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:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
(package private) static final int	CANCELLED	Cancel has been called.
(package private) static final int	NO_REQUEST	No request has been issued yet.
(package private) static final int	REQUESTED	Request has been called.
private static final long	serialVersionUID
(package private) final org.reactivestreams.Subscriber<? super T>	subscriber	The actual subscriber.
(package private) final T	value	The single value to emit, set to null.

Fields inherited from interface QueueFuseable

ANY, ASYNC, BOUNDARY, NONE, SYNC

Constructor Summary

Constructors

Constructor	Description
ScalarSubscription(org.reactivestreams.Subscriber<? super T> subscriber, T value)

Method Summary

Modifier and Type	Method	Description
void	cancel()
void	clear()	Removes all enqueued items from this queue.
boolean	isCancelled()	Returns true if this Subscription was cancelled.
boolean	isEmpty()	Returns true if the queue is empty.
boolean	offer(T e)	Atomically enqueue a single value.
boolean	offer(T v1, T v2)	Atomically enqueue two values.
T	poll()	Tries to dequeue a value (non-null) or returns null if the queue is empty.
void	request(long n)
int	requestFusion(int mode)	Request a fusion mode from the upstream.

Methods inherited from class AtomicInteger

accumulateAndGet, addAndGet, compareAndExchange, compareAndExchangeAcquire, compareAndExchangeRelease, compareAndSet, decrementAndGet, doubleValue, floatValue, get, getAcquire, getAndAccumulate, getAndAdd, getAndDecrement, getAndIncrement, getAndSet, getAndUpdate, getOpaque, getPlain, incrementAndGet, intValue, lazySet, longValue, set, setOpaque, setPlain, setRelease, toString, updateAndGet, weakCompareAndSet, weakCompareAndSetAcquire, weakCompareAndSetPlain, weakCompareAndSetRelease, weakCompareAndSetVolatile

Methods inherited from class Number

byteValue, shortValue

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

serialVersionUID

private static final long serialVersionUID

See Also:

• Constant Field Values

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:

• Constant Field Values

REQUESTED

static final int REQUESTED

Request has been called.

See Also:

• Constant Field Values

CANCELLED

static final int CANCELLED

Cancel has been called.

See Also:

• Constant Field Values

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.