Class MpscArrayQueue<E>
- All Implemented Interfaces:
Iterable<E>
,Collection<E>
,Queue<E>
,IndexedQueueSizeUtil.IndexedQueue
,MessagePassingQueue<E>
,QueueProgressIndicators
,SupportsIterator
ConcurrentCircularArrayQueue
. This
implies that any thread may call the offer method, but only a single thread may call poll/peek for correctness to
maintained. This implementation follows patterns documented on the package level for False Sharing protection.
This implementation is using the Fast Flow method for polling from the queue (with minor change to correctly publish the index) and an extension of the Leslie Lamport concurrent queue algorithm (originated by Martin Thompson) on the producer side.
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Nested Class Summary
Nested classes/interfaces inherited from interface org.jctools.queues.MessagePassingQueue
MessagePassingQueue.Consumer<T>, MessagePassingQueue.ExitCondition, MessagePassingQueue.Supplier<T>, MessagePassingQueue.WaitStrategy
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Field Summary
Fields inherited from class org.jctools.queues.MpscArrayQueueL3Pad
b000, b001, b002, b003, b004, b005, b006, b007, b010, b011, b012, b013, b014, b015, b016, b017, b020, b021, b022, b023, b024, b025, b026, b027, b030, b031, b032, b033, b034, b035, b036, b037, b040, b041, b042, b043, b044, b045, b046, b047, b050, b051, b052, b053, b054, b055, b056, b057, b060, b061, b062, b063, b064, b065, b066, b067, b070, b071, b072, b073, b074, b075, b076, b077, b100, b101, b102, b103, b104, b105, b106, b107, b110, b111, b112, b113, b114, b115, b116, b117, b120, b121, b122, b123, b124, b125, b126, b127, b130, b131, b132, b133, b134, b135, b136, b137, b140, b141, b142, b143, b144, b145, b146, b147, b150, b151, b152, b153, b154, b155, b156, b157, b160, b161, b162, b163, b164, b165, b166, b167, b170, b171, b172, b173, b174, b175, b176, b177
Fields inherited from class org.jctools.queues.ConcurrentCircularArrayQueue
buffer, mask
Fields inherited from interface org.jctools.queues.MessagePassingQueue
UNBOUNDED_CAPACITY
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionint
Remove all available item from the queue and hand to consume.int
drain
(MessagePassingQueue.Consumer<E> c, int limit) Remove up to limit elements from the queue and hand to consume.void
drain
(MessagePassingQueue.Consumer<E> c, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition exit) Remove elements from the queue and hand to consume forever.final int
failFastOffer
(E e) A wait free alternative to offer which fails on CAS failure.int
Stuff the queue with elements from the supplier.int
fill
(MessagePassingQueue.Supplier<E> s, int limit) Stuff the queue with up to limit elements from the supplier.void
fill
(MessagePassingQueue.Supplier<E> s, MessagePassingQueue.WaitStrategy wait, MessagePassingQueue.ExitCondition exit) Stuff the queue with elements from the supplier forever.boolean
Called from a producer thread subject to the restrictions appropriate to the implementation and according to theQueue.offer(Object)
interface.boolean
offerIfBelowThreshold
(E e, int threshold) offer(E)
} ifConcurrentCircularArrayQueue.size()
is less than threshold.peek()
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.peek()
interface.poll()
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.poll()
interface.boolean
relaxedOffer
(E e) Called from a producer thread subject to the restrictions appropriate to the implementation.Called from the consumer thread subject to the restrictions appropriate to the implementation.Called from the consumer thread subject to the restrictions appropriate to the implementation.Methods inherited from class org.jctools.queues.MpscArrayQueueConsumerIndexField
lpConsumerIndex, lvConsumerIndex, soConsumerIndex
Methods inherited from class org.jctools.queues.MpscArrayQueueProducerLimitField
lvProducerLimit, soProducerLimit
Methods inherited from class org.jctools.queues.MpscArrayQueueProducerIndexField
casProducerIndex, lvProducerIndex
Methods inherited from class org.jctools.queues.ConcurrentCircularArrayQueue
capacity, clear, currentConsumerIndex, currentProducerIndex, isEmpty, iterator, size, toString
Methods inherited from class java.util.AbstractQueue
add, addAll, element, remove
Methods inherited from class java.util.AbstractCollection
contains, containsAll, remove, removeAll, retainAll, toArray, toArray
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, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray, toArray
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Constructor Details
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MpscArrayQueue
public MpscArrayQueue(int capacity)
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Method Details
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offerIfBelowThreshold
offer(E)
} ifConcurrentCircularArrayQueue.size()
is less than threshold.- Parameters:
e
- the object to offer onto the queue, not nullthreshold
- the maximum allowable size- Returns:
- true if the offer is successful, false if queue size exceeds threshold
- Since:
- 1.0.1
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offer
Called from a producer thread subject to the restrictions appropriate to the implementation and according to theQueue.offer(Object)
interface.
IMPLEMENTATION NOTES:
Lock free offer using a single CAS. As class name suggests access is permitted to many threads concurrently.- Parameters:
e
- notnull
, will throw NPE if it is- Returns:
- true if element was inserted into the queue, false iff full
- See Also:
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failFastOffer
A wait free alternative to offer which fails on CAS failure.- Parameters:
e
- new element, not null- Returns:
- 1 if next element cannot be filled, -1 if CAS failed, 0 if successful
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poll
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.poll()
interface.IMPLEMENTATION NOTES:
Lock free poll using ordered loads/stores. As class name suggests access is limited to a single thread.- Returns:
- a message from the queue if one is available,
null
iff empty - See Also:
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peek
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.peek()
interface.IMPLEMENTATION NOTES:
Lock free peek using ordered loads. As class name suggests access is limited to a single thread.- Returns:
- a message from the queue if one is available,
null
iff empty - See Also:
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relaxedOffer
Description copied from interface:MessagePassingQueue
Called from a producer thread subject to the restrictions appropriate to the implementation. As opposed toQueue.offer(Object)
this method may return false without the queue being full.- Parameters:
e
- notnull
, will throw NPE if it is- Returns:
- true if element was inserted into the queue, false if unable to offer
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relaxedPoll
Description copied from interface:MessagePassingQueue
Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed toQueue.poll()
this method may returnnull
without the queue being empty.- Returns:
- a message from the queue if one is available,
null
if unable to poll
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relaxedPeek
Description copied from interface:MessagePassingQueue
Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed toQueue.peek()
this method may returnnull
without the queue being empty.- Returns:
- a message from the queue if one is available,
null
if unable to peek
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drain
Description copied from interface:MessagePassingQueue
Remove up to limit elements from the queue and hand to consume. This should be semantically similar to:M m; int i = 0; for(;i < limit && (m = relaxedPoll()) != null; i++){ c.accept(m); } return i;
There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.
WARNING: Explicit assumptions are made with regards to
MessagePassingQueue.Consumer.accept(T)
make sure you have read and understood these before using this method.- Returns:
- the number of polled elements
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fill
Description copied from interface:MessagePassingQueue
Stuff the queue with up to limit elements from the supplier. Semantically similar to:for(int i=0; i < limit && relaxedOffer(s.get()); i++);
There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation. WARNING: Explicit assumptions are made with regards to
MessagePassingQueue.Supplier.get()
make sure you have read and understood these before using this method.- Returns:
- the number of offered elements
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drain
Description copied from interface:MessagePassingQueue
Remove all available item from the queue and hand to consume. This should be semantically similar to:M m; while((m = relaxedPoll()) != null){ c.accept(m); }
There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.WARNING: Explicit assumptions are made with regards to
MessagePassingQueue.Consumer.accept(T)
make sure you have read and understood these before using this method.- Returns:
- the number of polled elements
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fill
Description copied from interface:MessagePassingQueue
Stuff the queue with elements from the supplier. Semantically similar to:while(relaxedOffer(s.get());
There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation.Unbounded queues will fill up the queue with a fixed amount rather than fill up to oblivion. WARNING: Explicit assumptions are made with regards to
MessagePassingQueue.Supplier.get()
make sure you have read and understood these before using this method.- Returns:
- the number of offered elements
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drain
public void drain(MessagePassingQueue.Consumer<E> c, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition exit) Description copied from interface:MessagePassingQueue
Remove elements from the queue and hand to consume forever. Semantically similar to:int idleCounter = 0; while (exit.keepRunning()) { E e = relaxedPoll(); if(e==null){ idleCounter = wait.idle(idleCounter); continue; } idleCounter = 0; c.accept(e); }
Called from a consumer thread subject to the restrictions appropriate to the implementation.
WARNING: Explicit assumptions are made with regards to
MessagePassingQueue.Consumer.accept(T)
make sure you have read and understood these before using this method. -
fill
public void fill(MessagePassingQueue.Supplier<E> s, MessagePassingQueue.WaitStrategy wait, MessagePassingQueue.ExitCondition exit) Description copied from interface:MessagePassingQueue
Stuff the queue with elements from the supplier forever. Semantically similar to:int idleCounter = 0; while (exit.keepRunning()) { E e = s.get(); while (!relaxedOffer(e)) { idleCounter = wait.idle(idleCounter); continue; } idleCounter = 0; }
Called from a producer thread subject to the restrictions appropriate to the implementation. The main difference being that implementors MUST assure room in the queue is available BEFORE calling
MessagePassingQueue.Supplier.get()
. WARNING: Explicit assumptions are made with regards toMessagePassingQueue.Supplier.get()
make sure you have read and understood these before using this method.
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