Module io.helidon.common.reactive

Package io.helidon.common.reactive

Enum SubscriptionHelper

java.lang.Object

java.lang.Enum<SubscriptionHelper>

io.helidon.common.reactive.SubscriptionHelper

All Implemented Interfaces:

Serializable, Comparable<SubscriptionHelper>, Flow.Subscription

public enum SubscriptionHelper
extends Enum<SubscriptionHelper>
implements Flow.Subscription

Helper enum with a singleton cancellation indicator and utility methods to perform atomic actions on Flow.Subscriptions.

Enum Constant Summary

Enum Constants

Enum Constant	Description
BAD_REQUEST	The singleton instance indicating a subscription requested with non-positive.
CANCELED	The singleton instance indicating a canceled subscription.

Method Summary

Modifier and Type	Method	Description
static long	addRequest(AtomicLong field, long n)	Atomically add the given request amount to the field while capping it at Long.MAX_VALUE.
static boolean	badRequest(AtomicReference<Flow.Subscription> subscriptionField)	Atomically swap in the BAD_REQUEST instance, if and only if previous value is null.
void	cancel()
static boolean	cancel(AtomicReference<Flow.Subscription> subscriptionField)	Atomically swap in the CANCELED instance and call cancel() on any previous Subscription held.
static void	deferredRequest(AtomicReference<Flow.Subscription> subscriptionField, AtomicLong requestedField, long n)	Accumulates request amounts until the subscription field receives a Subscription instance, then requests this accumulated amount and forwards subsequent requests to it.
static boolean	deferredSetOnce(AtomicReference<Flow.Subscription> subscriptionField, AtomicLong requestedField, Flow.Subscription upstream)	Atomically sets the only upstream subscription in the field and then requests the amount accumulated in the requestedField.
static long	produced(AtomicLong field, long n)	Atomically subtract the given number from the field if that field is not already at Long.MAX_VALUE and return the new value.
static void	replace(AtomicReference<Flow.Subscription> field, Flow.Subscription incoming)	Atomically swap in the given incoming Flow.Subscription or cancel it if the target field is canceled.
void	request(long n)
static boolean	setOnce(AtomicReference<Flow.Subscription> subscriptionField, Flow.Subscription upstream)	Atomically sets the only upstream subscription in the field.
static void	validate(Flow.Subscription current, Flow.Subscription incoming)	Check if current is null and incoming is not null.
static SubscriptionHelper	valueOf(String name)	Returns the enum constant of this type with the specified name.
static SubscriptionHelper[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

CANCELED

public static final SubscriptionHelper CANCELED

The singleton instance indicating a canceled subscription.

BAD_REQUEST

public static final SubscriptionHelper BAD_REQUEST

The singleton instance indicating a subscription requested with non-positive.

Method Detail

values

public static SubscriptionHelper[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (SubscriptionHelper c : SubscriptionHelper.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static SubscriptionHelper valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

request

public void request(long n)

Specified by:

request in interface Flow.Subscription

cancel

public void cancel()

Specified by:

cancel in interface Flow.Subscription

addRequest

public static long addRequest(AtomicLong field,
                              long n)

Atomically add the given request amount to the field while capping it at Long.MAX_VALUE.

Parameters:

field - the target field to update

n - the request amount to add, must be positive (not verified)

Returns:

the old request amount after the operation

produced

public static long produced(AtomicLong field,
                            long n)

Atomically subtract the given number from the field if that field is not already at Long.MAX_VALUE and return the new value.

Parameters:

field - the target field to update

n - the number to subtract

Returns:

the new value after the subtraction

Throws:

IllegalStateException - if n is bigger than the field's value, which indicates an operator bug

setOnce

public static boolean setOnce(AtomicReference<Flow.Subscription> subscriptionField,
                              Flow.Subscription upstream)

Atomically sets the only upstream subscription in the field.

Parameters:

subscriptionField - the field to store the only upstream subscription

upstream - the only upstream to set and request from

Returns:

true if the operation succeeded, false if the field holds the cancellation indicator

Throws:

IllegalStateException - if the subscriptionField already contains a non-canceled subscription instance

deferredSetOnce

public static boolean deferredSetOnce(AtomicReference<Flow.Subscription> subscriptionField,
                                      AtomicLong requestedField,
                                      Flow.Subscription upstream)

Atomically sets the only upstream subscription in the field and then requests the amount accumulated in the requestedField.

Parameters:

subscriptionField - the field to store the only upstream subscription

requestedField - the request amounts accumulated so far

upstream - the only upstream to set and request from

Returns:

true if the operation succeeded, false if the field indicated the upstream should be cancelled immediately

Throws:

IllegalStateException - if the subscriptionField already contains a non-canceled subscription instance

deferredRequest

public static void deferredRequest(AtomicReference<Flow.Subscription> subscriptionField,
                                   AtomicLong requestedField,
                                   long n)

Accumulates request amounts until the subscription field receives a Subscription instance, then requests this accumulated amount and forwards subsequent requests to it.

Parameters:

subscriptionField - the field possibly containing a Subscription instance.

requestedField - the field used for accumulating requests until the Subscription instance arrives

n - the request amount to accumulate or forward, must be positive (not verified)

cancel

public static boolean cancel(AtomicReference<Flow.Subscription> subscriptionField)

Atomically swap in the CANCELED instance and call cancel() on any previous Subscription held.

Parameters:

subscriptionField - the target field to cancel atomically.

Returns:

true if the current thread succeeded with the cancellation (as only one thread is able to)

badRequest

public static boolean badRequest(AtomicReference<Flow.Subscription> subscriptionField)

Atomically swap in the BAD_REQUEST instance, if and only if previous value is null.

Parameters:

subscriptionField - the target field to swap atomically.

Returns:

true if swap was successful

validate

public static void validate(Flow.Subscription current,
                            Flow.Subscription incoming)

Check if current is null and incoming is not null.

Parameters:

current - the current subscription, should be null

incoming - the incoming subscription, should be non-null

Throws:

IllegalStateException - if current is not-null indicating a bug in an operator calling onSubscribe more than once

replace

public static void replace(AtomicReference<Flow.Subscription> field,
                           Flow.Subscription incoming)

Atomically swap in the given incoming Flow.Subscription or cancel it if the target field is canceled.

Parameters:

field - the target field

incoming - the incoming subscription, nulls allowed