Html::encoding helps to determine the encoding of html and xml/xhtml documents. it can export the following functions:

encoding_from_content - extracts charset from the content-type header value.
encoding_from_byte_order_mark - read byte order mark from an octet sequence.
encoding_from_xml_declaration - extract encoding xml or text declaration.
encoding_from_first_chars - can be useful to distinguish utf-16le from utf-8.
encoding_from_meta_element - looks at .
encoding_from_xml_document - a best guess from a list of suspected encodings.
encoding_from_html_document - a best guess from a list of suspected encodings.
encoding_from_http_message - takes an http::message and returns the encoding.