# ConcurrentAccessController.java

    /*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF licenses this file
    *  to you under the Apache License, Version 2.0 (the
    *  "License"); you may not use this file except in compliance
    *  with the License.  You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
    *
    *  Unless required by applicable law or agreed to in writing,
    *  software distributed under the License is distributed on an
    *   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    *  KIND, either express or implied.  See the License for the
    *  specific language governing permissions and limitations
    *  under the License.
    */
    package org.apache.synapse.commons.throttle.core;

    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;

    import java.io.Serializable;
    import java.util.concurrent.atomic.AtomicInteger;

    /**
     * Controls the concurrent access through throttle to the system based on policy
     */

    public class ConcurrentAccessController implements Serializable {

    	private static Log log = LogFactory.getLog(ConcurrentAccessController.class.getName());

    	/* The Max number of concurrent access */
    	private int limit;
    	/* The counter variable - hold current access count */
    	private AtomicInteger counter;

    	private static final long serialVersionUID = -6857325377726757251L;

    	public ConcurrentAccessController(int limit) {
    		this.limit = limit;
    		this.counter = new AtomicInteger(limit);
    	}

    	/**
    	 * Decrements by one the current value and Returns the previous value
    	 *
    	 * @return the previous value
    	 */
    	public int getAndDecrement() {
    		int ret = this.counter.getAndDecrement();
    		if (ret <= 0) {
    			this.counter.incrementAndGet();
    			return 0;
    		} else {
    			return ret;
    		}
    	}

    	/**
    	 * Increments by one the current value and Returns the the updated value
    	 *
    	 * @return the updated value
    	 */
    	public int incrementAndGet() {
    		int ret = this.counter.incrementAndGet();
    		if (ret < 0) {
    			return 0;
    		}
    		return ret;
    	}

    	/**
    	 * Gets  the Max number of access - access limit
    	 *
    	 * @return the limit
    	 */
    	public int getLimit() {
    		return this.limit;
    	}

    	/**
    	 * Resets the counter and the limit
    	 *
    	 * @param newValue The new Value
    	 */
    	public void set(int newValue) {
    		this.counter.set(newValue);
    		this.limit = newValue;
    	}

    }