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Merge "Gracefully handle integer overflows." am: cdb1f03144

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Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1316217

Change-Id: I779298886cfaef330b433fea6009860682df35bd
This commit is contained in:
Junyu Lai
2020-07-29 01:37:48 +00:00
committed by Automerger Merge Worker
parent ef723b7617 cdb1f03144
commit fe6c5793ce
2 changed files with 47 additions and 13 deletions
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31
core/java/android/net/NetworkUtils.java
View File

@@ -476,4 +476,35 @@ public class NetworkUtils {
return true;
}
/**
* Safely multiple a value by a rational.
* <p>
* Internally it uses integer-based math whenever possible, but switches
* over to double-based math if values would overflow.
* @hide
*/
public static long multiplySafeByRational(long value, long num, long den) {
if (den == 0) {
throw new ArithmeticException("Invalid Denominator");
}
long x = value;
long y = num;
// Logic shamelessly borrowed from Math.multiplyExact()
long r = x * y;
long ax = Math.abs(x);
long ay = Math.abs(y);
if (((ax | ay) >>> 31 != 0)) {
// Some bits greater than 2^31 that might cause overflow
// Check the result using the divide operator
// and check for the special case of Long.MIN_VALUE * -1
if (((y != 0) && (r / y != x)) ||
(x == Long.MIN_VALUE && y == -1)) {
// Use double math to avoid overflowing
return (long) (((double) num / den) * value);
}
}
return r / den;
}
}

29
tests/net/java/com/android/server/net/NetworkStatsCollectionTest.java
View File

@@ -23,11 +23,12 @@ import static android.net.NetworkStats.TAG_NONE;
import static android.net.NetworkStats.UID_ALL;
import static android.net.NetworkStatsHistory.FIELD_ALL;
import static android.net.NetworkTemplate.buildTemplateMobileAll;
import static android.net.NetworkUtils.multiplySafeByRational;
import static android.os.Process.myUid;
import static android.text.format.DateUtils.HOUR_IN_MILLIS;
import static android.text.format.DateUtils.MINUTE_IN_MILLIS;
import static com.android.server.net.NetworkStatsCollection.multiplySafe;
import static com.android.testutils.MiscAssertsKt.assertThrows;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
@@ -505,23 +506,25 @@ public class NetworkStatsCollectionTest {
}
@Test
public void testMultiplySafe() {
assertEquals(25, multiplySafe(50, 1, 2));
assertEquals(100, multiplySafe(50, 2, 1));
public void testMultiplySafeRational() {
assertEquals(25, multiplySafeByRational(50, 1, 2));
assertEquals(100, multiplySafeByRational(50, 2, 1));
assertEquals(-10, multiplySafe(30, -1, 3));
assertEquals(0, multiplySafe(30, 0, 3));
assertEquals(10, multiplySafe(30, 1, 3));
assertEquals(20, multiplySafe(30, 2, 3));
assertEquals(30, multiplySafe(30, 3, 3));
assertEquals(40, multiplySafe(30, 4, 3));
assertEquals(-10, multiplySafeByRational(30, -1, 3));
assertEquals(0, multiplySafeByRational(30, 0, 3));
assertEquals(10, multiplySafeByRational(30, 1, 3));
assertEquals(20, multiplySafeByRational(30, 2, 3));
assertEquals(30, multiplySafeByRational(30, 3, 3));
assertEquals(40, multiplySafeByRational(30, 4, 3));
assertEquals(100_000_000_000L,
multiplySafe(300_000_000_000L, 10_000_000_000L, 30_000_000_000L));
multiplySafeByRational(300_000_000_000L, 10_000_000_000L, 30_000_000_000L));
assertEquals(100_000_000_010L,
multiplySafe(300_000_000_000L, 10_000_000_001L, 30_000_000_000L));
multiplySafeByRational(300_000_000_000L, 10_000_000_001L, 30_000_000_000L));
assertEquals(823_202_048L,
multiplySafe(4_939_212_288L, 2_121_815_528L, 12_730_893_165L));
multiplySafeByRational(4_939_212_288L, 2_121_815_528L, 12_730_893_165L));
assertThrows(ArithmeticException.class, () -> multiplySafeByRational(30, 3, 0));
}
/**