Top Description Fields Constructors Methods
io.netty.util.internal.shaded.org.jctools.queues

public Class SpscArrayQueue<E>

Additional top-level classes in compilation unit: SpscArrayQueueColdField, SpscArrayQueueL1Pad, SpscArrayQueueProducerIndexFields, SpscArrayQueueL2Pad, SpscArrayQueueConsumerIndexField, SpscArrayQueueL3Pad.

extends SpscArrayQueueL3Pad<E>
Class Inheritance
Static Imports
io.netty.util.internal.shaded.org.jctools.util.UnsafeAccess.UNSAFE, .UnsafeAccess.fieldOffset, io.netty.util.internal.shaded.org.jctools.util.UnsafeRefArrayAccess.*
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.

Field Summary

Inherited from io.netty.util.internal.shaded.org.jctools.queues.SpscArrayQueueL3Pad:
b000b001b002b003b004b005b006b007b010b011b012b013b014b015b016b017b020b021b022b023b024b025b026b027b030b031b032b033b034b035b036b037b040b041b042b043b044b045b046b047b050b051b052b053b054b055b056b057b060b061b062b063b064b065b066b067b070b071b072b073b074b075b076b077b100b101b102b103b104b105b106b107b110b111b112b113b114b115b116b117b120b121b122b123b124b125b126b127b130b131b132b133b134b135b136b137b140b141b142b143b144b145b146b147b150b151b152b153b154b155b156b157b160b161b162b163b164b165b166b167b170b171b172b173b174b175b176b177

Constructor Summary

AccessConstructor and Description
public
SpscArrayQueue(final int capacity)

Method Summary

Modifier and TypeMethod and Description
public int
drain(final MessagePassingQueue.Consumer<E> c)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

Remove all available item from the queue and hand to consume.
public int
drain(final MessagePassingQueue.Consumer<E> c, final int limit)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

Remove up to limit elements from the queue and hand to consume.
public void
drain(final MessagePassingQueue.Consumer<E> c, final MessagePassingQueue.WaitStrategy w, final MessagePassingQueue.ExitCondition exit)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

Remove elements from the queue and hand to consume forever.
public int
fill(final MessagePassingQueue.Supplier<E> s)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

Stuff the queue with elements from the supplier.
public int
fill(final MessagePassingQueue.Supplier<E> s, final int limit)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

Stuff the queue with up to limit elements from the supplier.
public void
fill(final MessagePassingQueue.Supplier<E> s, final MessagePassingQueue.WaitStrategy w, final MessagePassingQueue.ExitCondition e)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

Stuff the queue with elements from the supplier forever.
public boolean
offer(final E
not null, will throw NPE if it is
e)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.offer, java.util.Queue.offer.

Called from a producer thread subject to the restrictions appropriate to the implementation and according to the Queue#offer(Object) interface.
private boolean
offerSlowPath(final E[] buffer, final long mask, final long producerIndex)

public E
peek()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.peek, java.util.Queue.peek.

Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue#peek() interface.
public E
poll()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.poll, java.util.Queue.poll.

Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue#poll() interface.
public boolean
relaxedOffer(final E
not null, will throw NPE if it is
message)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedOffer.

Called from a producer thread subject to the restrictions appropriate to the implementation.
public E
relaxedPeek()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedPeek.

Called from the consumer thread subject to the restrictions appropriate to the implementation.
public E
relaxedPoll()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedPoll.

Called from the consumer thread subject to the restrictions appropriate to the implementation.

Constructor Detail

SpscArrayQueueback to summary
public SpscArrayQueue(final int capacity)

Method Detail

drainback to summary
public int drain(final MessagePassingQueue.Consumer<E> c)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

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 Consumer#accept make sure you have read and understood these before using this method.

Returns:int

the number of polled elements

Annotations
@Override
drainback to summary
public int drain(final MessagePassingQueue.Consumer<E> c, final int limit)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

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 Consumer#accept make sure you have read and understood these before using this method.

Returns:int

the number of polled elements

Annotations
@Override
drainback to summary
public void drain(final MessagePassingQueue.Consumer<E> c, final MessagePassingQueue.WaitStrategy w, final MessagePassingQueue.ExitCondition exit)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.drain.

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 Consumer#accept make sure you have read and understood these before using this method.

Annotations
@Override
fillback to summary
public int fill(final MessagePassingQueue.Supplier<E> s)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

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 Supplier#get make sure you have read and understood these before using this method.

Returns:int

the number of offered elements

Annotations
@Override
fillback to summary
public int fill(final MessagePassingQueue.Supplier<E> s, final int limit)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

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 Supplier#get make sure you have read and understood these before using this method.

Returns:int

the number of offered elements

Annotations
@Override
fillback to summary
public void fill(final MessagePassingQueue.Supplier<E> s, final MessagePassingQueue.WaitStrategy w, final MessagePassingQueue.ExitCondition e)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.fill.

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 Supplier#get

Warning

Explicit assumptions are made with regards to Supplier#get make sure you have read and understood these before using this method.

Annotations
@Override
offerback to summary
public boolean offer(final E e)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.offer, java.util.Queue.offer.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.offer.

Called from a producer thread subject to the restrictions appropriate to the implementation and according to the Queue#offer(Object) interface.

This implementation is correct for single producer thread use only.

Parameters
e:E

not null, will throw NPE if it is

Returns:boolean

true if element was inserted into the queue, false iff full

Annotations
@Override
offerSlowPathback to summary
private boolean offerSlowPath(final E[] buffer, final long mask, final long producerIndex)
peekback to summary
public E peek()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.peek, java.util.Queue.peek.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.peek.

Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue#peek() interface.

This implementation is correct for single consumer thread use only.

Returns:E

a message from the queue if one is available, null iff empty

Annotations
@Override
pollback to summary
public E poll()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.poll, java.util.Queue.poll.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.poll.

Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue#poll() interface.

This implementation is correct for single consumer thread use only.

Returns:E

a message from the queue if one is available, null iff empty

Annotations
@Override
relaxedOfferback to summary
public boolean relaxedOffer(final E message)

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedOffer.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedOffer.

Called from a producer thread subject to the restrictions appropriate to the implementation. As opposed to Queue#offer(Object) this method may return false without the queue being full.

Parameters
message:E

not null, will throw NPE if it is

Returns:boolean

true if element was inserted into the queue, false if unable to offer

Annotations
@Override
relaxedPeekback to summary
public E relaxedPeek()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedPeek.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedPeek.

Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed to Queue#peek() this method may return null without the queue being empty.

Returns:E

a message from the queue if one is available, null if unable to peek

Annotations
@Override
relaxedPollback to summary
public E relaxedPoll()

Implements io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedPoll.

Doc from io.netty.util.internal.shaded.org.jctools.queues.MessagePassingQueue.relaxedPoll.

Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed to Queue#poll() this method may return null without the queue being empty.

Returns:E

a message from the queue if one is available, null if unable to poll

Annotations
@Override