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   /*
    * Copyright 2023 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.resolver.dns;
  
  import io.netty.handler.codec.dns.DnsResponseCode;
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.SuppressJava6Requirement;
  import io.netty.util.internal.ThrowableUtil;
  
  import java.net.UnknownHostException;
  
  /**
   * A metadata carrier exception, to propagate {@link DnsResponseCode} information as an enrichment
   * within the {@link UnknownHostException} cause.
   */
  public final class DnsErrorCauseException extends RuntimeException {
  
      private static final long serialVersionUID = 7485145036717494533L;
  
      private final DnsResponseCode code;
  
      private DnsErrorCauseException(String message, DnsResponseCode code) {
          super(message);
          this.code = code;
      }
  
      @SuppressJava6Requirement(reason = "uses Java 7+ Exception.<init>(String, Throwable, boolean, boolean)" +
              " but is guarded by version checks")
      private DnsErrorCauseException(String message, DnsResponseCode code, boolean shared) {
          super(message, null, false, true);
          this.code = code;
          assert shared;
      }
  
      // Override fillInStackTrace() so we not populate the backtrace via a native call and so leak the
      // Classloader.
      @Override
      public Throwable fillInStackTrace() {
          return this;
      }
  
      /**
       * Returns the DNS error-code that caused the {@link UnknownHostException}.
       *
       * @return the DNS error-code that caused the {@link UnknownHostException}.
       */
      public DnsResponseCode getCode() {
          return code;
      }
  
      static DnsErrorCauseException newStatic(String message, DnsResponseCode code, Class<?> clazz, String method) {
          final DnsErrorCauseException exception;
          if (PlatformDependent.javaVersion() >= 7) {
              exception = new DnsErrorCauseException(message, code, true);
          } else {
              exception = new DnsErrorCauseException(message, code);
          }
          return ThrowableUtil.unknownStackTrace(exception, clazz, method);
      }
  }