需要将UTF8和UTF16 .csv文件转换为ASCII

I have Script to convert the .csv files which are in UTF8 format to ASCII format. now i wanted to convert the files which are in UTF16 also and if the file is in ASCII keep as is. i am using below code to change the UTF8 and UTF16 separately. help on this to do in a single script. I have Script to convert the .csv files which a