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1   /*
2    * Copyright 2018 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.resolver.dns;
17  
18  import io.netty.channel.EventLoop;
19  
20  /**
21   * A cache for {@code CNAME}s.
22   */
23  public interface DnsCnameCache {
24  
25      /**
26       * Returns the cached cname for the given hostname.
27       *
28       * @param hostname the hostname
29       * @return the cached entries or an {@code null} if none.
30       */
31      String get(String hostname);
32  
33      /**
34       * Caches a cname entry that should be used for the given hostname.
35       *
36       * @param hostname the hostname
37       * @param cname the cname mapping.
38       * @param originalTtl the TTL as returned by the DNS server
39       * @param loop the {@link EventLoop} used to register the TTL timeout
40       */
41      void cache(String hostname, String cname, long originalTtl, EventLoop loop);
42  
43      /**
44       * Clears all cached nameservers.
45       *
46       * @see #clear(String)
47       */
48      void clear();
49  
50      /**
51       * Clears the cached nameservers for the specified hostname.
52       *
53       * @return {@code true} if and only if there was an entry for the specified host name in the cache and
54       *         it has been removed by this method
55       */
56      boolean clear(String hostname);
57  }