There is no "exception" in encoding. The non-breaking space 0xA0 is not
ASCII, and therefore returning "ASCII" will later create issues (for
instance trying to re-encode with iconv produces an error).
This was obviously an explicit decision in original code (according to
code comments), probably tied to specifity of the original program from
Mozilla. Now we want strict detection.
I will return "ISO-8859-1" for "nearly-ASCII texts with NBSP as only
exception" (note that I could have returned any ISO-8859 charsets since
they all have this character in common).
According to RFC 2781, section 3.3: "Systems labelling UTF-16BE/LE text
MUST NOT prepend a BOM to the text."
Since uchardet cannot (and should not, obviously, it's not its role)
modify input text, when a BOM is present, we should always label the
encoding as "UTF-16" only.
Also it broke unit tests in using programs since a conversion from UTF-8
to UTF-16LE/BE would create a text without BOM, and a conversion from
UTF-16LE/BE to UTF-8 creates a UTF-8 text with a BOM, which changed
existing behaviours.
Same goes for UTF-32.
See also Unicode 5.0.0 standard, section 3.10 (tables 3.8 and 3.9 in
particular).
The lib used to return "" for both properly detected ASCII and
detection failure. And the tool would return "ascii/unknown".
Make a proper distinction between the 2 cases.
