Class MpscRelaxedArrayQueue<E>
- java.lang.Object
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- java.util.AbstractCollection<E>
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- java.util.AbstractQueue<E>
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- org.jctools.queues.MpscRelaxedArrayQueueL0Pad<E>
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- org.jctools.queues.MpscRelaxedArrayQueueActiveCycleIdField<E>
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- org.jctools.queues.MpscRelaxedArrayQueueMidPad<E>
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- org.jctools.queues.MpscRelaxedArrayQueueProducerLimitField<E>
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- org.jctools.queues.MpscRelaxedArrayQueueL2Pad<E>
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- org.jctools.queues.MpscRelaxedArrayQueueConsumerPositionField<E>
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- org.jctools.queues.MpscRelaxedArrayQueueL3Pad<E>
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- org.jctools.queues.MpscRelaxedArrayQueueProducerCycleClaimFields<E>
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- org.jctools.queues.MpscRelaxedArrayQueueL4Pad<E>
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- org.jctools.queues.MpscRelaxedArrayQueue<E>
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- All Implemented Interfaces:
java.lang.Iterable<E>
,java.util.Collection<E>
,java.util.Queue<E>
,MessagePassingQueue<E>
public class MpscRelaxedArrayQueue<E> extends MpscRelaxedArrayQueueL4Pad<E> implements MessagePassingQueue<E>
This class is still work in progress, please do not pick up for production use just yet.
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Nested Class Summary
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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 Modifier and Type Field Description private E[]
buffer
private int
cycleIdBitShift
private int
cycleLength
private int
cycleLengthLog2
private long
mask
Note on terminology: - position/id: overall progress indicator, not an array index or offset at which to lookup/write.private long
maxCycleId
private int
positionWithinCycleMask
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Fields inherited from class org.jctools.queues.MpscRelaxedArrayQueueL4Pad
p01, p02, p03, p04, p05, p06, p10, p11, p12, p13, p14, p15, p16, p17
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Fields inherited from class org.jctools.queues.MpscRelaxedArrayQueueProducerCycleClaimFields
producerFirstCycleClaim, producerSecondCycleClaim
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Fields inherited from class org.jctools.queues.MpscRelaxedArrayQueueL3Pad
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
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Fields inherited from class org.jctools.queues.MpscRelaxedArrayQueueConsumerPositionField
consumerPosition
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Fields inherited from interface org.jctools.queues.MessagePassingQueue
UNBOUNDED_CAPACITY
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Constructor Summary
Constructors Constructor Description MpscRelaxedArrayQueue(int capacity)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description private static int
calcElementIndexInBuffer(int positionWithinCycle, int cycleIndex, int cycleLengthLog2)
Convert [position within cycle, cycleIndex] to index in buffer.int
capacity()
void
clear()
Removes all items from the queue.private long
detectSlowRotation(long claimCycleId, long nextCycleId)
int
drain(MessagePassingQueue.Consumer<E> c)
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.int
fill(MessagePassingQueue.Supplier<E> s)
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 w, MessagePassingQueue.ExitCondition exit)
Stuff the queue with elements from the supplier forever.private boolean
fixProducerOverClaim(int activeCycleIndex, long producerCycleClaim, boolean slowProducer)
It tries to fix a producer overclaim.boolean
isEmpty()
This method's accuracy is subject to concurrent modifications happening as the observation is carried out.private boolean
isFull(long producerPosition)
Given the nature of getAndAdd progress on producerPosition and given the potential risk for over claiming it is quite possible for this method to report a queue which is not full as full.java.util.Iterator<E>
iterator()
boolean
offer(E e)
Called from a producer thread subject to the restrictions appropriate to the implementation and according to theQueue.offer(Object)
interface.E
peek()
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.peek()
interface.private E
peekSlowPath(E[] buffer, long consumerPosition, long offset)
E
poll()
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.poll()
interface.private E
pollSlowPath(E[] buffer, long offset, long consumerPosition)
private static int
positionWithinCycle(long producerCycleClaim, int positionOnCycleMask)
private static long
producerClaimCycleId(long producerCycleClaim, int cycleIdBitShift)
private static long
producerPosition(int positionWithinCycle, long cycleId, int cycleLengthLog2)
Convert position in cycle and cycleId into a producer position (monotonically increasing reflection of offers that is comparable with the consumerPosition to determine size/empty/full)private static long
producerPositionFromClaim(long producerCycleClaim, int positionOnCycleMask, int cycleIdBitShift, int cycleLengthLog2)
boolean
relaxedOffer(E e)
Called from a producer thread subject to the restrictions appropriate to the implementation.E
relaxedPeek()
Called from the consumer thread subject to the restrictions appropriate to the implementation.E
relaxedPoll()
Called from the consumer thread subject to the restrictions appropriate to the implementation.private void
rotateCycle(long claimCycleId, int cycleIdBitShift, long maxCycleId)
private void
signalConsumerProgress(long consumerPosition, E[] buffer, long offset)
int
size()
This method's accuracy is subject to concurrent modifications happening as the size is estimated and as such is a best effort rather than absolute value.private void
soCycleElement(E[] buffer, E e, int activeCycleIndex, int positionWithinCycle, int cycleLengthLog2)
private E
spinForElement(E[] buffer, long offset)
java.lang.String
toString()
private boolean
validateProducerClaim(int activeCycleIndex, long producerCycleClaim, long cycleId, int positionOnCycle, int cycleLengthLog2, boolean slowProducer)
Validate a producer claim to find out if is an overclaim (beyond the producer limit).private void
validateSlowProducerOverClaim(int activeCycleIndex, long producerCycleClaim)
Validates a slow producer over-claim throwingIllegalStateException
if the offer on it can't continue.-
Methods inherited from class org.jctools.queues.MpscRelaxedArrayQueueProducerCycleClaimFields
casProducerCycleClaim, getAndIncrementProducerCycleClaim, lvProducerCycleClaim, soProducerCycleClaim
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Methods inherited from class org.jctools.queues.MpscRelaxedArrayQueueConsumerPositionField
lpConsumerPosition, lvConsumerPosition, soConsumerPosition
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Methods inherited from class org.jctools.queues.MpscRelaxedArrayQueueProducerLimitField
lvProducerLimit, soProducerLimit
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Methods inherited from class org.jctools.queues.MpscRelaxedArrayQueueActiveCycleIdField
activeCycleIndex, casActiveCycleId, lvActiveCycleId, soActiveCycleId
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Methods inherited from class java.util.AbstractCollection
contains, containsAll, remove, removeAll, retainAll, toArray, toArray
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Field Detail
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mask
private final long mask
Note on terminology: - position/id: overall progress indicator, not an array index or offset at which to lookup/write. - index: for looking up within an array (including the inlined producerCycleClaim array) - offset: for pointer like access using Unsafe The producer in this queue operates on cycleId and the producerCycleClaim array: - The cycleId grow monotonically, and the parity bit (cycleIndex) indicated which claim to use - The producerCycleClaim indicate position in a cycle as well as the originating cycleId. From a claim we can calculate the producer overall position as well as the position within a cycle. The buffer is split into 2 cycles (matching cycleIndex 0 and 1), allowing the above indicators to control producer progress on separate counters while maintaining the appearance of a contiguous buffer to the consumer.
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cycleLength
private final int cycleLength
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cycleLengthLog2
private final int cycleLengthLog2
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buffer
private final E[] buffer
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positionWithinCycleMask
private final int positionWithinCycleMask
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cycleIdBitShift
private final int cycleIdBitShift
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maxCycleId
private final long maxCycleId
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Method Detail
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iterator
public java.util.Iterator<E> iterator()
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offer
public boolean offer(E e)
Description copied from interface:MessagePassingQueue
Called from a producer thread subject to the restrictions appropriate to the implementation and according to theQueue.offer(Object)
interface.- Specified by:
offer
in interfaceMessagePassingQueue<E>
- Specified by:
offer
in interfacejava.util.Queue<E>
- Parameters:
e
- notnull
, will throw NPE if it is- Returns:
- true if element was inserted into the queue, false iff full
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isFull
private boolean isFull(long producerPosition)
Given the nature of getAndAdd progress on producerPosition and given the potential risk for over claiming it is quite possible for this method to report a queue which is not full as full.
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rotateCycle
private void rotateCycle(long claimCycleId, int cycleIdBitShift, long maxCycleId)
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detectSlowRotation
private long detectSlowRotation(long claimCycleId, long nextCycleId)
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validateProducerClaim
private boolean validateProducerClaim(int activeCycleIndex, long producerCycleClaim, long cycleId, int positionOnCycle, int cycleLengthLog2, boolean slowProducer)
Validate a producer claim to find out if is an overclaim (beyond the producer limit).- Returns:
true
if the claim is valid,false
otherwise.
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fixProducerOverClaim
private boolean fixProducerOverClaim(int activeCycleIndex, long producerCycleClaim, boolean slowProducer)
It tries to fix a producer overclaim.- Returns:
true
if the claim is now safe to be used,false
otherwise and is needed to retry the claim.
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validateSlowProducerOverClaim
private void validateSlowProducerOverClaim(int activeCycleIndex, long producerCycleClaim)
Validates a slow producer over-claim throwingIllegalStateException
if the offer on it can't continue.
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soCycleElement
private void soCycleElement(E[] buffer, E e, int activeCycleIndex, int positionWithinCycle, int cycleLengthLog2)
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poll
public E poll()
Description copied from interface:MessagePassingQueue
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.poll()
interface.- Specified by:
poll
in interfaceMessagePassingQueue<E>
- Specified by:
poll
in interfacejava.util.Queue<E>
- Returns:
- a message from the queue if one is available,
null
iff empty
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signalConsumerProgress
private void signalConsumerProgress(long consumerPosition, E[] buffer, long offset)
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peek
public E peek()
Description copied from interface:MessagePassingQueue
Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theQueue.peek()
interface.- Specified by:
peek
in interfaceMessagePassingQueue<E>
- Specified by:
peek
in interfacejava.util.Queue<E>
- Returns:
- a message from the queue if one is available,
null
iff empty
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size
public int size()
Description copied from interface:MessagePassingQueue
This method's accuracy is subject to concurrent modifications happening as the size is estimated and as such is a best effort rather than absolute value. For some implementations this method may be O(n) rather than O(1).- Specified by:
size
in interfacejava.util.Collection<E>
- Specified by:
size
in interfaceMessagePassingQueue<E>
- Specified by:
size
in classjava.util.AbstractCollection<E>
- Returns:
- number of messages in the queue, between 0 and
Integer.MAX_VALUE
but less or equals to capacity (if bounded).
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clear
public void clear()
Description copied from interface:MessagePassingQueue
Removes all items from the queue. Called from the consumer thread subject to the restrictions appropriate to the implementation and according to theCollection.clear()
interface.- Specified by:
clear
in interfacejava.util.Collection<E>
- Specified by:
clear
in interfaceMessagePassingQueue<E>
- Overrides:
clear
in classjava.util.AbstractQueue<E>
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isEmpty
public boolean isEmpty()
Description copied from interface:MessagePassingQueue
This method's accuracy is subject to concurrent modifications happening as the observation is carried out.- Specified by:
isEmpty
in interfacejava.util.Collection<E>
- Specified by:
isEmpty
in interfaceMessagePassingQueue<E>
- Overrides:
isEmpty
in classjava.util.AbstractCollection<E>
- Returns:
- true if empty, false otherwise
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capacity
public int capacity()
- Specified by:
capacity
in interfaceMessagePassingQueue<E>
- Returns:
- the capacity of this queue or
MessagePassingQueue.UNBOUNDED_CAPACITY
if not bounded
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relaxedOffer
public boolean relaxedOffer(E e)
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.- Specified by:
relaxedOffer
in interfaceMessagePassingQueue<E>
- 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
public E 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.- Specified by:
relaxedPoll
in interfaceMessagePassingQueue<E>
- Returns:
- a message from the queue if one is available,
null
if unable to poll
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relaxedPeek
public E 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.- Specified by:
relaxedPeek
in interfaceMessagePassingQueue<E>
- Returns:
- a message from the queue if one is available,
null
if unable to peek
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drain
public int drain(MessagePassingQueue.Consumer<E> c)
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.- Specified by:
drain
in interfaceMessagePassingQueue<E>
- Returns:
- the number of polled elements
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fill
public int fill(MessagePassingQueue.Supplier<E> s)
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.- Specified by:
fill
in interfaceMessagePassingQueue<E>
- Returns:
- the number of offered elements
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drain
public int drain(MessagePassingQueue.Consumer<E> c, int limit)
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.- Specified by:
drain
in interfaceMessagePassingQueue<E>
- Returns:
- the number of polled elements
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fill
public int fill(MessagePassingQueue.Supplier<E> s, int limit)
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.- Specified by:
fill
in interfaceMessagePassingQueue<E>
- 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.- Specified by:
drain
in interfaceMessagePassingQueue<E>
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fill
public void fill(MessagePassingQueue.Supplier<E> s, MessagePassingQueue.WaitStrategy w, 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.- Specified by:
fill
in interfaceMessagePassingQueue<E>
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positionWithinCycle
private static int positionWithinCycle(long producerCycleClaim, int positionOnCycleMask)
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producerClaimCycleId
private static long producerClaimCycleId(long producerCycleClaim, int cycleIdBitShift)
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producerPositionFromClaim
private static long producerPositionFromClaim(long producerCycleClaim, int positionOnCycleMask, int cycleIdBitShift, int cycleLengthLog2)
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producerPosition
private static long producerPosition(int positionWithinCycle, long cycleId, int cycleLengthLog2)
Convert position in cycle and cycleId into a producer position (monotonically increasing reflection of offers that is comparable with the consumerPosition to determine size/empty/full)
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calcElementIndexInBuffer
private static int calcElementIndexInBuffer(int positionWithinCycle, int cycleIndex, int cycleLengthLog2)
Convert [position within cycle, cycleIndex] to index in buffer.
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.util.AbstractCollection<E>
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