reactor.util.concurrent

Class MpscLinkedQueue<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

reactor.util.concurrent.MpscLinkedQueue<E>

Type Parameters:

E - the contained value type

All Implemented Interfaces:

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

public class MpscLinkedQueue<E>
extends AbstractQueue<E>
implements BiPredicate<E,E>

A multi-producer single consumer unbounded queue.

Constructor Summary

Constructors

Constructor and Description
MpscLinkedQueue()

Method Summary

Modifier and Type	Method and Description
void	clear()
boolean	isEmpty()
Iterator<E>	iterator()
boolean	offer(E e)
E	peek()
E	poll()
boolean	remove(Object o)
int	size()
boolean	test(E e1, E e2) This is an additional Queue extension for Queue.offer(E) which allows atomically offer two elements at once.

Methods inherited from class java.util.AbstractQueue

add, addAll, element, remove

Methods inherited from class java.util.AbstractCollection

contains, containsAll, 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.function.BiPredicate

and, negate, or

Methods inherited from interface java.util.Collection

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

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

MpscLinkedQueue

public MpscLinkedQueue()

Method Detail

offer

public final boolean offer(E 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<E>

See Also:

Queue.offer(java.lang.Object)

test

public boolean test(E e1,
                    E e2)

This is an additional Queue extension for Queue.offer(E) which allows atomically offer two elements at once.

IMPLEMENTATION NOTES:
Offer over test(E, E) is allowed from multiple threads.
Offer over test(E, E) allocates a two new nodes and:

1. Swaps them atomically with current producer node (only one producer 'wins')
2. Sets the new nodes 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:

test in interface BiPredicate<E,E>

Parameters:

e1 - first element to offer

e2 - second element to offer

Returns:

indicate whether elements has been successfully offered

See Also:

Queue.offer(java.lang.Object)

poll

@Nullable
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 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<E>

See Also:

Queue.poll()

peek

@Nullable
public E peek()

Specified by:

peek in interface Queue<E>

remove

public boolean remove(Object o)

Specified by:

remove in interface Collection<E>

Overrides:

remove in class AbstractCollection<E>

clear

public void clear()

Specified by:

clear in interface Collection<E>

Overrides:

clear in class AbstractQueue<E>

size

public int size()

Specified by:

size in interface Collection<E>

Specified by:

size in class AbstractCollection<E>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Collection<E>

Overrides:

isEmpty in class AbstractCollection<E>

iterator

public Iterator<E> iterator()

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in class AbstractCollection<E>