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package com.sun.jaspic.config.helper;

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

/**
 *
 * @author Ron Monzillo
 */

public class EpochCarrier {

    private Lock instanceReadLock;
    private Lock instanceWriteLock;

    private long epoch;

    public EpochCarrier() {
        ReentrantReadWriteLock instanceReadWriteLock = new ReentrantReadWriteLock();
        instanceReadLock = instanceReadWriteLock.readLock();
        instanceWriteLock = instanceReadWriteLock.writeLock();
        epoch = 0L;
    }

    public long increment() {
        instanceWriteLock.lock();
        long before;
        try {
            before = epoch;
            epoch = epoch + 1;
        } finally {
            instanceWriteLock.unlock();
        }
        return before;
    }

    public long getEpoch() {
        instanceReadLock.lock();
        try {
            return epoch;
        } finally {
            instanceReadLock.unlock();
        }
    }

    public boolean hasChanged(long reference) {
        instanceReadLock.lock();
        try {
            return epoch != reference;
        } finally {
            instanceReadLock.unlock();
        }
    }

}