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   /*
    * Copyright 2024 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.util.concurrent.FastThreadLocal;
  
  import java.net.InetSocketAddress;
  
  /**
   * A thread local based address stream for a specific hostname.
   */
  final class ThreadLocalNameServerAddressStream implements DnsServerAddressStream {
  
      private final String hostname;
      private final DnsServerAddressStreamProvider dnsServerAddressStreamProvider;
      private final FastThreadLocal<DnsServerAddressStream> threadLocal = new FastThreadLocal<DnsServerAddressStream>() {
          @Override
          protected DnsServerAddressStream initialValue() {
              return dnsServerAddressStreamProvider.nameServerAddressStream(hostname);
          }
      };
  
      ThreadLocalNameServerAddressStream(DnsServerAddressStreamProvider dnsServerAddressStreamProvider) {
          this(dnsServerAddressStreamProvider, "");
      }
  
      ThreadLocalNameServerAddressStream(DnsServerAddressStreamProvider dnsServerAddressStreamProvider, String hostname) {
          this.dnsServerAddressStreamProvider = dnsServerAddressStreamProvider;
          this.hostname = hostname;
      }
  
      @Override
      public InetSocketAddress next() {
          return threadLocal.get().next();
      }
  
      @Override
      public DnsServerAddressStream duplicate() {
          return new ThreadLocalNameServerAddressStream(dnsServerAddressStreamProvider, hostname);
      }
  
      @Override
      public int size() {
          return threadLocal.get().size();
      }
  }