Now the UTF-8 prober would not only detect valid UTF-8, but would also
detect the most probable language. Using the data generated 2 commits
away, this works very well.
This is still basic and will require even more improvements. In
particular, now the nsUTF8Prober should return an array of ("UTF-8",
language) couple candidate. And nsMBCSGroupProber should itself forward
these candidates as well as other candidates from other multi-byte
detectors. This way, the public-facing API would get more probable
candidates, in case the algorithm is slightly wrong.
Also the UTF-8 confidence is currently stupidly high as soon as we
consider it to be right. We should likely weigh it with language
detection (in particular, if no language is detected, this should
severely weigh down UTF-8 detection; not to 0, but high enough to be a
fallback in case no other encoding+lang is valid and low enough to give
chances to other good candidate couples.
This doesn't work for all probers yet, in particular not for the most
generic probers (such as UTF-8) or WINDOWS-1252. These will return NULL.
It's still a good first step.
Right now, it returns the 2-character language code from ISO 639-1. A
using project could easily get the English language name from the
XML/json files provided by the iso-codes project. This project will also
allow to easily localize the language name in other languages through
gettext (this is what we do in GIMP for instance). I don't add any
dependency though and leave it to downstream projects to implement this.
I was also wondering if we want to support region information for cases
when it would make sense. I especially wondered about it for Chinese
encodings as some of them seem quite specific to a region (according to
Wikipedia at least). For the time being though, these just return "zh".
We'll see later if it makes sense to be more accurate (maybe depending
on reports?).
Preparing for an updated API which will also allow to loop at the
confidence value, as well as get the list of possible candidate (i.e.
all detected encoding which had a confidence value high enough so that
we would even consider them).
It is still only internal logics though.
ASCII and ISO-8859-1 should not be detected in
nsUniversalDetector::HandleData() but in nsUniversalDetector::DataEnd()
instead. Otherwise it creates an unwanted shortcut from the first call
to uchardet_handle_data() if the input is broken into several pieces and
if the first chunk happens to be ASCII (or ASCII + NBSP).
Not sure if this is useful to have the 'if (mDetectedCharset)' outside
the if block, but it won't hurt for sure in this specific case, so I
leave the current code logics as is.
The exact warning was:
nsUniversalDetector.cpp: In member function ‘virtual nsresult nsUniversalDetector::HandleData(const char*, PRUint32)’:
nsUniversalDetector.cpp:115:5: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
if (aLen > 2)
^~
nsUniversalDetector.cpp:157:7: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘if’
if (mDetectedCharset)
^~
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.
