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Message-ID: <Pine.LNX.4.44L0.0904241534110.4531-100000@iolanthe.rowland.org>
Date: Fri, 24 Apr 2009 16:02:52 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: Kernel development list <linux-kernel@...r.kernel.org>
cc: USB list <linux-usb@...r.kernel.org>
Subject: NLS: utf8 conversions
Although nobody seems to have made a big deal about it, the conversions
between utf8 and utf16 done by fs/nls/nls_base.c are wrong in a couple
of important respects:
They don't handle Unicode code points larger than U+FFFF.
They don't detect invalid values, in particular, surrogate
code points.
The problems stem from the fact the characters at issue can't be
represented by a single 16-bit wchar_t. But that's no excuse for
performing an incorrect conversion to or from utf16.
Are there any definite thoughts on how this should be handled? I don't
see any way for the single-character conversion routines (utf8_mbtowc
and utf8_wctomb) to come to grips with these issues, except perhaps for
returning an error when a character would be invalid or too big to fit
in 16 bits.
The string-oriented routines (utf8_mbstowcs and utf8_wcstombs) could be
adapted to deal with these issues properly.
Any comments or suggestions for other approaches?
Alan Stern
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