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   /*
    * Copyright 2016 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.handler.codec.dns;
  
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  import io.netty.util.internal.StringUtil;
  import io.netty.util.internal.UnstableApi;
  
  @UnstableApi
  public class DefaultDnsPtrRecord extends AbstractDnsRecord implements DnsPtrRecord {
  
      private final String hostname;
  
      /**
       * Creates a new PTR record.
       *
       * @param name the domain name
       * @param dnsClass the class of the record, usually one of the following:
       *                 <ul>
       *                     <li>{@link #CLASS_IN}</li>
       *                     <li>{@link #CLASS_CSNET}</li>
       *                     <li>{@link #CLASS_CHAOS}</li>
       *                     <li>{@link #CLASS_HESIOD}</li>
       *                     <li>{@link #CLASS_NONE}</li>
       *                     <li>{@link #CLASS_ANY}</li>
       *                 </ul>
       * @param timeToLive the TTL value of the record
       * @param hostname the hostname this PTR record resolves to.
       */
      public DefaultDnsPtrRecord(
              String name, int dnsClass, long timeToLive, String hostname) {
          super(name, DnsRecordType.PTR, dnsClass, timeToLive);
          this.hostname = checkNotNull(hostname, "hostname");
      }
  
      @Override
      public String hostname() {
          return hostname;
      }
  
      @Override
      public String toString() {
          final StringBuilder buf = new StringBuilder(64).append(StringUtil.simpleClassName(this)).append('(');
          final DnsRecordType type = type();
          buf.append(name().isEmpty()? "<root>" : name())
             .append(' ')
             .append(timeToLive())
             .append(' ');
  
          DnsMessageUtil.appendRecordClass(buf, dnsClass())
                        .append(' ')
                        .append(type.name());
  
          buf.append(' ')
             .append(hostname);
  
          return buf.toString();
      }
  }