weakptr.h

// Description: WeakPtr class
// Detail: A non-counting smart-pointer to breaking cyclic references
// Documentation: countedptr.txt

#ifndef PASTELSYS_WEAKPTR_H
#define PASTELSYS_WEAKPTR_H

#include "pastel/sys/mytypes.h"
#include "pastel/sys/pointer/countedptr/referencecounted.h"
#include "pastel/sys/hashing.h"

#include <compare>

namespace Pastel
{

    template <typename Type>
    class CountedPtr;

    //! A non-counting smart-pointer
    template <typename Type>
    class WeakPtr
    {
    public:
        template <typename ThatType>
        friend class WeakPtr;

        //! Constructs an empty pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        WeakPtr();

        //! Constructs a copy of the given pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        WeakPtr(const WeakPtr<Type>& that);

        //! Constructs a copy of the given pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow

       Note implicit conversion is allowed.
       */
        template <typename ThatType>
        WeakPtr(const WeakPtr<ThatType>& that);

        template <typename ThatType>
        WeakPtr(const CountedPtr<ThatType>& that);

        //! Constructs a copy of the given pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        explicit WeakPtr(Type* that);

        //! Destructs the pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        ~WeakPtr();

        //! Copies the given pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        WeakPtr<Type>& operator=(
            const WeakPtr<Type>& that);

        //! Copies the given pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        template <typename ThatType>
        WeakPtr<Type>& operator=(
            const WeakPtr<ThatType>& that);

        //! Copies the given pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        WeakPtr<Type>& operator=(Type* that);

        //! Compares two pointers.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        template <typename ThatType>
        auto operator<=>(const WeakPtr<ThatType>& that) const {
            return data_ <=> that.data_;
        }

        //! Returns the contained pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        Type* get() const;

        //! Dereferences the object pointed to.
        /*!
       Preconditions:
       !empty()

       Time complexity: constant
       Exception safety: nothrow
       */
        Type* operator->() const;

        //! Dereferences the object pointed to.
        /*!
       Preconditions:
       !empty()

       Time complexity: constant
       Exception safety: nothrow
       */
        Type& operator*() const;

        //! Swaps two pointers.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        void swap(WeakPtr<Type>& that);

        //! Sets the current pointer to null pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        void clear();

        //! Returns the number of active WeakPtr's to the current pointee.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        integer count() const;

        //! Returns true if this object points to a null pointer.
        /*!
       Time complexity: constant
       Exception safety: nothrow
       */
        bool empty() const;

    private:
        Type* data_;
    };

    template <typename Type>
    void swap(WeakPtr<Type>& left,
        WeakPtr<Type>& right);

}

namespace std
{

    template <typename Type>
    struct hash<Pastel::WeakPtr<Type>>
    {
    public:
        Pastel::hash_integer operator()(
            const Pastel::WeakPtr<Type>& that) const
        {
            return Pastel::computeHash(that.get());
        }
    };

}

#include "pastel/sys/pointer/weakptr/weakptr.hpp"

#endif