Use Java's highestOneBit, rather than our own versions.

The original code came from 2008, (a4ace382), at which point
we probably couldn't use JDK 1.5+ methods.

I haven't changed `unsignedCompare` yet to use the standard
library version, as it our version might have different
performance characteristics.

Background: http://www.drmaciver.com/2008/08/unsigned-comparison-in-javascala/

1 files changed, 2 insertions, 21 deletions

diff --git a/src/library/scala/collection/generic/BitOperations.scala b/src/library/scala/collection/generic/BitOperations.scala
index d430ece2f5..2f460eee1f 100644
--- a/src/library/scala/collection/generic/BitOperations.scala
+++ b/src/library/scala/collection/generic/BitOperations.scala
@@ -26,16 +26,7 @@ private[collection] object BitOperations {
     def complement(i: Int)                      = (-1) ^ i
     def bits(num: Int)                          = 31 to 0 by -1 map (i => (num >>> i & 1) != 0)
     def bitString(num: Int, sep: String = "")   = bits(num) map (b => if (b) "1" else "0") mkString sep
-
-    def highestOneBit(j: Int) = {
-      var i = j
-      i |= (i >>  1)
-      i |= (i >>  2)
-      i |= (i >>  4)
-      i |= (i >>  8)
-      i |= (i >> 16)
-      i - (i >>> 1)
-    }
+    def highestOneBit(j: Int)                   = java.lang.Integer.highestOneBit(j)
   }
   object Int extends Int
 
@@ -49,17 +40,7 @@ private[collection] object BitOperations {
     def complement(i: Long)                        = (-1L) ^ i
     def bits(num: Long)                            = 63L to 0L by -1L map (i => (num >>> i & 1L) != 0L)
     def bitString(num: Long, sep: String = "")     = bits(num) map (b => if (b) "1" else "0") mkString sep
-
-    def highestOneBit(j: Long) = {
-      var i = j
-      i |= (i >>  1)
-      i |= (i >>  2)
-      i |= (i >>  4)
-      i |= (i >>  8)
-      i |= (i >> 16)
-      i |= (i >> 32)
-      i - (i >>> 1)
-    }
+    def highestOneBit(j: Long)                     = java.lang.Long.highestOneBit(j)
   }
   object Long extends Long
 }