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https://issues.apache.org/jira/browse/TIKA-721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13119035#comment-13119035
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Michael McCandless commented on TIKA-721:
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bq. I'd suggest we check for invalid UTF-16 sequences (see
http://unicode.org/faq/utf_bom.html#utf16-7 for which ranges aren't allowed).
I tried to do that: if I see unpaired surrogate, or invalid pair, then
I count that as invalid.
If I decode to a Unicode code point, I then call Java's
Character.isDefined to see if it's really valid, though I'm not sure
this catches all the invalid cases from that FAQ.
bq. If we don't find any invalid ones, then we'll still need to do some
detection. Looking for 0-255+0,0-255+0 or 0+0-255,0+0-255 will work well for
western european stuff, but others will probably need fancy munging of existing
ngrams....
I didn't try to any language detection (I leave language null), except
for the "many chars fall into single block" simple heuristic.
> UTF16-LE not detected
> ---------------------
>
> Key: TIKA-721
> URL: https://issues.apache.org/jira/browse/TIKA-721
> Project: Tika
> Issue Type: Bug
> Components: parser
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Priority: Minor
> Attachments: Chinese_Simplified_utf16.txt, TIKA-721.patch
>
>
> I have a test file encoded in UTF16-LE, but Tika fails to detect it.
> Note that it is missing the BOM, which is not allowed (for UTF16-BE
> the BOM is optional).
> Not sure we can realistically fix this; I have no idea how...
> Here's what Tika detects:
> {noformat}
> windows-1250: confidence=9
> windows-1250: confidence=7
> windows-1252: confidence=7
> windows-1252: confidence=6
> windows-1252: confidence=5
> IBM420_ltr: confidence=4
> windows-1252: confidence=3
> windows-1254: confidence=2
> windows-1250: confidence=2
> windows-1252: confidence=2
> IBM420_rtl: confidence=1
> windows-1253: confidence=1
> windows-1250: confidence=1
> windows-1252: confidence=1
> windows-1252: confidence=1
> windows-1252: confidence=1
> windows-1252: confidence=1
> windows-1252: confidence=1
> {noformat}
> The test file decodes fine as UTF16-LE; eg in Python just run this:
> {noformat}
> import codecs
> codecs.getdecoder('utf_16_le')(open('Chinese_Simplified_utf16.txt').read())
> {noformat}
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