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/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Martin Buchholz with assistance from members of JCP
* JSR-166 Expert Group and released to the public domain, as
* explained at http://creativecommons.org/publicdomain/zero/1.0/
*/
/*
* @test
* @modules java.base/java.util:open
* @run testng WhiteBox
* @summary White box tests of implementation details
*/
import static org.testng.Assert.*;
import org.testng.annotations.Test;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.util.ArrayDeque;
import java.util.concurrent.ThreadLocalRandom;
@Test
public class WhiteBox {
final ThreadLocalRandom rnd = ThreadLocalRandom.current();
final VarHandle ELEMENTS, HEAD, TAIL;
WhiteBox() throws ReflectiveOperationException {
Class<?> klazz = ArrayDeque.class;
MethodHandles.Lookup lookup
= MethodHandles.privateLookupIn(klazz, MethodHandles.lookup());
ELEMENTS = lookup.findVarHandle(klazz, "elements", Object[].class);
HEAD = lookup.findVarHandle(klazz, "head", int.class);
TAIL = lookup.findVarHandle(klazz, "tail", int.class);
}
Object[] elements(ArrayDeque d) { return (Object[]) ELEMENTS.get(d); }
int head(ArrayDeque d) { return (int) HEAD.get(d); }
int tail(ArrayDeque d) { return (int) TAIL.get(d); }
void checkCapacity(ArrayDeque d, int capacity) {
assertTrue(d.isEmpty());
assertEquals(0, head(d));
assertEquals(0, tail(d));
Object[] initialElements = elements(d);
assertInvariants(d);
for (int i = capacity; i--> 0; ) {
d.add(rnd.nextInt(42));
assertSame(elements(d), initialElements);
assertInvariants(d);
}
d.add(rnd.nextInt(42));
assertNotSame(elements(d), initialElements);
assertInvariants(d);
}
@Test
public void defaultConstructor() {
checkCapacity(new ArrayDeque(), 16);
}
@Test
public void shouldNotResizeWhenInitialCapacityProvided() {
int initialCapacity = rnd.nextInt(20);
checkCapacity(new ArrayDeque(initialCapacity), initialCapacity);
}
byte[] serialBytes(Object o) {
try {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(o);
oos.flush();
oos.close();
return bos.toByteArray();
} catch (Exception fail) {
throw new AssertionError(fail);
}
}
@SuppressWarnings("unchecked")
<T> T serialClone(T o) {
try {
ObjectInputStream ois = new ObjectInputStream
(new ByteArrayInputStream(serialBytes(o)));
T clone = (T) ois.readObject();
assertNotSame(o, clone);
assertSame(o.getClass(), clone.getClass());
return clone;
} catch (Exception fail) {
throw new AssertionError(fail);
}
}
@Test
public void testSerialization() {
ArrayDeque[] ds = { new ArrayDeque(), new ArrayDeque(rnd.nextInt(20)) };
for (ArrayDeque d : ds) {
if (rnd.nextBoolean()) d.add(99);
ArrayDeque clone = serialClone(d);
assertInvariants(clone);
assertNotSame(elements(d), elements(clone));
assertEquals(d, clone);
}
}
/** Checks conditions which should always be true. */
void assertInvariants(ArrayDeque d) {
final Object[] elements = elements(d);
final int head = head(d);
final int tail = tail(d);
final int capacity = elements.length;
assertTrue(0 <= head && head < capacity);
assertTrue(0 <= tail && tail < capacity);
assertTrue(capacity > 0);
assertTrue(d.size() < capacity);
assertTrue((head == tail) ^ (elements[head] != null));
assertNull(elements[tail]);
assertTrue((head == tail) ^ (elements[Math.floorMod(tail - 1, capacity)] != null));
}
}
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