Changed hashing bit rotation to use Integer.rotateRight

l0rinc · l0rinc · commit bc912230129d · 2016-12-07T13:38:02.000+02:00
diff --git a/src/library/scala/collection/mutable/FlatHashTable.scala b/src/library/scala/collection/mutable/FlatHashTable.scala
@@ -10,6 +10,9 @@ package scala
 package collection
 package mutable
 
+import java.lang.Integer.rotateRight
+import scala.util.hashing.byteswap32
+
 /** An implementation class backing a `HashSet`.
  *
  *  This trait is used internally. It can be mixed in with various collections relying on
@@ -415,20 +418,7 @@ private[collection] object FlatHashTable {
     // so that:
     protected final def sizeMapBucketSize = 1 << sizeMapBucketBitSize
 
-    protected final def improve(hcode: Int, seed: Int) = {
-      //var h: Int = hcode + ~(hcode << 9)
-      //h = h ^ (h >>> 14)
-      //h = h + (h << 4)
-      //h ^ (h >>> 10)
-
-      val improved= scala.util.hashing.byteswap32(hcode)
-
-      // for the remainder, see SI-5293
-      // to ensure that different bits are used for different hash tables, we have to rotate based on the seed
-      val rotation = seed % 32
-      val rotated = (improved >>> rotation) | (improved << (32 - rotation))
-      rotated
-    }
+    protected final def improve(hcode: Int, seed: Int) = rotateRight(byteswap32(hcode), seed)
 
     /**
      * Elems have type A, but we store AnyRef in the table. Plus we need to deal with
diff --git a/src/library/scala/collection/mutable/HashTable.scala b/src/library/scala/collection/mutable/HashTable.scala
@@ -12,6 +12,9 @@ package scala
 package collection
 package mutable
 
+import java.lang.Integer.rotateRight
+import scala.util.hashing.byteswap32
+
 /** This class can be used to construct data structures that are based
  *  on hashtables. Class `HashTable[A]` implements a hashtable
  *  that maps keys of type `A` to values of the fully abstract
@@ -424,11 +427,7 @@ private[collection] object HashTable {
       * }}}
       * the rest of the computation is due to SI-5293
       */
-    protected final def improve(hcode: Int, seed: Int): Int = {
-      val hash = scala.util.hashing.byteswap32(hcode)
-      val shift = seed & ((1 << 5) - 1)
-      (hash >>> shift) | (hash << (32 - shift))
-    }
+    protected final def improve(hcode: Int, seed: Int): Int = rotateRight(byteswap32(hcode), seed)
   }
 
   /**
