Acore::Impl::MPSCQueueNonIntrusive< T > Class Template Reference

C++ implementation of Dmitry Vyukov's lock-free MPSC queue (Non-Intrusive). More...

#include "MPSCQueue.h"

Classes
struct	Node
	A structure representing a node in the queue. More...

Public Member Functions
	MPSCQueueNonIntrusive ()
	Constructs a new MPSCQueueNonIntrusive object.
	~MPSCQueueNonIntrusive ()
	Destroys the MPSCQueueNonIntrusive object.
void	Enqueue (T *input)
	Enqueues a new item in the queue.
bool	Dequeue (T *&result)
	Dequeues an item from the queue.

Private Member Functions
	MPSCQueueNonIntrusive (MPSCQueueNonIntrusive const &)=delete
	Deleted copy constructor.
MPSCQueueNonIntrusive &	operator= (MPSCQueueNonIntrusive const &)=delete
	Deleted copy assignment operator.

Private Attributes
std::atomic< Node * >	_head
	Atomic pointer to the head node of the queue.
std::atomic< Node * >	_tail
	Atomic pointer to the tail node of the queue.

Detailed Description

template<typename T>
class Acore::Impl::MPSCQueueNonIntrusive< T >

C++ implementation of Dmitry Vyukov's lock-free MPSC queue (Non-Intrusive).

This queue allows multiple producers to enqueue items concurrently, but only one consumer can dequeue items. The queue is lock-free and non-intrusive, meaning it does not modify the data types that are enqueued.

Template Parameters

T	The type of data that is being enqueued in the queue.

Constructor & Destructor Documentation

MPSCQueueNonIntrusive() [1/2]

template<typename T >

Acore::Impl::MPSCQueueNonIntrusive< T >::MPSCQueueNonIntrusive ( )

inline

Constructs a new MPSCQueueNonIntrusive object.

Initializes the queue with a dummy node and sets up atomic pointers to the head and tail.

< Store with release to ensure visibility

            : _head(new Node(nullptr)), _tail(_head.load(std::memory_order_acquire))
        {
            Node* front = _head.load(std::memory_order_acquire);
            front->Next.store(nullptr, std::memory_order_release);  
        }

References Acore::Impl::MPSCQueueNonIntrusive< T >::_head, and Acore::Impl::MPSCQueueNonIntrusive< T >::Node::Next.

~MPSCQueueNonIntrusive()

template<typename T >

Acore::Impl::MPSCQueueNonIntrusive< T >::~MPSCQueueNonIntrusive ( )

inline

Destroys the MPSCQueueNonIntrusive object.

Dequeues all items and deletes them, followed by proper cleanup of remaining nodes in the queue.

        {
            T* output;
            while (Dequeue(output))
                delete output;
 
            // Properly delete remaining nodes
            Node* front = _head.load(std::memory_order_acquire);
            while (front)
            {
                Node* next = front->Next.load(std::memory_order_acquire);
                delete front;
                front = next;
            }
        }

References Acore::Impl::MPSCQueueNonIntrusive< T >::_head, Acore::Impl::MPSCQueueNonIntrusive< T >::Dequeue(), and Acore::Impl::MPSCQueueNonIntrusive< T >::Node::Next.

MPSCQueueNonIntrusive() [2/2]

template<typename T >

Acore::Impl::MPSCQueueNonIntrusive< T >::MPSCQueueNonIntrusive ( MPSCQueueNonIntrusive< T > const &  )

privatedelete

Deleted copy constructor.

Member Function Documentation

Dequeue()

template<typename T >

bool Acore::Impl::MPSCQueueNonIntrusive< T >::Dequeue ( T *&  result )

inline

Dequeues an item from the queue.

This function removes the item at the front of the queue and returns it.

Parameters

result

Reference to a pointer where the dequeued item will be stored.

Returns

True if an item was successfully dequeued, false if the queue was empty.

        {
            Node* tail = _tail.load(std::memory_order_acquire);
            Node* next = tail->Next.load(std::memory_order_acquire);
            if (!next)
                return false;
 
            result = next->Data;
            _tail.store(next, std::memory_order_release);
            delete tail;
            return true;
        }

References Acore::Impl::MPSCQueueNonIntrusive< T >::_tail, Acore::Impl::MPSCQueueNonIntrusive< T >::Node::Data, and Acore::Impl::MPSCQueueNonIntrusive< T >::Node::Next.

Referenced by Acore::Impl::MPSCQueueNonIntrusive< T >::~MPSCQueueNonIntrusive().

Enqueue()

template<typename T >

void Acore::Impl::MPSCQueueNonIntrusive< T >::Enqueue ( T *  input )

inline

Enqueues a new item in the queue.

This function adds a new item at the head of the queue.

Parameters

input

Pointer to the item to be enqueued.

< Exchange with acquire-release semantics

        {
            Node* node = new Node(input);
            Node* prevHead = _head.exchange(node, std::memory_order_acq_rel);  
            prevHead->Next.store(node, std::memory_order_release);
        }

References Acore::Impl::MPSCQueueNonIntrusive< T >::_head, and Acore::Impl::MPSCQueueNonIntrusive< T >::Node::Next.

operator=()

template<typename T >

MPSCQueueNonIntrusive & Acore::Impl::MPSCQueueNonIntrusive< T >::operator= ( MPSCQueueNonIntrusive< T > const &  )

privatedelete

Deleted copy assignment operator.

Member Data Documentation

_head

template<typename T >

std::atomic<Node*> Acore::Impl::MPSCQueueNonIntrusive< T >::_head

private

Atomic pointer to the head node of the queue.

Referenced by Acore::Impl::MPSCQueueNonIntrusive< T >::Enqueue(), Acore::Impl::MPSCQueueNonIntrusive< T >::MPSCQueueNonIntrusive(), and Acore::Impl::MPSCQueueNonIntrusive< T >::~MPSCQueueNonIntrusive().

_tail

template<typename T >

std::atomic<Node*> Acore::Impl::MPSCQueueNonIntrusive< T >::_tail

private

Atomic pointer to the tail node of the queue.

Referenced by Acore::Impl::MPSCQueueNonIntrusive< T >::Dequeue().

---

The documentation for this class was generated from the following file:

• azerothcore-wotlk/src/common/Threading/MPSCQueue.h