com.fluxtion.agrona.concurrent.broadcast.BroadcastBufferDescriptor Maven / Gradle / Ivy

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/*
 * Copyright 2014-2024 Real Logic Limited.
 *
 * 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
 *
 * 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 com.fluxtion.agrona.concurrent.broadcast;

import static com.fluxtion.agrona.BitUtil.*;

/**
 * Layout of the broadcast buffer. The buffer consists of a ring of messages that is a power of 2 in size.
 * This is followed by a trailer section containing state information about the ring.
 */
public final class BroadcastBufferDescriptor
{
    /**
     * Offset within the trailer for where the tail intended value is stored.
     */
    public static final int TAIL_INTENT_COUNTER_OFFSET;

    /**
     * Offset within the trailer for where the tail value is stored.
     */
    public static final int TAIL_COUNTER_OFFSET;

    /**
     * Offset within the trailer for where the latest sequence value is stored.
     */
    public static final int LATEST_COUNTER_OFFSET;

    /**
     * Total size of the trailer.
     */
    public static final int TRAILER_LENGTH;

    static
    {
        int offset = 0;
        TAIL_INTENT_COUNTER_OFFSET = offset;

        offset += SIZE_OF_LONG;
        TAIL_COUNTER_OFFSET = offset;

        offset += SIZE_OF_LONG;
        LATEST_COUNTER_OFFSET = offset;

        TRAILER_LENGTH = CACHE_LINE_LENGTH * 2;
    }

    private BroadcastBufferDescriptor()
    {
    }

    /**
     * Check the buffer capacity is the correct size.
     *
     * @param capacity to be checked.
     * @throws IllegalStateException if the buffer capacity is not a power of 2.
     */
    public static void checkCapacity(final int capacity)
    {
        if (!isPowerOfTwo(capacity))
        {
            final String msg = "capacity must be a positive power of 2 + TRAILER_LENGTH: capacity=" + capacity;
            throw new IllegalStateException(msg);
        }
    }
}