public class SpscUnpaddedArrayQueue<E> extends AbstractQueue<E>
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.
MessagePassingQueue.Consumer<T>, MessagePassingQueue.ExitCondition, MessagePassingQueue.Supplier<T>, MessagePassingQueue.WaitStrategy| Modifier and Type | Field and Description |
|---|---|
protected E[] |
buffer |
protected long |
mask |
protected long |
producerLimit |
UNBOUNDED_CAPACITY| Constructor and Description |
|---|
SpscUnpaddedArrayQueue(int capacity) |
| Modifier and Type | Method and Description |
|---|---|
int |
capacity() |
void |
clear()
Removes all items from the queue.
|
long |
currentConsumerIndex()
This method has no concurrent visibility semantics.
|
long |
currentProducerIndex()
This method has no concurrent visibility semantics.
|
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 e)
Stuff the queue with elements from the supplier forever.
|
boolean |
isEmpty()
This method's accuracy is subject to concurrent modifications happening as the observation is carried
out.
|
Iterator<E> |
iterator()
Get an iterator for this queue.
|
long |
lvConsumerIndex() |
long |
lvProducerIndex() |
boolean |
offer(E e)
Called from a producer thread subject to the restrictions appropriate to the implementation and
according to the
Queue.offer(Object) interface. |
E |
peek()
Called from the consumer thread subject to the restrictions appropriate to the implementation and
according to the
Queue.peek() interface. |
E |
poll()
Called from the consumer thread subject to the restrictions appropriate to the implementation and
according to the
Queue.poll() interface. |
boolean |
relaxedOffer(E message)
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.
|
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.
|
String |
toString() |
add, addAll, element, removecontains, containsAll, remove, removeAll, retainAll, toArray, toArrayclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitcontains, containsAll, equals, hashCode, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArrayprotected long producerLimit
protected final long mask
protected final E[] buffer
public boolean offer(E e)
Queue.offer(Object) interface.
This implementation is correct for single producer thread use only.
e - not null, will throw NPE if it ispublic E poll()
Queue.poll() interface.
This implementation is correct for single consumer thread use only.
null iff emptypublic E peek()
Queue.peek() interface.
This implementation is correct for single consumer thread use only.
null iff emptypublic boolean relaxedOffer(E message)
MessagePassingQueueQueue.offer(Object) this method may return false without the queue being full.message - not null, will throw NPE if it ispublic E relaxedPoll()
MessagePassingQueueQueue.poll() this method may return null without the queue being empty.null if unable to pollpublic E relaxedPeek()
MessagePassingQueueQueue.peek() this method may return null without the queue being empty.null if unable to peekpublic int drain(MessagePassingQueue.Consumer<E> c)
MessagePassingQueue
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.
public int fill(MessagePassingQueue.Supplier<E> s)
MessagePassingQueuewhile(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.
public int drain(MessagePassingQueue.Consumer<E> c, int limit)
MessagePassingQueue
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.
public int fill(MessagePassingQueue.Supplier<E> s, int limit)
MessagePassingQueue
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.
public void drain(MessagePassingQueue.Consumer<E> c, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition exit)
MessagePassingQueue
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.
public void fill(MessagePassingQueue.Supplier<E> s, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition e)
MessagePassingQueue
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 to MessagePassingQueue.Supplier.get() make sure you have read
and understood these before using this method.
public final long lvConsumerIndex()
public final long lvProducerIndex()
public int size()
MessagePassingQueuesize in interface Collection<E>size in interface MessagePassingQueue<E>size in class AbstractCollection<E>Integer.MAX_VALUE but less or equals to
capacity (if bounded).public boolean isEmpty()
MessagePassingQueueisEmpty in interface Collection<E>isEmpty in interface MessagePassingQueue<E>isEmpty in class AbstractCollection<E>public String toString()
toString in class AbstractCollection<E>public void clear()
MessagePassingQueueCollection.clear() interface.clear in interface Collection<E>clear in interface MessagePassingQueue<E>clear in class AbstractQueue<E>public int capacity()
capacity in interface IndexedQueueSizeUtil.IndexedQueuecapacity in interface MessagePassingQueue<E>MessagePassingQueue.UNBOUNDED_CAPACITY if not boundedpublic long currentProducerIndex()
QueueProgressIndicatorscurrentProducerIndex in interface QueueProgressIndicatorspublic long currentConsumerIndex()
QueueProgressIndicatorscurrentConsumerIndex in interface QueueProgressIndicatorspublic Iterator<E> iterator()
The iterator provides a best-effort snapshot of the elements in the queue. The returned iterator is not guaranteed to return elements in queue order, and races with the consumer thread may cause gaps in the sequence of returned elements. Like {link #relaxedPoll}, the iterator may not immediately return newly inserted elements.
iterator in interface Iterable<E>iterator in interface Collection<E>iterator in class AbstractCollection<E>Copyright © 2013–2024. All rights reserved.