org.jctools.queues

Class SpscArrayQueue<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

org.jctools.queues.ConcurrentCircularArrayQueue<E>

org.jctools.queues.SpscArrayQueue<E>

Type Parameters:

E -

All Implemented Interfaces:

Iterable<E>, Collection<E>, Queue<E>

public final class SpscArrayQueue<E>
extends ConcurrentCircularArrayQueue<E>

A Single-Producer-Single-Consumer queue backed by a pre-allocated buffer.

This implementation is a mashup of the Fast Flow algorithm with an optimization of the offer method taken from the BQueue algorithm (a variation on Fast Flow), and adjusted to comply with Queue.offer semantics with regards to capacity.
For convenience the relevant papers are available in the resources folder:
2010 - Pisa - SPSC Queues on Shared Cache Multi-Core Systems.pdf
2012 - Junchang- BQueue- Efficient and Practical Queuing.pdf
This implementation is wait free.

Author:

nitsanw

Field Summary

Fields

Modifier and Type	Field and Description
protected long	consumerIndex
protected int	lookAheadStep
protected long	producerIndex
protected long	producerLookAhead

Fields inherited from class org.jctools.queues.ConcurrentCircularArrayQueue

buffer, BUFFER_PAD, capacity, mask, SPARSE_SHIFT

Constructor Summary

Constructors

Constructor and Description
SpscArrayQueue(int capacity)

Method Summary

Modifier and Type	Method and Description
boolean	isEmpty() This method's accuracy is subject to concurrent modifications happening as the observation is carried out.
protected long	lvConsumerIndex()
protected long	lvProducerIndex()
boolean	offer(E e)
E	peek()
E	poll()
int	size()

Methods inherited from class org.jctools.queues.ConcurrentCircularArrayQueue

calcElementOffset, clear, iterator, lpElement, lpElement, lvElement, lvElement, soElement, soElement, spElement, spElement

Methods inherited from class java.util.AbstractQueue

add, addAll, element, remove

Methods inherited from class java.util.AbstractCollection

contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

contains, containsAll, equals, hashCode, isEmpty, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray

Methods inherited from interface java.lang.Iterable

forEach

Field Detail

consumerIndex

protected long consumerIndex

producerIndex

protected long producerIndex

producerLookAhead

protected long producerLookAhead

lookAheadStep

protected final int lookAheadStep

Constructor Detail

SpscArrayQueue

public SpscArrayQueue(int capacity)

Method Detail

offer

public boolean offer(E e)

This implementation is correct for single producer thread use only.

poll

public E poll()

This implementation is correct for single consumer thread use only.

peek

public E peek()

This implementation is correct for single consumer thread use only.

size

public int size()

Specified by:

size in interface Collection<E>

Specified by:

size in class AbstractCollection<E>

lvConsumerIndex

protected final long lvConsumerIndex()

lvProducerIndex

protected final long lvProducerIndex()

isEmpty

public boolean isEmpty()

This method's accuracy is subject to concurrent modifications happening as the observation is carried out.

Returns:

true if empty, false otherwise