content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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
   *
   *     http://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 org.apache.bookkeeper.net;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkState;
  
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.UnknownHostException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  
  /**
   * Network Utilities.
   */
  public class NetUtils {
  
      /**
       * Given a string representation of a host, return its ip address
       * in textual presentation.
       *
       * @param name a string representation of a host:
       *             either a textual representation its IP address or its host name
       * @return its IP address in the string format
       */
      public static String normalizeHostName(String name) {
          try {
              return InetAddress.getByName(name).getHostAddress();
          } catch (UnknownHostException e) {
              return name;
          }
      }
  
      /**
       * Given a collection of string representation of hosts, return a list of
       * corresponding IP addresses in the textual representation.
       *
       * @param names a collection of string representations of hosts
       * @return a list of corresponding IP addresses in the string format
       * @see #normalizeHostName(String)
       */
      public static List<String> normalizeHostNames(Collection<String> names) {
          List<String> hostNames = new ArrayList<String>(names.size());
          for (String name : names) {
              hostNames.add(normalizeHostName(name));
          }
          return hostNames;
      }
  
      public static String resolveNetworkLocation(DNSToSwitchMapping dnsResolver,
                                                  BookieSocketAddress addr) {
          List<String> names = new ArrayList<String>(1);
  
          InetSocketAddress inetSocketAddress = addr.getSocketAddress();
          if (dnsResolver.useHostName()) {
              names.add(addr.getHostName());
          } else {
              InetAddress inetAddress = inetSocketAddress.getAddress();
              if (null == inetAddress) {
                  names.add(addr.getHostName());
              } else {
                  names.add(inetAddress.getHostAddress());
              }
          }
  
          // resolve network addresses
          List<String> rNames = dnsResolver.resolve(names);
          checkNotNull(rNames, "DNS Resolver should not return null response.");
          checkState(rNames.size() == 1, "Expected exactly one element");
  
          return rNames.get(0);
      }
  
  }
  