source_sink->encoding

source_sink ->encoding: {octet,ascii,iso_latin_1,text,utf8,unicode_be,unicode_le,wchar}

Encoding of the data-source:

binary: The source contains binary data (i.e. an octed stream).
iso_latin_1: The source contains text in ISO Latin-1 format.
utf8: The source contains UCS/UNICODE characters encoded using the multibyte UTF-8 encoding.
unicode_le , unicode_be: The source contains 16-but UNICODE-2 characters in little- or big endian encoding
wchar: The source contains a sequence of wchar_t objects. This internally format is implementation defined, both in terms of the number of bytes per character as the byte-order.
See also file->initialise.