Class ScalarSubscription<T>

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

public final class ScalarSubscription<T> extends AtomicInteger implements QueueSubscription<T>
A Subscription that holds a constant value and emits it only when requested.
See Also:
  • Field Details

    • serialVersionUID

      private static final long serialVersionUID
      See Also:
    • value

      final T value
      The single value to emit, set to null.
    • subscriber

      final org.reactivestreams.Subscriber<? super T> subscriber
      The actual subscriber.
    • NO_REQUEST

      static final int NO_REQUEST
      No request has been issued yet.
      See Also:
    • REQUESTED

      static final int REQUESTED
      Request has been called.
      See Also:
    • CANCELLED

      static final int CANCELLED
      Cancel has been called.
      See Also:
  • Constructor Details

    • ScalarSubscription

      public ScalarSubscription(org.reactivestreams.Subscriber<? super T> subscriber, T value)
  • Method Details

    • request

      public void request(long n)
      Specified by:
      request in interface org.reactivestreams.Subscription
    • cancel

      public void cancel()
      Specified by:
      cancel in interface org.reactivestreams.Subscription
    • isCancelled

      public boolean isCancelled()
      Returns true if this Subscription was cancelled.
      Returns:
      true if this Subscription was cancelled
    • offer

      public boolean offer(T e)
      Description copied from interface: SimpleQueue
      Atomically enqueue a single value.
      Specified by:
      offer in interface SimpleQueue<T>
      Parameters:
      e - the value to enqueue, not null
      Returns:
      true if successful, false if the value was not enqueued likely due to reaching the queue capacity)
    • offer

      public boolean offer(T v1, T v2)
      Description copied from interface: SimpleQueue
      Atomically enqueue two values.
      Specified by:
      offer in interface SimpleQueue<T>
      Parameters:
      v1 - the first value to enqueue, not null
      v2 - the second value to enqueue, not null
      Returns:
      true if successful, false if the value was not enqueued likely due to reaching the queue capacity)
    • poll

      @Nullable public 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.

      Specified by:
      poll in interface SimpleQueue<T>
      Returns:
      the item or null to indicate an empty queue
    • isEmpty

      public 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).

      Specified by:
      isEmpty in interface SimpleQueue<T>
      Returns:
      true if the queue is empty
    • clear

      public void clear()
      Description copied from interface: SimpleQueue
      Removes all enqueued items from this queue.
      Specified by:
      clear in interface SimpleQueue<T>
    • requestFusion

      public 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.

      Specified by:
      requestFusion in interface QueueFuseable<T>
      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.