content: /*
   * Copyright 2012-2021 Aerospike, Inc.
   *
   * Portions may be licensed to Aerospike, Inc. under one or more contributor
   * license agreements WHICH ARE COMPATIBLE WITH THE APACHE LICENSE, VERSION 2.0.
   *
   * Licensed 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 com.aerospike.client.async;
  
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  
  /**
   * Limit the number of commands allowed at any point in time.
   */
  public final class Throttle {
  	private final ReentrantLock lock;
  	private final Condition avail;
  	private int available;
  
  	/**
  	 * Construct throttle with max number of commands.
  	 */
  	public Throttle(int capacity) {
  		lock = new ReentrantLock(false);
  		avail = lock.newCondition();
  		available = capacity;
  	}
  
  	/**
  	 * Wait for command slot(s).
  	 *
  	 * @param count		count of commands to reserve
  	 * @return			if command should be processed
  	 */
  	public boolean waitForSlot(int count) {
  		try {
  			final ReentrantLock lock = this.lock;
  			lock.lockInterruptibly();
  			try {
  				while (available < count) {
  					avail.await();
  				}
  				available -= count;
  				return true;
  			}
  			finally {
  				lock.unlock();
  			}
  		}
  		catch (InterruptedException ie) {
  			return false;
  		}
  	}
  
  	/**
  	 * Recover slot(s) from commands that have completed.
  	 *
  	 * @param count		count of commands to reclaim
  	 */
  	public void addSlot(int count) {
  		lock.lock();
  		try {
  			available += count;
  			avail.signal();
  		}
  		finally {
  			lock.unlock();
  		}
  	}
  
  	/**
  	 * Get current number of commands that could be run.
  	 */
  	public int getAvailable() {
  		return available;
  	}
  }
  