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 package test.java.net.InetAddress;
24 
25 /*
26  * @test
27  * @bug 4687909
28  * @summary Check Inet6Address.hashCode returns a reasonable spread of hash
29  *          codes.
30  * @key randomness
31  */
32 import java.net.InetAddress;
33 import java.net.UnknownHostException;
34 import java.util.Random;
35 import org.testng.annotations.Test;
36 import static org.testng.Assert.fail;
37 
38 public class HashSpread {
39 
40     static Random r = new Random();
41 
42     /**
43      * Generate and return a random IPv6 address.
44      */
randomIPv6Adress()45     static InetAddress randomIPv6Adress() {
46         StringBuffer sb = new StringBuffer();
47 
48         for (int i=0; i<8; i++) {
49 
50             if (i > 0)
51                 sb.append(":");
52 
53             for (int j=0; j<4; j++) {
54                 int v = r.nextInt(16);
55                 if (v < 10) {
56                     sb.append(Integer.toString(v));
57                 } else {
58                     char c = (char) ('A' + v - 10);
59                     sb.append(c);
60                 }
61             }
62         }
63 
64         try {
65             return InetAddress.getByName(sb.toString());
66         } catch (UnknownHostException x) {
67             throw new Error("Internal error in test");
68         }
69     }
70 
71     @Test
testHashSpread()72     public void testHashSpread() throws Exception {
73 
74         int iterations = 10000;
75 
76         int MIN_SHORT = (int)Short.MIN_VALUE;
77         int MAX_SHORT = (int)Short.MAX_VALUE;
78 
79         /*
80          * Iterate through 10k hash codes and count the number
81          * in the MIN_SHORT-MAX_SHORT range.
82          */
83         int narrow = 0;
84         for (int i=0; i<iterations; i++) {
85             int hc = randomIPv6Adress().hashCode();
86             if (hc >= MIN_SHORT && hc <= MAX_SHORT) {
87                 narrow++;
88             }
89         }
90 
91         /*
92          * If >85% of hash codes in the range then fail.
93          */
94         double percent = (double)narrow / (double)iterations * 100.0;
95         if (percent > 85.0) {
96             fail(percent + " of hash codes were in " +
97                     MIN_SHORT + " to " + MAX_SHORT  + " range.");
98         }
99 
100     }
101 
102 }