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    SubjectRe: [PATCH] Smackv10: Smack rules grammar + their stateful parser
    On 11/6/07, Adrian Bunk <bunk@kernel.org> wrote:
    > On Tue, Nov 06, 2007 at 01:34:05PM +0200, Ahmed S. Darwish wrote:
    > > Hi,
    > >
    > > On Tue, Nov 06, 2007 at 09:56:51AM +0100, Adrian Bunk wrote:
    > > > On Tue, Nov 06, 2007 at 03:26:12AM -0500, Kyle Moffett wrote:
    > > > > On Nov 06, 2007, at 01:33:05, Adrian Bunk wrote:
    > > > >> Can you limit this to 7bit ASCII and use isascii() somewhere?
    > > > >>
    > > > >> Otherwise I'd expect funny things to happen when you e.g. use isspace() on
    > > > >> the UTF-8 encoded character ??.
    > > > >
    > > > > Actually, you don't need to. You tell them it expects UTF-8 encoded
    > > > > strings and be done with it. All US-ASCII characters from 0 through 127
    > > > > (IE: high bit clear) are exactly the same in UTF-8, and UTF-8 special
    > > > > characters have the high bit set in all bytes. Therefore you just assume
    > > > > that anything with the high bit set is part of a word and you can handle
    > > > > basic UTF-8. (It doesn't work on special UTF-8 space characters like
    > > > > nonbreaking space and similar, but handling those is significantly more
    > > > > complicated).
    > > >
    > > > The documentations says:
    > > > "Smack labels cannot contain unprintable characters or the "/" (slash)
    > > > character."
    > > >
    > > > What you propose might contain unprintable characters, and it might even
    > > > be invalid UTF-8.
    > >
    > > As far as I understand the problem now, isspace() accepts the 0xa0
    > > character which might collide with some of UTF-8 encoded characters
    > > cause the high bit is set.
    > >
    > > I used "if (!isspace(c) && !isgraph(c)) return -EINVAL;" to test
    > > rules' characters validity which seems not enough. I'll add !isascii(c)
    > > in the condition and ask Casey to change the documentation to be
    > > something like:
    > >
    > > Smack labels are represented in ASCII characters, they cannot contain
    > > unprintable characters or the '/' (slash) character.
    > >
    > > and in write():
    > > if (!isascii(c) return -EINVAL;
    > > if (!isspace(c) && !isgraph(c)) return -EINVAL;
    > >
    > > This satisfy above customized labels rule, right ?
    >
    > It should work for all charsets you'll usually have to handle.
    >

    I admit I'm not experienced in such encoding stuff, but shouldn't the
    ASCII and the ASCII-compatible UTF-8 encodings be enough for the
    labels ?

    > It would not work if someone would e.g. give you UTF-16 encoded strings,
    > but I don't see this happening in practice.

    Won't this complicate the code too much ?

    --
    Ahmed S. Darwish
    Homepage: http://darwish.07.googlepages.com
    Blog: http://darwish-07.blogspot.com
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