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/*
 * Copyright (c) 1998-2018 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * Resin Open Source 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, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *
 *   Free Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.env.meter;

import java.util.concurrent.atomic.AtomicLong;


public final class SampleCountMeter extends AbstractMeter {
  private final AtomicLong _count = new AtomicLong();
  private final AtomicLong _lastCount = new AtomicLong();
  
  private long _value;

  public SampleCountMeter(String name)
  {
    super(name);
  }

  public final void addData()
  {
    _count.incrementAndGet();
  }
  
  /**
   * Return the probe's next sample.
   */
  @Override
  public final void sample()
  {
    long count = _count.get();
    long lastCount = _lastCount.getAndSet(count);
    
    _value = count - lastCount;
  }
  
  @Override
  public final double calculate()
  {
    return _value;
  }
}