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   /*
    * Copyright 2012 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.channel.socket;
  
  import io.netty.util.NetUtil;
  
  import java.net.Inet4Address;
  import java.net.Inet6Address;
  import java.net.InetAddress;
  
  /**
   * Internet Protocol (IP) families used byte the {@link DatagramChannel}
   */
  public enum InternetProtocolFamily {
      IPv4(Inet4Address.class, 1),
      IPv6(Inet6Address.class, 2);
  
      private final Class<? extends InetAddress> addressType;
      private final int addressNumber;
  
      InternetProtocolFamily(Class<? extends InetAddress> addressType, int addressNumber) {
          this.addressType = addressType;
          this.addressNumber = addressNumber;
      }
  
      /**
       * Returns the address type of this protocol family.
       */
      public Class<? extends InetAddress> addressType() {
          return addressType;
      }
  
      /**
       * Returns the
       * <a href="https://www.iana.org/assignments/address-family-numbers/address-family-numbers.xhtml">address number</a>
       * of the family.
       */
      public int addressNumber() {
          return addressNumber;
      }
  
      /**
       * Returns the {@link InetAddress} that represent the {@code LOCALHOST} for the family.
       */
      public InetAddress localhost() {
          switch (this) {
              case IPv4:
                  return NetUtil.LOCALHOST4;
              case IPv6:
                  return NetUtil.LOCALHOST6;
              default:
                  throw new IllegalStateException("Unsupported family " + this);
          }
      }
  
      /**
       * Returns the {@link InternetProtocolFamily} for the given {@link InetAddress}.
       */
      public static InternetProtocolFamily of(InetAddress address) {
          if (address instanceof Inet4Address) {
              return IPv4;
          }
          if (address instanceof Inet6Address) {
              return IPv6;
          }
          throw new IllegalArgumentException("address " + address + " not supported");
      }
  }