1/*
2 * Copyright 2016 Google, Inc.  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 8146568
27 * @summary brittle white box test of internal array management
28 * @modules java.base/java.util:open
29 * @run testng ArrayManagement
30 */
31
32import java.lang.reflect.Field;
33import java.util.AbstractList;
34import java.util.ArrayList;
35import java.util.Collections;
36import java.util.List;
37import java.util.SplittableRandom;
38
39import org.testng.annotations.Test;
40import static org.testng.Assert.*;
41
42public class ArrayManagement {
43    static final int DEFAULT_CAPACITY = 10;
44    static final Field ELEMENT_DATA;
45    static final Field MODCOUNT;
46    static final SplittableRandom rnd = new SplittableRandom();
47
48    static {
49        try {
50            ELEMENT_DATA = ArrayList.class.getDeclaredField("elementData");
51            ELEMENT_DATA.setAccessible(true);
52            MODCOUNT = AbstractList.class.getDeclaredField("modCount");
53            MODCOUNT.setAccessible(true);
54        } catch (ReflectiveOperationException huh) {
55            throw new AssertionError(huh);
56        }
57    }
58
59    static Object[] elementData(ArrayList<?> list) {
60        try {
61            return (Object[]) ELEMENT_DATA.get(list);
62        } catch (ReflectiveOperationException huh) {
63            throw new AssertionError(huh);
64        }
65    }
66
67    static int modCount(ArrayList<?> list) {
68        try {
69            return MODCOUNT.getInt(list);
70        } catch (ReflectiveOperationException huh) {
71            throw new AssertionError(huh);
72        }
73    }
74
75    static int capacity(ArrayList<?> list) {
76        return elementData(list).length;
77    }
78
79    static int newCapacity(int oldCapacity) {
80        return oldCapacity + (oldCapacity >> 1);
81    }
82
83    static void ensureCapacity(ArrayList<Object> list, int capacity) {
84        int oldCapacity = capacity(list);
85        int oldModCount = modCount(list);
86        list.ensureCapacity(capacity);
87        assertTrue(capacity(list) >= capacity || capacity(list) == 0);
88        assertEquals(modCount(list),
89                     (capacity(list) == oldCapacity)
90                     ? oldModCount
91                     : oldModCount + 1);
92    }
93
94    static List<Object> singletonList() {
95        return Collections.singletonList(Boolean.TRUE);
96    }
97
98    /** Opportunistically randomly test various add operations. */
99    static void addOneElement(ArrayList<Object> list) {
100        int size = list.size();
101        int modCount = modCount(list);
102        switch (rnd.nextInt(4)) {
103        case 0: assertTrue(list.add(Boolean.TRUE)); break;
104        case 1: list.add(size, Boolean.TRUE); break;
105        case 2: assertTrue(list.addAll(singletonList())); break;
106        case 3: assertTrue(list.addAll(size, singletonList())); break;
107        default: throw new AssertionError();
108        }
109        assertEquals(modCount(list), modCount + 1);
110        assertEquals(list.size(), size + 1);
111    }
112
113    @Test public void defaultCapacity() {
114        ArrayList<Object> list = new ArrayList<>();
115        assertEquals(capacity(new ArrayList<Object>()), 0);
116        for (int i = 0; i < DEFAULT_CAPACITY; i++) {
117            addOneElement(list);
118            assertEquals(capacity(list), DEFAULT_CAPACITY);
119        }
120        addOneElement(list);
121        assertEquals(capacity(list), newCapacity(DEFAULT_CAPACITY));
122    }
123
124    @Test public void defaultCapacityEnsureCapacity() {
125        ArrayList<Object> list = new ArrayList<>();
126        for (int i = 0; i <= DEFAULT_CAPACITY; i++) {
127            ensureCapacity(list, i);     // no-op!
128            assertEquals(capacity(list), 0);
129        }
130        for (int i = 0; i < DEFAULT_CAPACITY; i++) {
131            addOneElement(list);
132            assertEquals(capacity(list), DEFAULT_CAPACITY);
133        }
134        addOneElement(list);
135        assertEquals(capacity(list), newCapacity(DEFAULT_CAPACITY));
136        {
137            int capacity = capacity(list);
138            ensureCapacity(list, capacity + 1);
139            assertEquals(capacity(list), newCapacity(capacity));
140        }
141        {
142            int capacity = capacity(list);
143            ensureCapacity(list, 3 * capacity);
144            assertEquals(capacity(list), 3 * capacity);
145        }
146    }
147
148    @Test public void ensureCapacityBeyondDefaultCapacity() {
149        ArrayList<Object> list = new ArrayList<>();
150        list.ensureCapacity(DEFAULT_CAPACITY + 1);
151        assertEquals(capacity(list), DEFAULT_CAPACITY + 1);
152        for (int i = 0; i < DEFAULT_CAPACITY + 1; i++) {
153            addOneElement(list);
154            assertEquals(capacity(list), DEFAULT_CAPACITY + 1);
155        }
156        addOneElement(list);
157        assertEquals(capacity(list), newCapacity(DEFAULT_CAPACITY + 1));
158    }
159
160    @Test public void explicitZeroCapacity() {
161        ArrayList<Object> list = new ArrayList<>(0);
162        assertEquals(capacity(list), 0);
163        addOneElement(list);
164        assertEquals(capacity(list), 1);
165        addOneElement(list);
166        assertEquals(capacity(list), 2);
167        addOneElement(list);
168        assertEquals(capacity(list), 3);
169        addOneElement(list);
170        assertEquals(capacity(list), 4);
171        addOneElement(list);
172        assertEquals(capacity(list), 6);
173        addOneElement(list);
174        assertEquals(capacity(list), 6);
175        addOneElement(list);
176        assertEquals(capacity(list), 9);
177        list.clear();
178        assertEquals(capacity(list), 9);
179    }
180
181    @Test public void explicitLargeCapacity() {
182        int n = DEFAULT_CAPACITY * 3;
183        ArrayList<Object> list = new ArrayList<>(n);
184        assertEquals(capacity(list), n);
185        ensureCapacity(list, 0);
186        ensureCapacity(list, n);
187        for (int i = 0; i < n; i++) addOneElement(list);
188        assertEquals(capacity(list), n);
189
190        addOneElement(list);
191        assertEquals(capacity(list), newCapacity(n));
192    }
193
194    @Test public void emptyArraysAreShared() {
195        assertSame(elementData(new ArrayList<Object>()),
196                   elementData(new ArrayList<Object>()));
197        assertSame(elementData(new ArrayList<Object>(0)),
198                   elementData(new ArrayList<Object>(0)));
199    }
200
201    @Test public void emptyArraysDifferBetweenDefaultAndExplicit() {
202        assertNotSame(elementData(new ArrayList<Object>()),
203                      elementData(new ArrayList<Object>(0)));
204    }
205
206    @Test public void negativeCapacity() {
207        for (int capacity : new int[] { -1, Integer.MIN_VALUE }) {
208            try {
209                new ArrayList<Object>(capacity);
210                fail("should throw");
211            } catch (IllegalArgumentException success) {}
212        }
213    }
214}
215