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 * Copyright (C) 2014-2019 Appsicle
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 *
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package com.questdb.mp;

import com.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() {
        if (Unsafe.getUnsafe().compareAndSwapInt(this, LOCKED_OFFSET, 0, 1)) {
            try {
                return runSerially();
            } finally {
                locked = 0;
            }
        }
        return false;
    }

    protected abstract boolean runSerially();
}