Lua获取utf8字符串长度和字符串截取并用...代替

--- 获取utf8编码字符串正确长度的方法
-- @param str
-- @return number
function utfstrlen(str)
local len = #str;
local left = len;
local cnt = 0;
local arr={0,0xc0,0xe0,0xf0,0xf8,0xfc};
while left ~= 0 do
local tmp=string.byte(str,-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

--@brief 切割字符串，并用“...”替换尾部
--@param sName:要切割的字符串
--@return nMaxCount，字符串上限,中文字为2的倍数
--@param nShowCount：显示英文字个数，中文字为2的倍数,可为空
--@note         函数实现：截取字符串一部分，剩余用“...”替换

function GetShortName(sName,nMaxCount,nShowCount)
    if sName == nil or nMaxCount == nil then
        return
    end
    local sStr = sName
    local tCode = {}
    local tName = {}
    local nLenInByte = #sStr
    local nWidth = 0
    if nShowCount == nil then
       nShowCount = nMaxCount - 3
    end
    for i=1,nLenInByte do
        local curByte = string.byte(sStr, i)
        local byteCount = 0;
        if curByte>0 and curByte=127 then
            byteCount = 1
        elseif curByte>=192 and curByte223 then
            byteCount = 2
        elseif curByte>=224 and curByte239 then
            byteCount = 3
        elseif curByte>=240 and curByte=247 then
            byteCount = 4
        end
        local char = nil
        if byteCount > 0 then
            char = string.sub(sStr, i, i+byteCount-1)
            i = i + byteCount -1
        end
        if byteCount == 1 then
            nWidth = nWidth + 1
            table.insert(tName,char)
            table.insert(tCode,1)
           
        elseif byteCount > 1 then
            nWidth = nWidth + 2
            table.insert(tName,char)
            table.insert(tCode,2)
        end
    end
   
    if nWidth > nMaxCount then
        local _sN = ""
        local _len = 0
        for i=1,#tName do
            _sN = _sN .. tName[i]
            _len = _len + tCode[i]
            if _len >= nShowCount then
                break
            end
        end
        sName = _sN .. "..."
    end
    return sName
end