Merge pull request #89530 from tklauser/use-bits-onescount

Use OnesCount8 from math/bits to implement countBits

pkg/registry/core/service/allocator/utils.go

@@ -16,49 +16,16 @@ limitations under the License.
 
 package allocator
 
-import "math/big"
+import (
+	"math/big"
+	"math/bits"
+)
 
 // countBits returns the number of set bits in n
 func countBits(n *big.Int) int {
 	var count int = 0
 	for _, b := range n.Bytes() {
-		count += int(bitCounts[b])
+		count += bits.OnesCount8(uint8(b))
 	}
 	return count
 }
-
-// bitCounts is all of the bits counted for each number between 0-255
-var bitCounts = []int8{
-	0, 1, 1, 2, 1, 2, 2, 3,
-	1, 2, 2, 3, 2, 3, 3, 4,
-	1, 2, 2, 3, 2, 3, 3, 4,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	1, 2, 2, 3, 2, 3, 3, 4,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	1, 2, 2, 3, 2, 3, 3, 4,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	4, 5, 5, 6, 5, 6, 6, 7,
-	1, 2, 2, 3, 2, 3, 3, 4,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	4, 5, 5, 6, 5, 6, 6, 7,
-	2, 3, 3, 4, 3, 4, 4, 5,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	4, 5, 5, 6, 5, 6, 6, 7,
-	3, 4, 4, 5, 4, 5, 5, 6,
-	4, 5, 5, 6, 5, 6, 6, 7,
-	4, 5, 5, 6, 5, 6, 6, 7,
-	5, 6, 6, 7, 6, 7, 7, 8,
-}

pkg/registry/core/service/allocator/utils_test.go

@@ -21,20 +21,6 @@ import (
 	"testing"
 )
 
-func TestBitCount(t *testing.T) {
-	for i, c := range bitCounts {
-		actual := 0
-		for j := 0; j < 8; j++ {
-			if ((1 << uint(j)) & i) != 0 {
-				actual++
-			}
-		}
-		if actual != int(c) {
-			t.Errorf("%d should have %d bits but recorded as %d", i, actual, c)
-		}
-	}
-}
-
 func TestCountBits(t *testing.T) {
 	tests := []struct {
 		n        *big.Int