Add documention to NextPow2 function.

math/integer.go

@@ -2,11 +2,15 @@ package math
 
 import "math/bits"
 
-func NextPow2(n uint) (twoN uint, N uint) {
+// NextPow2 finds the next power of two (N=2^k, k>=0) greater than n.
+// If n is already a power of two, then this function returns n, and log2(n).
+func NextPow2(n uint) (N uint, k uint) {
 	if bits.OnesCount(n) == 1 {
-		return n, uint(bits.TrailingZeros(n))
+		k = uint(bits.TrailingZeros(n))
+		N = n
 	} else {
-		N = uint(bits.Len(n))
-		return uint(1) << N, N
+		k = uint(bits.Len(n))
+		N = uint(1) << k
 	}
+	return
 }