MpscIntQueue.java — netty Source File

Source Code

/*
 * Copyright 2025 The Netty Project
 *
 * The Netty Project licenses this file to you 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:
 *
 *   https://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.netty.util.concurrent;

import io.netty.util.internal.MathUtil;
import io.netty.util.internal.ObjectUtil;

import java.util.Objects;
import java.util.concurrent.atomic.AtomicIntegerArray;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.function.IntConsumer;
import java.util.function.IntSupplier;

/**
 * A multi-producer (concurrent and thread-safe {@code offer} and {@code fill}),
 * single-consumer (single-threaded {@code poll} and {@code drain}) queue of primitive integers.
 */
public interface MpscIntQueue {
    /**
     * Create a new queue instance of the given size.
     * <p>
     * Note: the size of the queue may be rounded up to nearest power-of-2.
     *
     * @param size The required fixed size of the queue.
     * @param emptyValue The special value that the queue should use to signal the "empty" case.
     * This value will be returned from {@link #poll()} when the queue is empty,
     * and giving this value to {@link #offer(int)} will cause an exception to be thrown.
     * @return The queue instance.
     */
    static MpscIntQueue create(int size, int emptyValue) {
        return new MpscAtomicIntegerArrayQueue(size, emptyValue);
    }

    /**
     * Offer the given value to the queue. This will throw an exception if the given value is the "empty" value.
     * @param value The value to add to the queue.
     * @return {@code true} if the value was added to the queue,
     * or {@code false} if the value could not be added because the queue is full.
     */
    boolean offer(int value);

    /**
     * Remove and return the next value from the queue, or return the "empty" value if the queue is empty.
     * @return The next value or the "empty" value.
     */
    int poll();

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