A C++ smart pointer for CoreFoundation objects

PSPDFHigherOrderFunctions.hpp

// hpp:

/// A smart pointer that can manage the lifecycle of Core Foundation objects.
template<typename T>
class CFPointer {
public:
    CFPointer() : storage(nullptr) { }

    CFPointer(T pointer) : storage(toStorageType(pointer)) {
        if (storage) {
            CFRetain(storage);
        }
    }

    CFPointer(const CFPointer & other) : storage(other.storage) {
        if (CFTypeRef ptr = storage) {
            CFRetain(ptr);
        }
    }

    CFPointer(CFPointer && other) : storage(std::exchange(other.storage, nullptr)) { }

    ~CFPointer() {
        if (CFTypeRef pointer = storage) {
            CFRelease(pointer);
        }
    }

    static inline CFPointer<T> adopt(T CF_RELEASES_ARGUMENT ptr);

    T get() const;
    CFPointer &operator=(CFPointer);

private:
    CFTypeRef storage;

    enum AdoptTag { Adopt };
    CFPointer(T ptr, AdoptTag) : storage(toStorageType(ptr)) { }

    inline CFTypeRef toStorageType(CFTypeRef ptr) const {
        return (CFTypeRef)ptr;
    }

    inline T fromStorageType(CFTypeRef pointer) const {
        return (T)pointer;
    }

    void swap(CFPointer &);
};

template<typename T>
CFPointer<T> CFPointer<T>::adopt(T CF_RELEASES_ARGUMENT ptr) {
    return CFPointer<T>(ptr, CFPointer<T>::Adopt);
}

template<typename T>
T CFPointer<T>::get() const {
    return fromStorageType(storage);
}

template<typename T>
inline CFPointer<T>& CFPointer<T>::operator=(CFPointer other) {
    swap(other);
    return *this;
}

template<typename T>
inline void CFPointer<T>::swap(CFPointer &other) {
    std::swap(storage, other.storage);
}


// cpp:

/// A smart pointer that can manage the lifecycle of Core Foundation objects.
template<typename T>
class CFPointer {
public:
    CFPointer() : storage(nullptr) { }

    CFPointer(T pointer) : storage(toStorageType(pointer)) {
        if (storage) {
            CFRetain(storage);
        }
    }

    CFPointer(const CFPointer & other) : storage(other.storage) {
        if (CFTypeRef ptr = storage) {
            CFRetain(ptr);
        }
    }

    CFPointer(CFPointer && other) : storage(std::exchange(other.storage, nullptr)) { }

    ~CFPointer() {
        if (CFTypeRef pointer = storage) {
            CFRelease(pointer);
        }
    }

    static inline CFPointer<T> adopt(T CF_RELEASES_ARGUMENT ptr);

    T get() const;
    CFPointer &operator=(CFPointer);

private:
    CFTypeRef storage;

    enum AdoptTag { Adopt };
    CFPointer(T ptr, AdoptTag) : storage(toStorageType(ptr)) { }

    inline CFTypeRef toStorageType(CFTypeRef ptr) const {
        return (CFTypeRef)ptr;
    }

    inline T fromStorageType(CFTypeRef pointer) const {
        return (T)pointer;
    }

    void swap(CFPointer &);
};

template<typename T>
CFPointer<T> CFPointer<T>::adopt(T CF_RELEASES_ARGUMENT ptr) {
    return CFPointer<T>(ptr, CFPointer<T>::Adopt);
}

template<typename T>
T CFPointer<T>::get() const {
    return fromStorageType(storage);
}

template<typename T>
inline CFPointer<T>& CFPointer<T>::operator=(CFPointer other) {
    swap(other);
    return *this;
}

template<typename T>
inline void CFPointer<T>::swap(CFPointer &other) {
    std::swap(storage, other.storage);
}

@steipete, I just watched your AltConf lecture - thanks for the tips! Is there any specific reason you've re-implemented unique_ptr instead of just implementing a custom deleter (or a specialization of std::default_delete) that calls CFRelease?