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/*
 * TeleStax, Open Source Cloud Communications
 * Copyright 2011-2016, TeleStax Inc. and individual contributors
 * by the @authors tag.
 *
 * This program is free software: you can redistribute it and/or modify
 * under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * 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 
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 *   JBoss, Home of Professional Open Source
 *   Copyright 2007-2011, Red Hat, Inc. and individual contributors
 *   by the @authors tag. See the copyright.txt in the distribution for a
 *   full listing of individual contributors.
 *
 *   This is free software; you can redistribute it and/or modify it
 *   under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation; either version 2.1 of
 *   the License, or (at your option) any later version.
 *
 *   This software 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
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this software; if not, write to the Free
 *   Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 *   02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.jdiameter.client.impl.helpers;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * This class provide uid range generator functionality
 *
 * @author [email protected]
 * @author  Alexandre Mendonca 
 * @author  Bartosz Baranowski 
 */
@SuppressWarnings("all") //3rd party lib
public class UIDGenerator { // todo remove or redesign

    private /* static */ long value; // static causes repetitions
    private static final Lock mutex = new ReentrantLock();
    private static final ThreadLocal ranges = new ThreadLocal() {
        @Override
        protected synchronized Delta initialValue() {
            return new Delta();
        }
    };

    private static class Delta {
        long start;
        long stop;

        public long update(long value) {
            start = value;
            stop = value + 1;
            return stop;
        }
    }

    /**
     * Create instance of class
     */
    public UIDGenerator() {
        value = System.currentTimeMillis();
    }

    /**
     * Create instance of class with predefined start value
     *
     * @param startValue start value of counter
     */
    public UIDGenerator(long startValue) {
        value = startValue;
    }

    /**
     * Return next uid as int
     *
     * @return uid
     */
    public int nextInt() {
        return (int) (0x7FFFFFFF & nextLong());
    }

    /**
     * Return next uid as long
     *
     * @return uid as long
     */
    public long nextLong() {
        Delta d = ranges.get();
        if (d.start <= d.stop) {
            mutex.lock();
            value = d.update(value);
            mutex.unlock();
        }
        return d.start++;
    }
}