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Re: T.61 -> Unicode conversion
Hallvard B Furuseth wrote:
Also,
I'm pretty sure that when I used X.500 and T.61 (10+ years ago?), at
least the T.61 Underline combining character could be combined with
other combining characters. I don't know if Unicode allows that; the
strprep description of doing so at the end of Appendix A does not.
You're right, the notes I read state that the Underline can be combined
with any other graphic character. I'll have to double-check how Unicode
deals with this.
Also, I may remember wrong but there seems to be a lot more valid
character combinations (accent character + other character) than there
was in the T.61 I am used to. Does the strprep algorithm accept any
T.61 character combination which can be mapped to Unicode, whether or
not the combination is valid in T.61? If so, there are strings which
Stringprep will incorrectly will treat as valid.
Appendix A doesn't specify that invalid combinations should be detected.
Perhaps it should, but it seems unfriendly to break any software that
might be using these sequences.
I don't know where to find T.61 so I can check this, though. At least
not on a Sunday:-)
Considering that the CCITT withdrew this spec years ago, it's not
surprising. It also has never been clear which version T.61 to use, as
that spec evolved quite a bit before being withdrawn. (e.g.,
http://www.mail-archive.com/openca-users@lists.sourceforge.net/msg04365.html
Appendix A only considers iso-ir-103 as listed in RFC1345 but there's
really no way to know how many implementations out there did things
differently.
--
-- Howard Chu
Chief Architect, Symas Corp. Director, Highland Sun
http://www.symas.com http://highlandsun.com/hyc
Symas: Premier OpenSource Development and Support