Lua中的中文字符串（UTF-8）處理（獲取長度、截取字符串）

function LuaHelps.GetCharSize(char)--獲取單個字符長度
	if not char then
		return 0
	elseif char > 240 then
		return 4
	elseif char > 225 then
		return 3
	elseif char > 192 then
		return 2
	else
		return 1
	end
end

function LuaHelps.GetUtf8Len(str)--獲取中文字符長度
	local len = 0 
	local currentIndex = 1 
	while currentIndex <= #str do 
		local char = string.byte(str,currentIndex) 
		currentIndex = currentIndex + LuaHelps.GetCharSize(char) 
		len = len + 1 
	end 
	return len 
end

function LuaHelps.StrUtf8Sub(str, startChar, numChars)--截取中文字符串
	local startIndex = 1 
	while startChar > 1 do 
		local char = string.byte(str,startIndex) 
		startIndex = startIndex + LuaHelps.GetCharSize(char) 
		startChar = startChar - 1 
	end
	
	local currentIndex = startIndex
	
	while numChars > 0 and currentIndex <= #str do
		local char = string.byte(str,currentIndex)
		currentIndex = currentIndex + LuaHelps.GetCharSize(char)
		numChars = numChars - 1
	end
	
	return string.sub(str, startIndex, currentIndex-1)
end

參考博文：https://www.cnblogs.com/slysky/p/6098981.html