T);
#if NEFORCE_STANDARD_17
    void* mem = operator new(size, std::align_val_t{align});
    auto* counter = static_cast<Counter*>(mem);
#else
    void* mem = operator new(size + align - 1);
    size_t aligned_addr = (reinterpret_cast<size_t>(mem) + (align - 1)) & ~(align - 1);
    Counter* counter = reinterpret_cast<Counter*>(aligned_addr);
#endif
    T* object = reinterpret_cast<T*>(reinterpret_cast<byte_t*>(counter) + offset);
    try {
        _NEFORCE construct(object, _NEFORCE forward<Args>(args)...);
    } catch (...) {
#if NEFORCE_STANDARD_17
        operator delete(mem, std::align_val_t{align});
#else
        operator delete(mem);
#endif
        NEFORCE_THROW_EXCEPTION(memory_exception("shared ptr construction failed."));
    }
    _NEFORCE construct(reinterpret_cast<Counter*>(counter), object, mem, align, _NEFORCE move(deleter));
    inner::__setup_enable_shared_from(object, counter);
    return inner::__make_shared_fused(object, counter);
}

template <typename T>
enable_if_t<is_unbounded_array_v<T>, shared_ptr<T>> make_shared(const size_t len) {
    using value = remove_extent_t<T>;
    value* tmp = nullptr;
    try {
        tmp = new value[len];
        return shared_ptr<T[]>(tmp, default_delete<value[]>{});
    } catch (...) {
        operator delete[](tmp);
        NEFORCE_THROW_EXCEPTION(memory_exception("shared ptr construction failed."));
    }
    unreachable();
}

template <typename T, typename Alloc, typename... Args>
enable_if_t<!is_array_v<T> && is_constructible_v<T, Args...>, shared_ptr<T>> allocate_shared(Alloc& alloc,
                                                                                             Args&&... args) {
    auto deleter = [](T* p) { p->~T(); };
    using ControlBlock = inner::__smart_ptr_counter_impl_allocated<T, decltype(deleter), Alloc>;
 
    const size_t align = _NEFORCE max(alignof(ControlBlock), alignof(T));
    const size_t offset = (sizeof(ControlBlock) + align - 1) & ~(align - 1);
    const size_t total_size = offset + sizeof(T);
    const size_t raw_size = total_size + align - 1;
 
    using alloc_traits = allocator_traits<remove_cv_t<Alloc>>;
    using byte_allocator = typename alloc_traits::template alloc_rebind_t<Alloc, byte_t>;
    byte_allocator byte_alloc(alloc);
 
    byte_t* raw_mem = allocator_traits<byte_allocator>::allocate(byte_alloc, raw_size);
 
    const uintptr_t raw_addr = reinterpret_cast<uintptr_t>(raw_mem);
    const uintptr_t aligned_addr = (raw_addr + align - 1) & ~static_cast<uintptr_t>(align - 1);
    auto aligned_mem = reinterpret_cast<byte_t*>(aligned_addr);
    T* object_ptr = reinterpret_cast<T*>(aligned_mem + offset);
 
    try {
        allocator_traits<Alloc>::construct(alloc, object_ptr, _NEFORCE forward<Args>(args)...);
    } catch (...) {
        allocator_traits<byte_allocator>::deallocate(byte_alloc, raw_mem, raw_size);
        NEFORCE_THROW_EXCEPTION(memory_exception("shared ptr ref object construction failed."));
    }
 
    ControlBlock* ctrl_block = nullptr;
    try {
        ctrl_block = _NEFORCE construct(reinterpret_cast<ControlBlock*>(aligned_mem), object_ptr, raw_mem, raw_size,
                                        deleter, alloc);
    } catch (...) {
        allocator_traits<Alloc>::destroy(alloc, object_ptr);
        allocator_traits<byte_allocator>::deallocate(byte_alloc, raw_mem, raw_size);
        NEFORCE_THROW_EXCEPTION(memory_exception("shared ptr control block construction failed."));
    }
 
    inner::__setup_enable_shared_from(object_ptr, ctrl_block);
    return inner::__make_shared_fused(object_ptr, ctrl_block);
}
 

template <typename T, typename U>
shared_ptr<T> static_pointer_cast(const shared_ptr<U>& ptr) {
    return shared_ptr<T>(ptr, static_cast<T*>(ptr.get()));
}

template <typename T, typename U>
shared_ptr<T> const_pointer_cast(const shared_ptr<U>& ptr) {
    return shared_ptr<T>(ptr, const_cast<T*>(ptr.get()));
}

template <typename T, typename U>
shared_ptr<T> reinterpret_pointer_cast(const shared_ptr<U>& ptr) {
    return shared_ptr<T>(ptr, reinterpret_cast<T*>(ptr.get()));
}

template <typename T, typename U>
shared_ptr<T> dynamic_pointer_cast(const shared_ptr<U>& ptr) {
    T* tmp = dynamic_cast<T*>(ptr.get());
    if (tmp != nullptr) {
        return shared_ptr<T>(ptr, tmp);
    }
    return nullptr;
}
 // SharedPointer


template <typename T>
struct hash<shared_ptr<T>> {
    NEFORCE_CONSTEXPR20 size_t operator()(const shared_ptr<T>& ptr) const
            noexcept(noexcept(_NEFORCE declval<_NEFORCE hash<T*>>()(_NEFORCE declval<T*>()))) {
        return hash<T*>()(ptr.get());
    }
};
 // HashPrimary

NEFORCE_BEGIN_INNER__
 
template <typename T>
class smart_pointer_atomic {
public:
    using value_type = T;
 
private:
    struct atomic_counter {
    public:
        using count_type = inner::__smart_ptr_counter;
 
    private:
        mutable atomic_base<uintptr_t> value_{0};
 
        static constexpr uintptr_t lock_bit{1};
 
        static void dereference(count_type* counter, true_type) noexcept { counter->decref_strong(); }
 
        static void dereference(count_type* counter, false_type) noexcept { counter->decref_weak(); }
 
    public:
        constexpr atomic_counter() noexcept = default;
 
        explicit atomic_counter(count_type* counter) noexcept :
        value_(reinterpret_cast<uintptr_t>(counter)) {
            counter = nullptr;
        }
 
        ~atomic_counter() {
            auto value = value_.load(memory_order_relaxed);
            NEFORCE_CONSTEXPR_ASSERT(!(value & lock_bit));
            if (auto counter = reinterpret_cast<count_type*>(value)) {
                this->dereference(counter, is_shared_ptr<T>());
            }
        }
 
        atomic_counter(const atomic_counter&) = delete;
        atomic_counter& operator=(const atomic_counter&) = delete;
 
        count_type* lock(memory_order mo) const noexcept {
            if (mo != memory_order_seq_cst) {
                mo = memory_order_acquire;
            }
            auto cur = value_.load(memory_order_relaxed);
            while (cur & lock_bit) {
                this_thread::relax();
                cur = value_.load(memory_order_relaxed);
            }
 
            while (!value_.compare_exchange_strong(cur, cur | lock_bit, mo, memory_order_relaxed)) {
                this_thread::relax();
                cur = cur & ~lock_bit;
            }
            return reinterpret_cast<count_type*>(cur);
        }
 
        void unlock(memory_order mo) const noexcept { value_.fetch_sub(1, mo); }
 
        count_type* swap_unlock(count_type* counter, memory_order mo) noexcept {
            if (mo != memory_order_seq_cst) {
                mo = memory_order_release;
            }
            auto addr = reinterpret_cast<uintptr_t>(counter);
            addr = value_.exchange(addr, mo);
            return reinterpret_cast<count_type*>(addr & ~lock_bit);
        }
 
        void wait_unlock(memory_order mo) const noexcept {
            const auto old_value = value_.load(memory_order_relaxed);
            const auto unlocked = old_value & ~lock_bit;
            value_.fetch_sub(1, memory_order_release);
            if (value_.load(memory_order_acquire) == unlocked) {
                value_.wait(unlocked, mo);
            }
        }
 
        void notify_one() noexcept { value_.notify_one(); }
 
        void notify_all() noexcept { value_.notify_all(); }
    };
 
    typename T::element_type* ptr_ = nullptr;
    atomic_counter refcount_;
 
    friend struct atomic<T>;
 
private:
    static typename atomic_counter::count_type* incref(typename atomic_counter::count_type* counter, true_type) {
        if (counter) {
            counter->incref_strong();
        }
        return counter;
    }
 
    static typename atomic_counter::count_type* incref(typename atomic_counter::count_type* counter, false_type) {
        if (counter) {
            counter->incref_weak();
        }
        return counter;
    }
 
public:
    constexpr smart_pointer_atomic() noexcept = default;
 
    explicit smart_pointer_atomic(value_type value) noexcept :
    ptr_(value.ptr_),
    refcount_(value.owner_) {
        value.owner_ = nullptr;
        value.ptr_ = nullptr;
    }
 
    ~smart_pointer_atomic() = default;
 
    smart_pointer_atomic(const smart_pointer_atomic&) = delete;
    void operator=(const smart_pointer_atomic&) = delete;
 
    value_type load(memory_order mo) const noexcept {
        NEFORCE_CONSTEXPR_ASSERT(mo != memory_order_release && mo != memory_order_acq_rel);
        if (mo != memory_order_seq_cst) {
            mo = memory_order_acquire;
        }
 
        value_type value;
        auto counter = refcount_.lock(mo);
        value.ptr_ = ptr_;
        value.owner_ = this->incref(counter, is_shared_ptr<T>());
        refcount_.unlock(memory_order_relaxed);
        return value;
    }
 
    void swap(value_type& value, memory_order mo) noexcept {
        refcount_.lock(memory_order_acquire);
        _NEFORCE swap(ptr_, value.ptr_);
        auto* old_owner = refcount_.swap_unlock(value.owner_, mo);
        value.owner_ = old_owner;
    }
 
    bool compare_exchange_strong(value_type& expected, value_type desired, memory_order mo1,
                                 memory_order mo2) noexcept {
        bool result = true;
        auto* counter = refcount_.lock(memory_order_acquire);
        if (ptr_ == expected.ptr_ && counter == expected.owner_) {
            ptr_ = desired.ptr_;
            auto* old_owner = refcount_.swap_unlock(desired.owner_, mo1);
            desired.owner_ = old_owner;
        } else {
            auto* new_counter = this->incref(counter, is_shared_ptr<T>());
            refcount_.unlock(mo2);
            expected.ptr_ = ptr_;
            expected.owner_ = new_counter;
            result = false;
        }
        return result;
    }
 
    void wait(value_type mold, memory_order mo) const noexcept {
        auto* counter = refcount_.lock(memory_order_acquire);
        if (ptr_ == mold.ptr_ && counter == mold.owner_) {
            refcount_.wait_unlock(mo);
        } else {
            refcount_.unlock(memory_order_relaxed);
        }
    }
 
    void notify_one() noexcept { refcount_.notify_one(); }
 
    void notify_all() noexcept { refcount_.notify_all(); }
};
 
NEFORCE_END_INNER__


template <typename T>
struct atomic<shared_ptr<T>> {
public:
    using value_type = shared_ptr<T>;
 
    static constexpr bool is_always_lock_free = false;
 
private:
    inner::smart_pointer_atomic<value_type> atomic_;
 
public:
    bool is_lock_free() const noexcept { return false; }

    constexpr atomic(nullptr_t = nullptr) noexcept {}

    atomic(value_type value) noexcept :
    atomic_(move(value)) {}
 
    atomic(const atomic&) = delete;
    void operator=(const atomic&) = delete;

    value_type load(memory_order mo = memory_order_seq_cst) const noexcept { return atomic_.load(mo); }

    operator value_type() const noexcept { return atomic_.load(memory_order_seq_cst); }

    void store(value_type desired, memory_order mo = memory_order_seq_cst) noexcept { atomic_.swap(desired, mo); }

    void operator=(value_type desired) noexcept { atomic_.swap(desired, memory_order_seq_cst); }

    void operator=(nullptr_t) noexcept { store(nullptr); }

    value_type exchange(value_type desired, memory_order mo = memory_order_seq_cst) noexcept {
        atomic_.swap(desired, mo);
        return desired;
    }

    bool compare_exchange_strong(value_type& expected, value_type desired, memory_order mo, memory_order mo2) noexcept {
        return atomic_.compare_exchange_strong(expected, desired, mo, mo2);
    }

    bool compare_exchange_strong(value_type& expected, value_type desired,
                                 memory_order mo = memory_order_seq_cst) noexcept {
        return compare_exchange_strong(expected, move(desired), mo, cmpexch_failure_order(mo));
    }

    bool compare_exchange_weak(value_type& expected, value_type desired, memory_order mo, memory_order mo2) noexcept {
        return compare_exchange_strong(expected, move(desired), mo, mo2);
    }

    bool compare_exchange_weak(value_type& expected, value_type desired,
                               memory_order mo = memory_order_seq_cst) noexcept {
        return compare_exchange_strong(expected, move(desired), mo);
    }

    void wait(value_type mold, memory_order mo = memory_order_seq_cst) const noexcept { atomic_.wait(move(mold), mo); }

    void notify_one() noexcept { atomic_.notify_one(); }

    void notify_all() noexcept { atomic_.notify_all(); }
};
 // AtomicOperations
 
NEFORCE_END_NAMESPACE__
#endif // NEFORCE_CORE_MEMORY_SHARED_PTR_HPP__