diff --git a/Zframework/toolfunc.lua b/Zframework/toolfunc.lua
index 581e8582..b41a25c3 100644
--- a/Zframework/toolfunc.lua
+++ b/Zframework/toolfunc.lua
@@ -332,17 +332,15 @@ do--json
 
 	local function codepoint_to_utf8(n)
 		-- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
-		local f = math.floor
+		local f = bit.rshift
 		if n <= 0x7f then
 			return char(n)
 		elseif n <= 0x7ff then
-			return char(f(n / 64) + 192, n % 64 + 128)
+			return char(f(n, 6) + 192, n % 64 + 128)
 		elseif n <= 0xffff then
-			return char(f(n / 4096) + 224, f(n % 4096 / 64) + 128,
-							n % 64 + 128)
+			return char(f(n, 12) + 224, f(n % 4096, 6) + 128, n % 64 + 128)
 		elseif n <= 0x10ffff then
-			return char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
-							f(n % 4096 / 64) + 128, n % 64 + 128)
+			return char(f(n, 18) + 240, f(n % 262144, 12) + 128, f(n % 4096, 6) + 128, n % 64 + 128)
 		end
 		error(string.format("invalid unicode codepoint '%x'", n))
 	end