org.reactivestreams.Subscription.scala Maven / Gradle / Ivy
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/*
* Copyright (c) 2014-2019 by The Monix Project Developers.
* See the project homepage at: https://monix.io
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.reactivestreams
/**
* Represents a one-to-one lifecycle of a [[Subscriber]] subscribing to a [[Publisher]]
* and mirrors the `Subscription` interface from the
* [[http://www.reactive-streams.org/ Reactive Streams]] specification.
*
* It can be used only once by a single [[Subscriber]]. It is used
* for both signaling demand for data and for canceling demand (and allow
* resource cleanup).
*/
trait Subscription {
/**
* No events will be sent by a [[Publisher]] until demand is signaled via this method.
*
* It can be called however often and whenever needed.
* Whatever has been requested can be sent by the [[Publisher]]
* so only signal demand for what can be safely handled.
*
* A [[Publisher]] can send less than is requested if the stream ends but
* then must emit either `onError` or `onComplete`.
*
* The [[Subscriber]] MAY call this method synchronously in the implementation of its
* `onSubscribe` / `onNext` methods, therefore the effects of this function must be
* asynchronous, otherwise it could lead to a stack overflow.
*
* @param n signals demand for the number of `onNext` events that the [[Subscriber]] wants,
* if positive, then the [[Publisher]] is bound by contract to not send more than
* this number of `onNext` events and if negative, then this signals to the
* [[Publisher]] that it may send an infinite number of events, until the subscription
* gets cancelled or the stream is complete.
*/
def request(n: Long): Unit
/**
* Request the [[Publisher]] to stop sending data and clean up resources.
*
* Data may still be sent to meet previously signalled demand after
* calling cancel as this request is asynchronous.
*/
def cancel(): Unit
}