Hello.
Please review this simple improvement in handling an exceptional
condition in BigInteger. A stack overflow on an argument of
BigInteger.shitf{Left, Right}(Integer.MIN_VALUE) is handled as an
explicit ArithmeticException, the same exception used throughout
BigInteger for other invalid inputs.
Patch below; webrev at
http://cr.openjdk.java.net/~darcy/6371401.0/
Thanks,
-Joe
--- old/src/share/classes/java/math/BigInteger.java 2009-10-19
17:37:36.000000000 -0700
+++ new/src/share/classes/java/math/BigInteger.java 2009-10-19
17:37:35.000000000 -0700
@@ -2051,6 +2051,8 @@
*
* @param n shift distance, in bits.
* @return {...@code this << n}
+ * @throws ArithmeticException if the shift distance is {...@code
+ * Integer.MIN_VALUE}.
* @see #shiftRight
*/
public BigInteger shiftLeft(int n) {
@@ -2058,8 +2060,13 @@
return ZERO;
if (n==0)
return this;
- if (n<0)
- return shiftRight(-n);
+ if (n<0) {
+ if (n == Integer.MIN_VALUE) {
+ throw new ArithmeticException("Shift distance of
Integer.MIN_VALUE not supported.");
+ } else {
+ return shiftRight(-n);
+ }
+ }
int nInts = n >>> 5;
int nBits = n & 0x1f;
@@ -2097,13 +2104,20 @@
*
* @param n shift distance, in bits.
* @return {...@code this >> n}
+ * @throws ArithmeticException if the shift distance is {...@code
+ * Integer.MIN_VALUE}.
* @see #shiftLeft
*/
public BigInteger shiftRight(int n) {
if (n==0)
return this;
- if (n<0)
- return shiftLeft(-n);
+ if (n<0) {
+ if (n == Integer.MIN_VALUE) {
+ throw new ArithmeticException("Shift distance of
Integer.MIN_VALUE not supported.");
+ } else {
+ return shiftLeft(-n);
+ }
+ }
int nInts = n >>> 5;
int nBits = n & 0x1f;
--- /dev/null 2009-07-06 20:02:10.000000000 -0700
+++ new/test/java/math/BigInteger/ExtremeShiftingTests.java
2009-10-19 17:37:36.000000000 -0700
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * @test
+ * @bug 6371401
+ * @summary Tests of shiftLeft and shiftRight on Integer.MIN_VALUE
+ * @author Joseph D. Darcy
+ */
+import java.math.*;
+import static java.math.BigInteger.*;
+
+public class ExtremeShiftingTests {
+ public static void main(String... args) {
+ try {
+ ONE.shiftLeft(Integer.MIN_VALUE);
+ throw new RuntimeException("Should not reach here.");
+ } catch (ArithmeticException ae) {
+ ; // Expected
+ }
+
+ try {
+ ONE.shiftRight(Integer.MIN_VALUE);
+ throw new RuntimeException("Should not reach here.");
+ } catch (ArithmeticException ae) {
+ ; // Expected
+ }
+ }
+}
