Class DeferredScalarSubscription<T>

java.lang.Object
java.lang.Number
java.util.concurrent.atomic.AtomicInteger
io.reactivex.rxjava3.internal.subscriptions.BasicIntQueueSubscription<T>
io.reactivex.rxjava3.internal.subscriptions.DeferredScalarSubscription<T>
Type Parameters:
T - the value type
All Implemented Interfaces:
QueueFuseable<T>, QueueSubscription<T>, SimpleQueue<T>, Serializable, org.reactivestreams.Subscription
Direct Known Subclasses:
DeferredScalarSubscriber
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

    • 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.

  • 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