Fixes issue 3569.  LongLib.shr gave incorrect results
when the shift amount was greater than 32.  This revision adds
two new test cases and modifies LongLib.shr to handle them.

Review by: fabbott


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@5270 8db76d5a-ed1c-0410-87a9-c151d255dfc7

dev/core/super/com/google/gwt/lang/LongLib.java

diff --git a/dev/core/super/com/google/gwt/lang/LongLib.java b/dev/core/super/com/google/gwt/lang/LongLib.java
index db43c0f..9226113 100644
--- a/dev/core/super/com/google/gwt/lang/LongLib.java
+++ b/dev/core/super/com/google/gwt/lang/LongLib.java
@@ -394,8 +394,17 @@
   public static double[] shr(double[] a, int n) {
     n &= 63;
     double shiftFact = pwrAsDouble(n);
-    double newHigh = a[HIGH] / shiftFact;
+    double newHigh = Math.floor(a[HIGH] / shiftFact);
     double newLow = Math.floor(a[LOW] / shiftFact);
+
+    /*
+     * Doing the above floors separately on each component is safe. If n<32,
+     * a[HIGH]/shiftFact is guaranteed to be an integer already. For n>32,
+     * a[HIGH]/shiftFact will have fractional bits, but we need to discard them
+     * as they shift away. We will end up discarding all of a[LOW] in this case,
+     * as it divides out to entirely fractional.
+     */
+
     return create(newLow, newHigh);
   }
 

dev/core/test/com/google/gwt/lang/LongLibTestBase.java

diff --git a/dev/core/test/com/google/gwt/lang/LongLibTestBase.java b/dev/core/test/com/google/gwt/lang/LongLibTestBase.java
index 2766669..bd0f38d 100644
--- a/dev/core/test/com/google/gwt/lang/LongLibTestBase.java
+++ b/dev/core/test/com/google/gwt/lang/LongLibTestBase.java
@@ -272,10 +272,13 @@
         longFromBits(0x92341234, 0x45674567), 10));
     assertEquals(longFromBits(0xffe48d04, 0x8d1159d1), LongLib.shr(
         longFromBits(0x92341234, 0x45674567), 10));
+    assertEquals(LongLib.fromInt(67108863), LongLib.shr(longFromBits(0xFFFFFFF,
+        0xFFFFFFFF), 34));
     assertEquals(longFromBits(0x248d04, 0x8d1159d1), LongLib.shru(longFromBits(
         0x92341234, 0x45674567), 10));
 
     assertEquals(LongLib.fromInt(-1), LongLib.shr(LongLib.fromInt(-1), 10));
+    assertEquals(LongLib.fromInt(-1), LongLib.shr(LongLib.fromInt(-1), 63));
 
     assertEquals(LongLib.fromInt(-1 << 5), LongLib.shl(LongLib.fromInt(-1), 5));
     assertEquals(LongLib.fromInt(-1), LongLib.shl(LongLib.fromInt(-1), 0));