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 *     ___                  _   ____  ____
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 *
 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2020 QuestDB
 *
 *  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.
 *
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package io.questdb.mp;

import io.questdb.std.Unsafe;

public abstract class SynchronizedJob implements Job {
    private static final long LOCKED_OFFSET = Unsafe.getFieldOffset(SynchronizedJob.class, "locked");

    @SuppressWarnings({"unused", "FieldCanBeLocal"})
    private volatile int locked = 0;

    @Override
    public boolean run(int workerId) {
        if (Unsafe.getUnsafe().compareAndSwapInt(this, LOCKED_OFFSET, 0, 1)) {
            try {
                return runSerially();
            } finally {
                locked = 0;
            }
        }
        return false;
    }

    protected abstract boolean runSerially();
}