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/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.internal.fuseable;
import io.reactivex.annotations.*;
/**
* A minimalist queue interface without the method bloat of java.util.Collection and java.util.Queue.
*
* @param the value type to offer and poll, not null
*/
public interface SimpleQueue {
/**
* Atomically enqueue a single.
* @param value the value to enqueue, not null
* @return true if successful, false if the value was not enqueued
* likely due to reaching the queue capacity)
*/
boolean offer(@NonNull T value);
/**
* Atomically enqueue two values.
* @param v1 the first value to enqueue, not null
* @param v2 the second value to enqueue, not null
* @return true if successful, false if the value was not enqueued
* likely due to reaching the queue capacity)
*/
boolean offer(@NonNull T v1, @NonNull T v2);
/**
* Tries to dequeue a value (non-null) or returns null if
* the queue is empty.
*
* If the producer uses {@link #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.
* @return the item or null to indicate an empty queue
* @throws Exception if some pre-processing of the dequeued
* item (usually through fused functions) throws.
*/
@Nullable
T poll() throws Exception;
/**
* Returns true if the queue is empty.
*
* Note however that due to potential fused functions in {@link #poll()}
* it is possible this method returns false but then poll() returns null
* because the fused function swallowed the available item(s).
* @return true if the queue is empty
*/
boolean isEmpty();
/**
* Removes all enqueued items from this queue.
*/
void clear();
}