Fixed a bug int the new version of Long.reverse introduce in change Id6bd7c81.

The corresponding code in Hacker's Delight is written in C, which supports
unsigned numbers. In Java, it's essential to use explicit unsigned shifts,
but I neglected to do so.  This bug was caught by jtreg test
java.lang.Long.BitTwiddle (which I wrote in 2003).  This preexisting
test serves as the regression test for this change.

diff --git a/libcore/luni/src/main/java/java/lang/Long.java b/libcore/luni/src/main/java/java/lang/Long.java
index 8a2a8da..1b28a5a 100644 (file)
--- a/libcore/luni/src/main/java/java/lang/Long.java
+++ b/libcore/luni/src/main/java/java/lang/Long.java
@@ -531,7 +531,7 @@ public final class Long extends Number implements Comparable<Long> {
             buf[--cursor] = (char) (midDigit + '0');
 
             // Exact division as per Warren 10-20
-            int rest = ((int) ((n - midDigit) >> 1)) * 0xCCCCCCCD;
+            int rest = ((int) ((n - midDigit) >>> 1)) * 0xCCCCCCCD;
             cursor = intIntoCharArray(buf, cursor, rest);
         }
 
@@ -740,19 +740,19 @@ public final class Long extends Number implements Comparable<Long> {
             n +=  32;
             i = (int) v;
         }
-        if (i >> 16 == 0) {
+        if (i >>> 16 == 0) {
             n +=  16;
             i <<= 16;
         }
-        if (i >> 24 == 0) {
+        if (i >>> 24 == 0) {
             n +=  8;
             i <<= 8;
         }
-        if (i >> 28 == 0) {
+        if (i >>> 28 == 0) {
             n +=  4;
             i <<= 4;
         }
-        if (i >> 30 == 0) {
+        if (i >>> 30 == 0) {
             n +=  2;
             i <<= 2;
         }
@@ -786,9 +786,9 @@ public final class Long extends Number implements Comparable<Long> {
     public static int bitCount(long v) {
         // Combines techniques from several sources
         v -=  (v >>> 1) & 0x5555555555555555L;
-        v = (v & 0x3333333333333333L) + ((v >> 2) & 0x3333333333333333L);
+        v = (v & 0x3333333333333333L) + ((v >>> 2) & 0x3333333333333333L);
         int i =  ((int)(v >>> 32)) + (int) v;
-        i = (i & 0x0F0F0F0F) + ((i >> 4) & 0x0F0F0F0F);
+        i = (i & 0x0F0F0F0F) + ((i >>> 4) & 0x0F0F0F0F);
         i += i >>> 8;
         i += i >>> 16;
         return i  & 0x0000007F;
@@ -854,9 +854,9 @@ public final class Long extends Number implements Comparable<Long> {
     public static long reverseBytes(long v) {
         // Hacker's Delight 7-1, with minor tweak from Veldmeijer
         // http://graphics.stanford.edu/~seander/bithacks.html
-        v = ((v >> 8) & 0x00FF00FF00FF00FFL) | ((v & 0x00FF00FF00FF00FFL) << 8);
-        v = ((v >>16) & 0x0000FFFF0000FFFFL) | ((v & 0x0000FFFF0000FFFFL) <<16);
-        return ((v >>32)                   ) | ((v                      ) <<32);
+        v = ((v >>> 8) & 0x00FF00FF00FF00FFL) | ((v & 0x00FF00FF00FF00FFL) << 8);
+        v = ((v >>>16) & 0x0000FFFF0000FFFFL) | ((v & 0x0000FFFF0000FFFFL) <<16);
+        return ((v >>>32)                   ) | ((v                      ) <<32);
     }
 
     /**
@@ -870,12 +870,12 @@ public final class Long extends Number implements Comparable<Long> {
     public static long reverse(long v) {
         // Hacker's Delight 7-1, with minor tweak from Veldmeijer
         // http://graphics.stanford.edu/~seander/bithacks.html
-        v = ((v >> 1) & 0x5555555555555555L) | ((v & 0x5555555555555555L) << 1);
-        v = ((v >> 2) & 0x3333333333333333L) | ((v & 0x3333333333333333L) << 2);
-        v = ((v >> 4) & 0x0F0F0F0F0F0F0F0FL) | ((v & 0x0F0F0F0F0F0F0F0FL) << 4);
-        v = ((v >> 8) & 0x00FF00FF00FF00FFL) | ((v & 0x00FF00FF00FF00FFL) << 8);
-        v = ((v >>16) & 0x0000FFFF0000FFFFL) | ((v & 0x0000FFFF0000FFFFL) <<16);
-        return ((v >>32)                   ) | ((v                      ) <<32);
+        v = ((v >>> 1) & 0x5555555555555555L) | ((v & 0x5555555555555555L) << 1);
+        v = ((v >>> 2) & 0x3333333333333333L) | ((v & 0x3333333333333333L) << 2);
+        v = ((v >>> 4) & 0x0F0F0F0F0F0F0F0FL) | ((v & 0x0F0F0F0F0F0F0F0FL) << 4);
+        v = ((v >>> 8) & 0x00FF00FF00FF00FFL) | ((v & 0x00FF00FF00FF00FFL) << 8);
+        v = ((v >>>16) & 0x0000FFFF0000FFFFL) | ((v & 0x0000FFFF0000FFFFL) <<16);
+        return ((v >>>32)                   ) | ((v                      ) <<32);
     }
 
     /**