hyprutils/include/hyprutils/memory/SharedPtr.hpp

#pragma once

#include "ImplBase.hpp"

/*
    This is a custom impl of std::shared_ptr.
    It is not thread-safe like the STL one,
    but Hyprland is single-threaded anyways.

    It differs a bit from how the STL one works,
    namely in the fact that it keeps the T* inside the
    control block, and that you can still make a CWeakPtr
    or deref an existing one inside the destructor.
*/

namespace Hyprutils {
    namespace Memory {

        template <typename T>
        class CSharedPointer {
          public:
            template <typename X>
            using validHierarchy = typename std::enable_if<std::is_assignable<CSharedPointer<T>&, X>::value, CSharedPointer&>::type;
            template <typename X>
            using isConstructible = typename std::enable_if<std::is_constructible<T&, X&>::value>::type;

            /* creates a new shared pointer managing a resource
               avoid calling. Could duplicate ownership. Prefer makeShared */
            explicit CSharedPointer(T* object) noexcept {
                impl_ = new Impl_::impl<T>(object);
                increment();
            }

            /* creates a shared pointer from a reference */
            template <typename U, typename = isConstructible<U>>
            CSharedPointer(const CSharedPointer<U>& ref) noexcept {
                impl_ = ref.impl_;
                increment();
            }

            CSharedPointer(const CSharedPointer& ref) noexcept {
                impl_ = ref.impl_;
                increment();
            }

            template <typename U, typename = isConstructible<U>>
            CSharedPointer(CSharedPointer<U>&& ref) noexcept {
                std::swap(impl_, ref.impl_);
            }

            CSharedPointer(CSharedPointer&& ref) noexcept {
                std::swap(impl_, ref.impl_);
            }

            /* allows weakPointer to create from an impl */
            CSharedPointer(Impl_::impl_base* implementation) noexcept {
                impl_ = implementation;
                increment();
            }

            /* creates an empty shared pointer with no implementation */
            CSharedPointer() noexcept {
                ; // empty
            }

            /* creates an empty shared pointer with no implementation */
            CSharedPointer(std::nullptr_t) noexcept {
                ; // empty
            }

            ~CSharedPointer() {
                decrement();
            }

            template <typename U>
            validHierarchy<const CSharedPointer<U>&> operator=(const CSharedPointer<U>& rhs) {
                if (impl_ == rhs.impl_)
                    return *this;

                decrement();
                impl_ = rhs.impl_;
                increment();
                return *this;
            }

            CSharedPointer& operator=(const CSharedPointer& rhs) {
                if (impl_ == rhs.impl_)
                    return *this;

                decrement();
                impl_ = rhs.impl_;
                increment();
                return *this;
            }

            template <typename U>
            validHierarchy<const CSharedPointer<U>&> operator=(CSharedPointer<U>&& rhs) {
                std::swap(impl_, rhs.impl_);
                return *this;
            }

            CSharedPointer& operator=(CSharedPointer&& rhs) {
                std::swap(impl_, rhs.impl_);
                return *this;
            }

            operator bool() const {
                return impl_ && impl_->dataNonNull();
            }

            bool operator==(const CSharedPointer& rhs) const {
                return impl_ == rhs.impl_;
            }

            bool operator()(const CSharedPointer& lhs, const CSharedPointer& rhs) const {
                return reinterpret_cast<uintptr_t>(lhs.impl_) < reinterpret_cast<uintptr_t>(rhs.impl_);
            }

            bool operator<(const CSharedPointer& rhs) const {
                return reinterpret_cast<uintptr_t>(impl_) < reinterpret_cast<uintptr_t>(rhs.impl_);
            }

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

            T& operator*() const {
                return *get();
            }

            void reset() {
                decrement();
                impl_ = nullptr;
            }

            T* get() const {
                return impl_ ? static_cast<T*>(impl_->getData()) : nullptr;
            }

            unsigned int strongRef() const {
                return impl_ ? impl_->ref() : 0;
            }

            Impl_::impl_base* impl_ = nullptr;

          private:
            /* 
                no-op if there is no impl_
                may delete the stored object if ref == 0
                may delete and reset impl_ if ref == 0 and weak == 0
            */
            void decrement() {
                if (!impl_)
                    return;

                impl_->dec();

                // if ref == 0, we can destroy impl
                if (impl_->ref() == 0)
                    destroyImpl();
            }
            /* no-op if there is no impl_ */
            void increment() {
                if (!impl_)
                    return;

                impl_->inc();
            }

            /* destroy the pointed-to object 
               if able, will also destroy impl */
            void destroyImpl() {
                // destroy the impl contents
                impl_->destroy();

                // check for weak refs, if zero, we can also delete impl_
                if (impl_->wref() == 0) {
                    delete impl_;
                    impl_ = nullptr;
                }
            }
        };

        template <typename U, typename... Args>
        static CSharedPointer<U> makeShared(Args&&... args) {
            return CSharedPointer<U>(new U(std::forward<Args>(args)...));
        }
    }
}

template <typename T>
struct std::hash<Hyprutils::Memory::CSharedPointer<T>> {
    std::size_t operator()(const Hyprutils::Memory::CSharedPointer<T>& p) const noexcept {
        return std::hash<void*>{}(p.impl_);
    }
};