Class DeferredScalarSubscription<T>

Type Parameters:
T - the value type
All Implemented Interfaces:
QueueFuseable<T>, QueueSubscription<T>, SimpleQueue<T>, Serializable, org.reactivestreams.Subscription
Direct Known Subclasses:
AsyncProcessor.AsyncSubscription, DeferredScalarSubscriber, FlowableAll.AllSubscriber, FlowableAny.AnySubscriber, FlowableCollect.CollectSubscriber, FlowableCollectWithCollector.CollectorSubscriber, FlowableCount.CountSubscriber, FlowableElementAt.ElementAtSubscriber, FlowableFromCompletionStage.CompletionStageHandler, FlowableReduce.ReduceSubscriber, FlowableSequenceEqual.EqualCoordinator, FlowableSingle.SingleElementSubscriber, FlowableTakeLastOne.TakeLastOneSubscriber, FlowableToList.ToListSubscriber, MaybeToFlowable.MaybeToFlowableSubscriber, ParallelCollector.ParallelCollectorSubscriber, ParallelReduceFull.ParallelReduceFullMainSubscriber, SingleToFlowable.SingleToFlowableObserver

public class DeferredScalarSubscription<@NonNull T> extends BasicIntQueueSubscription<T>
A subscription that signals a single value eventually.

Note that the class leaks all methods of AtomicLong. Use complete(Object) to signal the single value.

The this atomic integer stores a bit field:
bit 0: indicates that there is a value available
bit 1: indicates that there was a request made
bit 2: indicates there was a cancellation, exclusively set
bit 3: indicates in fusion mode but no value yet, exclusively set
bit 4: indicates in fusion mode and value is available, exclusively set
bit 5: indicates in fusion mode and value has been consumed, exclusively set
Where exclusively set means any other bits are 0 when that bit is set.

See Also:
  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      See Also:
    • downstream

      protected final org.reactivestreams.Subscriber<? super T> downstream
      The Subscriber to emit the value to.
    • value

      protected T value
      The value is stored here if there is no request yet or in fusion mode.
    • NO_REQUEST_NO_VALUE

      static final int NO_REQUEST_NO_VALUE
      Indicates this Subscription has no value and not requested yet.
      See Also:
    • NO_REQUEST_HAS_VALUE

      static final int NO_REQUEST_HAS_VALUE
      Indicates this Subscription has a value but not requested yet.
      See Also:
    • HAS_REQUEST_NO_VALUE

      static final int HAS_REQUEST_NO_VALUE
      Indicates this Subscription has been requested but there is no value yet.
      See Also:
    • HAS_REQUEST_HAS_VALUE

      static final int HAS_REQUEST_HAS_VALUE
      Indicates this Subscription has both request and value.
      See Also:
    • CANCELLED

      static final int CANCELLED
      Indicates the Subscription has been cancelled.
      See Also:
    • FUSED_EMPTY

      static final int FUSED_EMPTY
      Indicates this Subscription is in fusion mode and is currently empty.
      See Also:
    • FUSED_READY

      static final int FUSED_READY
      Indicates this Subscription is in fusion mode and has a value.
      See Also:
    • FUSED_CONSUMED

      static final int FUSED_CONSUMED
      Indicates this Subscription is in fusion mode and its value has been consumed.
      See Also:
  • Constructor Details

    • DeferredScalarSubscription

      public DeferredScalarSubscription(org.reactivestreams.Subscriber<? super @NonNull T> downstream)
      Creates a DeferredScalarSubscription by wrapping the given Subscriber.
      Parameters:
      downstream - the Subscriber to wrap, not null (not verified)
  • Method Details

    • request

      public final void request(long n)
    • complete

      public final void complete(@NonNull T v)
      Completes this subscription by indicating the given value should be emitted when the first request arrives.

      Make sure this is called exactly once.

      Parameters:
      v - the value to signal, not null (not validated)
    • requestFusion

      public final int requestFusion(int mode)
      Description copied from interface: QueueFuseable
      Request a fusion mode from the upstream.

      This should be called before onSubscribe returns.

      Calling this method multiple times or after onSubscribe finished is not allowed and may result in undefined behavior.

      Parameters:
      mode - the requested fusion mode, allowed values are QueueFuseable.SYNC, QueueFuseable.ASYNC, QueueFuseable.ANY combined with QueueFuseable.BOUNDARY (e.g., requestFusion(SYNC | BOUNDARY)).
      Returns:
      the established fusion mode: QueueFuseable.NONE, QueueFuseable.SYNC, QueueFuseable.ASYNC.
    • poll

      @Nullable public final T poll()
      Description copied from interface: SimpleQueue
      Tries to dequeue a value (non-null) or returns null if the queue is empty.

      If the producer uses SimpleQueue.offer(Object, Object) and when polling in pairs, if the first poll() returns a non-null item, the second poll() is guaranteed to return a non-null item as well.

      Returns:
      the item or null to indicate an empty queue
    • isEmpty

      public final boolean isEmpty()
      Description copied from interface: SimpleQueue
      Returns true if the queue is empty.

      Note however that due to potential fused functions in SimpleQueue.poll() it is possible this method returns false but then poll() returns null because the fused function swallowed the available item(s).

      Returns:
      true if the queue is empty
    • clear

      public final void clear()
      Description copied from interface: SimpleQueue
      Removes all enqueued items from this queue.
    • cancel

      public void cancel()
    • isCancelled

      public final boolean isCancelled()
      Returns true if this Subscription has been cancelled.
      Returns:
      true if this Subscription has been cancelled
    • tryCancel

      public final boolean tryCancel()
      Atomically sets a cancelled state and returns true if the current thread did it successfully.
      Returns:
      true if the current thread cancelled