feat: Inital commit

vendor/github.com/bits-and-blooms/bitset/select.go

@@ -0,0 +1,47 @@
+package bitset
+
+import "math/bits"
+
+func select64(w uint64, j uint) uint {
+	seen := 0
+	// Divide 64bit
+	part := w & 0xFFFFFFFF
+	n := uint(bits.OnesCount64(part))
+	if n <= j {
+		part = w >> 32
+		seen += 32
+		j -= n
+	}
+	ww := part
+
+	// Divide 32bit
+	part = ww & 0xFFFF
+
+	n = uint(bits.OnesCount64(part))
+	if n <= j {
+		part = ww >> 16
+		seen += 16
+		j -= n
+	}
+	ww = part
+
+	// Divide 16bit
+	part = ww & 0xFF
+	n = uint(bits.OnesCount64(part))
+	if n <= j {
+		part = ww >> 8
+		seen += 8
+		j -= n
+	}
+	ww = part
+
+	// Lookup in final byte
+	counter := 0
+	for ; counter < 8; counter++ {
+		j -= uint((ww >> counter) & 1)
+		if j+1 == 0 {
+			break
+		}
+	}
+	return uint(seen + counter)
+}