1 /*
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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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9  * This code is distributed in the hope that it will be useful, but WITHOUT
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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  *
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23 
24 import java.io.*;
25 import java.lang.reflect.Field;
26 import java.util.Hashtable;
27 
28 /**
29  * @test
30  * @bug 8068427
31  * @summary Hashtable deserialization reconstitutes table with wrong capacity
32  * @modules java.base/java.util:open
33  */
34 public class DeserializedLength {
35 
testDeserializedLength(int elements, float loadFactor)36     static boolean testDeserializedLength(int elements, float loadFactor) throws Exception {
37 
38         // construct Hashtable with minimal initial capacity and given loadFactor
39         Hashtable<Integer, Integer> ht1 = new Hashtable<>(1, loadFactor);
40 
41         // add given number of unique elements
42         for (int i = 0; i < elements; i++) {
43             ht1.put(i, i);
44         }
45 
46         // serialize and deserialize into a deep clone
47         Hashtable<Integer, Integer> ht2 = serialClone(ht1);
48 
49         // compare lengths of internal tables
50         Object[] table1 = (Object[]) hashtableTableField.get(ht1);
51         Object[] table2 = (Object[]) hashtableTableField.get(ht2);
52         assert table1 != null;
53         assert table2 != null;
54 
55         int minLength = (int) (ht1.size() / loadFactor) + 1;
56         int maxLength = minLength * 2;
57 
58         boolean ok = (table2.length >= minLength && table2.length <= maxLength);
59 
60         System.out.printf(
61             "%7d %5.2f %7d %7d %7d...%7d %s\n",
62             ht1.size(), loadFactor,
63             table1.length, table2.length,
64             minLength, maxLength,
65             (ok ? "OK" : "NOT-OK")
66         );
67 
68         return ok;
69     }
70 
serialClone(T o)71     static <T> T serialClone(T o) throws IOException, ClassNotFoundException {
72         ByteArrayOutputStream bos = new ByteArrayOutputStream();
73         try (ObjectOutputStream oos = new ObjectOutputStream(bos)) {
74             oos.writeObject(o);
75         }
76         @SuppressWarnings("unchecked")
77         T clone = (T) new ObjectInputStream(
78             new ByteArrayInputStream(bos.toByteArray())).readObject();
79         return clone;
80     }
81 
82     private static final Field hashtableTableField;
83 
84     static {
85         try {
86             hashtableTableField = Hashtable.class.getDeclaredField("table");
87             hashtableTableField.setAccessible(true);
88         } catch (NoSuchFieldException e) {
89             throw new Error(e);
90         }
91     }
92 
main(String[] args)93     public static void main(String[] args) throws Exception {
94         boolean ok = true;
95 
96         System.out.printf("Results:\n" +
97                 "                 ser.  deser.\n" +
98                 "   size  load  lentgh  length       valid range ok?\n" +
99                 "------- ----- ------- ------- ----------------- ------\n"
100         );
101 
102         for (int elements : new int[]{10, 50, 500, 5000}) {
103             for (float loadFactor : new float[]{0.15f, 0.5f, 0.75f, 1.0f, 2.5f}) {
104                 ok &= testDeserializedLength(elements, loadFactor);
105             }
106         }
107         if (!ok) {
108             throw new AssertionError("Test failed.");
109         }
110     }
111 }
112