content: /**
   * 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.activemq.transport.discovery.zeroconf;
  
  import java.io.IOException;
  import java.net.InetAddress;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.concurrent.atomic.AtomicInteger;
  import javax.jmdns.JmDNS;
  
  public final class JmDNSFactory {
  
      static Map<InetAddress, UsageTracker> registry = new HashMap<InetAddress, UsageTracker>();
  
      static class UsageTracker {
          AtomicInteger count = new AtomicInteger(0);
          JmDNS jmDNS;
      }
  
      private JmDNSFactory() {        
      }
      
      static synchronized JmDNS create(final InetAddress address) throws IOException {
          UsageTracker tracker = registry.get(address);
          if (tracker == null) {
              tracker = new UsageTracker();
              tracker.jmDNS = JmDNS.create(address);
              registry.put(address, tracker);
          }
          tracker.count.incrementAndGet();
          return tracker.jmDNS;
      }
  
      static synchronized boolean onClose(InetAddress address) {
          UsageTracker tracker = registry.get(address);
          if (tracker != null) {
              if (tracker.count.decrementAndGet() == 0) {
                  registry.remove(address);
                  return true;
              }
          }
          return false;
      }
  }
  