How to know whether a file's encoding is ansi or utf8?

[Alexandre via Digitalmars-d-learn]

http://www.architectshack.com/TextFileEncodingDetector.ashx

On Tuesday, 22 July 2014 at 15:53:23 UTC, FreeSlave wrote:
> Note that BOMs are optional and may be not presented in Unicode 
> file. Also presence of leading bytes which look BOM does not 
> necessarily mean that file is encoded in some kind of Unicode.


There are several difficulties in this case ...