uses math/bits for trailing zeros

bitset.go

@@ -305,17 +305,6 @@ func (b *BitSet) Count() uint {
 	return 0
 }
 
-var deBruijn = [...]byte{
-	0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4,
-	62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5,
-	63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11,
-	54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6,
-}
-
-func trailingZeroes64(v uint64) uint {
-	return uint(deBruijn[((v&-v)*0x03f79d71b4ca8b09)>>58])
-}
-
 // Equal tests the equvalence of two BitSets.
 // False if they are of different sizes, otherwise true
 // only if all the same bits are set

trailing_zeros_18.go

@@ -0,0 +1,14 @@
+// +build !go1.9
+
+package bitset
+
+var deBruijn = [...]byte{
+	0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4,
+	62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5,
+	63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11,
+	54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6,
+}
+
+func trailingZeroes64(v uint64) uint {
+	return uint(deBruijn[((v&-v)*0x03f79d71b4ca8b09)>>58])
+}

trailing_zeros_19.go

@@ -0,0 +1,9 @@
+// +build go1.9
+
+package bitset
+
+import "math/bits"
+
+func trailingZeroes64(v uint64) uint {
+	return uint(bits.TrailingZeros64(v))
+}