function string.utf8len(input)
local len = string.len(input)
local left = len
local cnt = 0
local arr = {0, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc}
while left ~= 0 do
local tmp = string.byte(input, -left)
local i = #arr
while arr[i] do
if tmp >= arr[i] then
left = left - i
break
end
i = i - 1
end
cnt = cnt + 1
end
return cnt
end
