ARC Smart Pointer

This is an implementation of the ARC (Atomic Reference Counting) smart pointer in C++. The ARC smart pointer provides shared ownership of an object using reference counting. It allows multiple pointers to refer to the same object, and the object is deleted only when the last smart pointer referencing it goes out of scope.

Note: This implementation is my personal implementation and may not be 100% accurate or secure. It was developed as a learning exercise to understand the concepts and inner workings of reference counting pointers.

Usage

The ARC smart pointer is provided through two classes: Arc and WeakArc.

Arc

The Arc class represents a strong reference to an object. It provides the following methods:

Constructor

explicit Arc(T *ptr)

• Creates a new Arc instance that manages the given raw pointer ptr.

Copy Constructor

Arc(const Arc &other)

• Creates a new Arc instance as a copy of the other Arc instance.
• Increments the reference count of the control block.

Assignment Operator

Arc &operator=(const Arc &other)

• Assigns the other Arc instance to the current Arc instance.
• Decrements the reference count of the current control block and increments the reference count of the other control block.
• Properly handles self-assignment.

Destructor

~Arc()

• Decrements the reference count of the control block.
• Releases the control block if the reference count reaches zero.

Get Raw Pointer

T *get() const

• Returns the raw pointer to the managed object.

Get Mutex

std::shared_mutex *mutex()

• Returns a pointer to the shared_mutex associated with the control block.

Clone

Arc clone() const

• Creates a new Arc instance as a clone of the current Arc instance.
• Acquires a shared lock on the control block's mutex.

Get Mutable Access

template <typename U> friend U *get_mut(Arc<U> &arc)

• Allows mutable access to the managed object by acquiring a lock on the associated mutex.

WeakArc

The WeakArc class represents a weak reference to an object managed by Arc. It provides the following methods:

Constructor

explicit WeakArc(Arc<T> &arc)

• Creates a new WeakArc instance from an Arc instance.

Copy Constructor

WeakArc(const WeakArc &other)

• Creates a new WeakArc instance as a copy of the other WeakArc instance.
• Increments the reference count of the control block.

Assignment Operator

WeakArc &operator=(const WeakArc &other)

• Assigns the other WeakArc instance to the current WeakArc instance.
• Decrements the reference count of the current control block and increments the reference count of the other control block.

Destructor

~WeakArc()

• Decrements the reference count of the control block.
• Releases the control block if the reference count reaches zero.

Upgrade

Arc<T> upgrade() const

• Upgrades the WeakArc to an Arc instance if the object still exists.
• Returns the upgraded Arc instance or nullptr if the object has been deleted.