Class SpscLinkedQueue<E>

Type Parameters:
E -
All Implemented Interfaces:
Iterable<E>, Collection<E>, Queue<E>

public final class SpscLinkedQueue<E> extends BaseLinkedQueue<E>
This is a weakened version of the MPSC algorithm as presented on 1024 Cores by D. Vyukov. The original has been adapted to Java and it's quirks with regards to memory model and layout:
  1. Use inheritance to ensure no false sharing occurs between producer/consumer node reference fields.
  2. As this is an SPSC we have no need for XCHG, an ordered store is enough.
The queue is initialized with a stub node which is set to both the producer and consumer node references. From this point follow the notes on offer/poll.
  • Constructor Details

    • SpscLinkedQueue

      public SpscLinkedQueue()
  • Method Details

    • offer

      public boolean offer(E nextValue)

      IMPLEMENTATION NOTES:
      Offer is allowed from a SINGLE thread.
      Offer allocates a new node (holding the offered value) and:
      1. Sets that node as the producerNode.next
      2. Sets the new node as the producerNode
      From this follows that producerNode.next is always null and for all other nodes node.next is not null.
      See Also:
    • poll

      public 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 empty.
      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.
    • peek

      public E peek()