1 /*
   2  * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test
  26  * @bug 4687909
  27  * @summary Check Inet6Address.hashCode returns a reasonable spread of hash
  28  *          codes.
  29  * @key randomness
  30  */
  31 import java.net.InetAddress;
  32 import java.net.UnknownHostException;
  33 import java.util.Random;
  34 
  35 public class HashSpread {
  36 
  37     static Random r = new Random();
  38 
  39     /**
  40      * Generate and return a random IPv6 address.
  41      */
  42     static InetAddress randomIPv6Adress() {
  43         StringBuffer sb = new StringBuffer();
  44 
  45         for (int i=0; i<8; i++) {
  46 
  47             if (i > 0)
  48                 sb.append(":");
  49 
  50             for (int j=0; j<4; j++) {
  51                 int v = r.nextInt(16);
  52                 if (v < 10) {
  53                     sb.append(Integer.toString(v));
  54                 } else {
  55                     char c = (char) ('A' + v - 10);
  56                     sb.append(c);
  57                 }
  58             }
  59         }
  60 
  61         try {
  62             return InetAddress.getByName(sb.toString());
  63         } catch (UnknownHostException x) {
  64             throw new Error("Internal error in test");
  65         }
  66     }
  67 
  68     public static void main(String args[]) throws Exception {
  69 
  70         int iterations = 10000;
  71         if (args.length > 0) {
  72             iterations = Integer.parseInt(args[0]);
  73         }
  74 
  75         int MIN_SHORT = (int)Short.MIN_VALUE;
  76         int MAX_SHORT = (int)Short.MAX_VALUE;
  77 
  78         /*
  79          * Iterate through 10k hash codes and count the number
  80          * in the MIN_SHORT-MAX_SHORT range.
  81          */
  82         int narrow = 0;
  83         for (int i=0; i<iterations; i++) {
  84             int hc = randomIPv6Adress().hashCode();
  85             if (hc >= MIN_SHORT && hc <= MAX_SHORT) {
  86                 narrow++;
  87             }
  88         }
  89 
  90         /*
  91          * If >85% of hash codes in the range then fail.
  92          */
  93         double percent = (double)narrow / (double)iterations * 100.0;
  94         if (percent > 85.0) {
  95             throw new RuntimeException(percent + " of hash codes were in " +
  96                 MIN_SHORT + " to " + MAX_SHORT  + " range.");
  97         }
  98 
  99     }
 100 
 101 }