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8294509: The sign extension bug applies to 'public static int[] convertSeedBytesToInts(byte[] seed, int n, int z)' in RandomSupport

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Reviewed-by: shade
This commit is contained in:
Raffaello Giulietti 2022-10-04 10:25:11 +00:00
parent f03934e270
commit 5a9cd33632
2 changed files with 41 additions and 2 deletions
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2
src/java.base/share/classes/jdk/internal/util/random/RandomSupport.java
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@ -312,7 +312,7 @@ public class RandomSupport {
final int m = Math.min(seed.length, n << 2);
// Distribute seed bytes into the words to be formed.
for (int j = 0; j < m; j++) {
result[j>>2] = (result[j>>2] << 8) | seed[j];
result[j>>2] = (result[j>>2] << 8) | (seed[j] & 0xFF);
}
// If there aren't enough seed bytes for all the words we need,
// use a SplitMix-style PRNG to fill in the rest.

41
test/jdk/java/util/Random/T8282144.java
View File

@ -27,7 +27,7 @@ import jdk.internal.util.random.RandomSupport;
/**
* @test
* @summary RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes.
* @bug 8282144
* @bug 8282144 8294509
* @modules java.base/jdk.internal.util.random
* @run main T8282144
* @key randomness
@ -36,6 +36,11 @@ import jdk.internal.util.random.RandomSupport;
public class T8282144 {
public static void main(String[] args) {
testLongs();
testInts();
}
private static void testLongs() {
RandomGenerator rng = RandomGeneratorFactory.of("L64X128MixRandom").create(42);
for (int i = 1; i < 8; i++) {
@ -56,6 +61,27 @@ public class T8282144 {
}
}
private static void testInts() {
RandomGenerator rng = RandomGeneratorFactory.of("L64X128MixRandom").create(42);
for (int i = 1; i < 8; i++) {
byte[] seed = new byte[i];
for (int j = 0; j < 10; j++) {
rng.nextBytes(seed);
int[] existing = RandomSupport.convertSeedBytesToInts(seed, 1, 1);
int[] testing = convertSeedBytesToIntsFixed(seed, 1, 1);
for (int k = 0; k < existing.length; k++) {
if (existing[k] != testing[k]) {
throw new RuntimeException("convertSeedBytesToInts incorrect");
}
}
}
}
}
public static long[] convertSeedBytesToLongsFixed(byte[] seed, int n, int z) {
final long[] result = new long[n];
@ -68,4 +94,17 @@ public class T8282144 {
return result;
}
public static int[] convertSeedBytesToIntsFixed(byte[] seed, int n, int z) {
final int[] result = new int[n];
final int m = Math.min(seed.length, n << 2);
// Distribute seed bytes into the words to be formed.
for (int j = 0; j < m; j++) {
result[j >> 2] = (result[j >> 2] << 8) | (seed[j] & 0xff);
}
return result;
}
}