Field Detail

• C_NODE_OFFSET

  protected static final long C_NODE_OFFSET

• consumerNode

  protected LinkedQueueNode<E> consumerNode

• P_NODE_OFFSET

  protected static final long P_NODE_OFFSET

• producerNode

  protected LinkedQueueNode<E> producerNode

Constructor Detail

• MpscLinkedQueue

  public MpscLinkedQueue()

Method Detail

• xchgProducerNode

  protected final LinkedQueueNode<E> xchgProducerNode(LinkedQueueNode<E> newVal)

• offer

  public final boolean offer(E nextValue)

  
  

  IMPLEMENTATION NOTES:
  Offer is allowed from multiple threads.
  Offer allocates a new node and:

  1. Swaps it atomically with current producer node (only one producer 'wins')
  2. Sets the new node as the node following from the swapped producer node

  This works because each producer is guaranteed to 'plant' a new node and link the old node. No 2 producers can get the same producer node as part of XCHG guarantee.

  See Also:

  MessagePassingQueue.offer(Object), Queue.offer(java.lang.Object)

• poll

  public final E poll()

  
  

  IMPLEMENTATION NOTES:
  Poll is allowed from a SINGLE thread.
  Poll reads the next node from the consumerNode and:

  1. If it is null, the queue is assumed empty (though it might not be).
  2. If it is not null set it as the consumer node and return it's now evacuated value.

  This means the consumerNode.value is always null, which is also the starting point for the queue. Because null values are not allowed to be offered this is the only node with it's value set to null at any one time.

  See Also:

  MessagePassingQueue.poll(), Queue.poll()

• peek

  public final E peek()

• iterator

  public final Iterator<E> iterator()

• size

  public final int size()

  
  

  IMPLEMENTATION NOTES:
  This is an O(n) operation as we run through all the nodes and count them.
  

  Specified by:

  size in interface  Collection<E>

  Specified by:

  size in class  AbstractCollection<E>

  See Also:

  Collection.size()

• isEmpty

  public final boolean isEmpty()

  
  

  IMPLEMENTATION NOTES:
  Queue is empty when producerNode is the same as consumerNode. An alternative implementation would be to observe the producerNode.value is null, which also means an empty queue because only the consumerNode.value is allowed to be null.

  Specified by:

  isEmpty in interface  Collection<E>

  Overrides:

  isEmpty in class  AbstractCollection<E>

  See Also:

  MessagePassingQueue.isEmpty()

• spConsumerNode

  protected final void spConsumerNode(LinkedQueueNode<E> node)

• lvConsumerNode

  protected final LinkedQueueNode<E> lvConsumerNode()

• lpConsumerNode

  protected final LinkedQueueNode<E> lpConsumerNode()

• spProducerNode

  protected final void spProducerNode(LinkedQueueNode<E> node)

• lvProducerNode

  protected final LinkedQueueNode<E> lvProducerNode()

• lpProducerNode

  protected final LinkedQueueNode<E> lpProducerNode()