io.smallrye.mutiny.helpers.queues

Class MpscLinkedQueue<T>

java.lang.Object

io.smallrye.mutiny.helpers.queues.MpscLinkedQueue<T>

Type Parameters:

T - the contained value type

All Implemented Interfaces:

Iterable<T>, Collection<T>, Queue<T>

public final class MpscLinkedQueue<T>
extends Object
implements Queue<T>

A multi-producer single consumer unbounded queue. Code from RX Java 2.

Constructor Summary

Constructors

Constructor and Description
MpscLinkedQueue()

Method Summary

Modifier and Type	Method and Description
boolean	add(T t)
boolean	addAll(Collection<? extends T> c)
void	clear()
boolean	contains(Object o)
boolean	containsAll(Collection<?> c)
T	element()
boolean	isEmpty()
Iterator<T>	iterator()
boolean	offer(T e)
T	peek()
T	poll()
T	remove()
boolean	remove(Object o)
boolean	removeAll(Collection<?> c)
boolean	retainAll(Collection<?> c)
int	size()
Object[]	toArray()
<T1> T1[]	toArray(T1[] a)

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Collection

equals, hashCode, parallelStream, removeIf, spliterator, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

MpscLinkedQueue

public MpscLinkedQueue()

Method Detail

add

public boolean add(T t)

Specified by:

add in interface Collection<T>

Specified by:

add in interface Queue<T>

remove

public boolean remove(Object o)

Specified by:

remove in interface Collection<T>

containsAll

public boolean containsAll(Collection<?> c)

Specified by:

containsAll in interface Collection<T>

addAll

public boolean addAll(Collection<? extends T> c)

Specified by:

addAll in interface Collection<T>

removeAll

public boolean removeAll(Collection<?> c)

Specified by:

removeAll in interface Collection<T>

retainAll

public boolean retainAll(Collection<?> c)

Specified by:

retainAll in interface Collection<T>

offer

public boolean offer(T e)

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.

Specified by:

offer in interface Queue<T>

See Also:

Queue.offer(Object)

remove

public T remove()

Specified by:

remove in interface Queue<T>

poll

public T 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.

Specified by:

poll in interface Queue<T>

See Also:

Queue.poll()

element

public T element()

Specified by:

element in interface Queue<T>

peek

public T peek()

Specified by:

peek in interface Queue<T>

clear

public void clear()

Specified by:

clear in interface Collection<T>

size

public int size()

Specified by:

size in interface Collection<T>

isEmpty

public 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<T>

contains

public boolean contains(Object o)

Specified by:

contains in interface Collection<T>

iterator

public Iterator<T> iterator()

Specified by:

iterator in interface Iterable<T>

Specified by:

iterator in interface Collection<T>

toArray

public Object[] toArray()

Specified by:

toArray in interface Collection<T>

toArray

public <T1> T1[] toArray(T1[] a)

Specified by:

toArray in interface Collection<T>