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/*
* Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
* 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.
*/
import jdk.test.lib.RandomFactory;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import java.math.Accessor;
import java.math.BigInteger;
import java.util.Random;
import static org.junit.jupiter.api.Assertions.assertTrue;
/**
* @test
* @bug 8319174
* @summary Exercises minimality of BigInteger.mag field (use -Dseed=X to set PRANDOM seed)
* @library /test/lib
* @build jdk.test.lib.RandomFactory
* @build java.base/java.math.Accessor
* @key randomness
* @run junit/othervm -DmaxDurationMillis=3000 ByteArrayConstructorTest
*/
public class ByteArrayConstructorTest {
private static final int DEFAULT_MAX_DURATION_MILLIS = 3_000;
public static final int N = 1_024;
private static int maxDurationMillis;
private static final Random rnd = RandomFactory.getRandom();
private volatile boolean stop = false;
@BeforeAll
static void setMaxDurationMillis() {
maxDurationMillis = Math.max(maxDurationMillis(), 0);
}
@Test
public void testNonNegative() throws InterruptedException {
byte[] ba = nonNegativeBytes();
doBigIntegers(ba, ba[0]); // a mask to flip to 0 and back to ba[0]
}
@Test
public void testNegative() throws InterruptedException {
byte[] ba = negativeBytes();
doBigIntegers(ba, (byte) ~ba[0]); // a mask to flip to -1 and back to ba[0]
}
/*
* Starts a thread th that keeps flipping the "sign" byte in the array ba
* from the original value to 0 or -1 and back, depending on ba[0] being
* non-negative or negative, resp.
* (ba is "big endian", the least significant byte is the one with the
* highest index.)
*
* In the meantime, the current thread keeps creating BigInteger instances
* with ba and checks that the internal invariant holds, despite the
* attempts by thread th to racily modify ba.
* It does so at least as indicated by maxDurationMillis.
*
* Finally, this thread requests th to stop and joins with it, either
* because maxDurationMillis has expired, or because of an invalid invariant.
*/
private void doBigIntegers(byte[] ba, byte mask) throws InterruptedException {
Thread th = new Thread(() -> {
while (!stop) {
ba[0] ^= mask;
}
});
th.start();
try {
createBigIntegers(maxDurationMillis, ba);
} finally {
stop = true;
th.join(1_000);
}
}
private void createBigIntegers(int maxDurationMillis, byte[] ba) {
long start = System.currentTimeMillis();
while (System.currentTimeMillis() - start < maxDurationMillis) {
BigInteger bi = new BigInteger(ba);
int[] mag = Accessor.mag(bi);
assertTrue(mag.length == 0 || mag[0] != 0,
String.format("inconsistent BigInteger: mag.length=%d, mag[0]=%d",
mag.length, mag[0]));
}
}
private byte[] nonNegativeBytes() {
byte[] ba = new byte[1 + N];
byte b0;
while ((b0 = (byte) rnd.nextInt()) < 0); // empty body
rnd.nextBytes(ba);
ba[0] = b0;
/* Except for ba[0], fill most significant half with zeros. */
for (int i = 1; i <= N / 2; ++i) {
ba[i] = 0;
}
return ba;
}
private byte[] negativeBytes() {
byte[] ba = new byte[1 + N];
byte b0;
while ((b0 = (byte) rnd.nextInt()) >= 0); // empty body
rnd.nextBytes(ba);
ba[0] = b0;
/* Except for ba[0], fill most significant half with -1 bytes. */
for (int i = 1; i <= N / 2; ++i) {
ba[i] = -1;
}
return ba;
}
private static int maxDurationMillis() {
try {
return Integer.parseInt(System.getProperty("maxDurationMillis",
Integer.toString(DEFAULT_MAX_DURATION_MILLIS)));
} catch (NumberFormatException ignore) {
}
return DEFAULT_MAX_DURATION_MILLIS;
}
}
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