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