pool: support CountMany() using hyperloglog.

nip45/hyperloglog/helpers.go

@@ -0,0 +1,30 @@
+package hyperloglog
+
+import (
+	"math"
+)
+
+const two32 = 1 << 32
+
+func linearCounting(m uint32, v uint32) float64 {
+	fm := float64(m)
+	return fm * math.Log(fm/float64(v))
+}
+
+func clz56(x uint64) uint8 {
+	var c uint8
+	for m := uint64(1 << 55); m&x == 0 && m != 0; m >>= 1 {
+		c++
+	}
+	return c
+}
+
+func countZeros(s []uint8) uint32 {
+	var c uint32
+	for _, v := range s {
+		if v == 0 {
+			c++
+		}
+	}
+	return c
+}