查看本类的 API文档回源码主页

   /*
    * Copyright 2021 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 io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
  import io.netty.util.internal.ObjectUtil;
  import io.netty.util.internal.UnstableApi;
  
  @UnstableApi
  public final class TcpDnsQueryDecoder extends LengthFieldBasedFrameDecoder {
      private final DnsRecordDecoder decoder;
  
      /**
       * Creates a new decoder with {@linkplain DnsRecordDecoder#DEFAULT the default record decoder}.
       */
      public TcpDnsQueryDecoder() {
          this(DnsRecordDecoder.DEFAULT, 65535);
      }
  
      /**
       * Creates a new decoder with the specified {@code decoder}.
       */
      public TcpDnsQueryDecoder(DnsRecordDecoder decoder, int maxFrameLength) {
          super(maxFrameLength, 0, 2, 0, 2);
          this.decoder = ObjectUtil.checkNotNull(decoder, "decoder");
      }
  
      @Override
      protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
          ByteBuf frame = (ByteBuf) super.decode(ctx, in);
          if (frame == null) {
              return null;
          }
  
          return DnsMessageUtil.decodeDnsQuery(decoder, frame.slice(), new DnsMessageUtil.DnsQueryFactory() {
              @Override
              public DnsQuery newQuery(int id, DnsOpCode dnsOpCode) {
                  return new DefaultDnsQuery(id, dnsOpCode);
              }
          });
      }
  }