local function encodeBase64(source_str)    local b64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'    local s64 = ''    local str = source_str    while #str > 0 do        local bytes_num = 0        local buf = 0        for byte_cnt=1,3 do            buf = (buf * 256)            if #str > 0 then                buf = buf + string.byte(str, 1, 1)                str = string.sub(str, 2)                bytes_num = bytes_num + 1            end        end        for group_cnt=1,(bytes_num+1) do            local b64char = math.fmod(math.floor(buf/262144), 64) + 1            s64 = s64 .. string.sub(b64chars, b64char, b64char)            buf = buf * 64        end        for fill_cnt=1,(3-bytes_num) do            s64 = s64 .. '='        end    end    return s64endlocal function decodeBase64(str64)    local b64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'    local temp={}    for i=1,64 do        temp[string.sub(b64chars,i,i)] = i    end    temp['=']=0    local str=""    for i=1,#str64,4 do        if i>#str64 then            break        end        local data = 0        local str_count=0        for j=0,3 do            local str1=string.sub(str64,i+j,i+j)            if not temp[str1] then                return            end            if temp[str1] < 1 then                data = data * 64            else                data = data * 64 + temp[str1]-1                str_count = str_count + 1            end        end        for j=16,0,-8 do            if str_count > 0 then                str=str..string.char(math.floor(data/math.pow(2,j)))                data=math.mod(data,math.pow(2,j))                str_count = str_count - 1            end        end    end    local last = tonumber(string.byte(str, string.len(str), string.len(str)))    if last == 0 then        str = string.sub(str, 1, string.len(str) - 1)    end    return strend