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1   /*
2    * Copyright 2021 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.handler.codec.dns;
17  
18  import io.netty.buffer.ByteBuf;
19  import io.netty.channel.ChannelHandlerContext;
20  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
21  import io.netty.util.internal.ObjectUtil;
22  import io.netty.util.internal.UnstableApi;
23  
24  @UnstableApi
25  public final class TcpDnsQueryDecoder extends LengthFieldBasedFrameDecoder {
26      private final DnsRecordDecoder decoder;
27  
28      /**
29       * Creates a new decoder with {@linkplain DnsRecordDecoder#DEFAULT the default record decoder}.
30       */
31      public TcpDnsQueryDecoder() {
32          this(DnsRecordDecoder.DEFAULT, 65535);
33      }
34  
35      /**
36       * Creates a new decoder with the specified {@code decoder}.
37       */
38      public TcpDnsQueryDecoder(DnsRecordDecoder decoder, int maxFrameLength) {
39          super(maxFrameLength, 0, 2, 0, 2);
40          this.decoder = ObjectUtil.checkNotNull(decoder, "decoder");
41      }
42  
43      @Override
44      protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
45          ByteBuf frame = (ByteBuf) super.decode(ctx, in);
46          if (frame == null) {
47              return null;
48          }
49  
50          return DnsMessageUtil.decodeDnsQuery(decoder, frame.slice(), new DnsMessageUtil.DnsQueryFactory() {
51              @Override
52              public DnsQuery newQuery(int id, DnsOpCode dnsOpCode) {
53                  return new DefaultDnsQuery(id, dnsOpCode);
54              }
55          });
56      }
57  }