/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
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 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
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package com.sun.enterprise.util;

import java.io.Serializable;

/**
 * Represents a block of unique numbers reserved for a particular
 * context by the backend value generator.  This class should
 * only be used internally by concrete UniqueValueGenerator implementations.
 * 
 * @author Kenneth Saks
 */
public class UniqueValueBlock implements Serializable {
    
    // Lowest value available
    private long start_;
    
    // Number of values available in this block
    private long extent_;

    // Current value
    private long current_;

    /**
     * Use package-level access since this class should only be
     * used internally by concrete instances of UniqueValueGenerator.
     * The extent value must be >= 1.
     */
    UniqueValueBlock(long start, long extent) {
        start_   = start;
        extent_  = extent;
        current_ = start;
    }
    
    public synchronized boolean hasNext() {
        return (current_ < (start_ + extent_));
    }

    public synchronized long next() {
        if( !hasNext() ) {
            throw new IllegalStateException();
        }
        long returnValue = current_;
        current_++;
        return returnValue;
    }
}