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   /*
    * Copyright 2017 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.resolver.dns;
  
  import io.netty.channel.ChannelFuture;
  import io.netty.handler.codec.dns.DnsQuestion;
  import io.netty.handler.codec.dns.DnsResponseCode;
  
  import java.net.InetSocketAddress;
  import java.util.List;
  
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  /**
   * Combines two {@link DnsQueryLifecycleObserver} into a single {@link DnsQueryLifecycleObserver}.
   */
  public final class BiDnsQueryLifecycleObserver implements DnsQueryLifecycleObserver {
      private final DnsQueryLifecycleObserver a;
      private final DnsQueryLifecycleObserver b;
  
      /**
       * Create a new instance.
       * @param a The {@link DnsQueryLifecycleObserver} that will receive events first.
       * @param b The {@link DnsQueryLifecycleObserver} that will receive events second.
       */
      public BiDnsQueryLifecycleObserver(DnsQueryLifecycleObserver a, DnsQueryLifecycleObserver b) {
          this.a = checkNotNull(a, "a");
          this.b = checkNotNull(b, "b");
      }
  
      @Override
      public void queryWritten(InetSocketAddress dnsServerAddress, ChannelFuture future) {
          try {
              a.queryWritten(dnsServerAddress, future);
          } finally {
              b.queryWritten(dnsServerAddress, future);
          }
      }
  
      @Override
      public void queryCancelled(int queriesRemaining) {
          try {
              a.queryCancelled(queriesRemaining);
          } finally {
              b.queryCancelled(queriesRemaining);
          }
      }
  
      @Override
      public DnsQueryLifecycleObserver queryRedirected(List<InetSocketAddress> nameServers) {
          try {
              a.queryRedirected(nameServers);
          } finally {
              b.queryRedirected(nameServers);
          }
          return this;
      }
  
      @Override
      public DnsQueryLifecycleObserver queryCNAMEd(DnsQuestion cnameQuestion) {
          try {
              a.queryCNAMEd(cnameQuestion);
          } finally {
              b.queryCNAMEd(cnameQuestion);
          }
          return this;
      }
  
      @Override
      public DnsQueryLifecycleObserver queryNoAnswer(DnsResponseCode code) {
          try {
              a.queryNoAnswer(code);
          } finally {
              b.queryNoAnswer(code);
          }
          return this;
      }
  
      @Override
      public void queryFailed(Throwable cause) {
          try {
              a.queryFailed(cause);
          } finally {
              b.queryFailed(cause);
          }
      }
 
     @Override
     public void querySucceed() {
         try {
             a.querySucceed();
         } finally {
             b.querySucceed();
         }
     }
 }