[Libvir] [PATCH] Enhance virBuffer code
Richard W.M. Jones
rjones at redhat.com
Fri Dec 14 10:33:03 UTC 2007
Jim Meyering wrote:
> "Richard W.M. Jones" <rjones at redhat.com> wrote:
>> Jim Meyering wrote:
>>> What do you think of using this?
>>>
>>> isascii (*p) && isalnum (*p)
>> I'm not sure I'm qualified to say what this does on EBCDIC, but quite
>> likely lots of other code breaks there too anyway. This is nicely
>> self-documenting anyway.
>
> As Daniel suggested, isalnum is locale-sensitive.
> If there's a locale with an alphabetic byte that is outside
> the logical a-zA-Z range, yet still within 0..127, then the above
> expression will give a false-positive for that byte.
>
> I've been inclined to stop worrying about EBCDIC for years, but a quick
> search on the web finds that people are still stuck using it, and do
> report bugs in ASCII-assuming code.
>
> This is why autoconf goes to the trouble of doing this:
> tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
> not this:
> tr a-z A-Z
> to convert to upper case.
Another factor to consider here is that it doesn't matter if this
function over-escapes, but it does matter if the function under-escapes.
That is to say, it could escape every character as a %xx hex code,
which would be ugly and slightly inefficient but not wrong.
Rich.
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