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Re: [Libvir] [PATCH] Enhance virBuffer code



On Fri, Dec 14, 2007 at 08:34:13AM +0100, Jim Meyering wrote:
> Daniel Veillard <veillard redhat com> wrote:
> 
> > On Thu, Dec 13, 2007 at 11:21:31PM +0100, Jim Meyering wrote:
> >> "Richard W.M. Jones" <rjones redhat com> wrote:
> >> ...
> >> > + * virBufferURIEncodeString:
> >> > + * @buf:  the buffer to append to
> >> > + * @str:  the string argument which will be URI-encoded
> >> > + *
> >> > + * Append the string to the buffer.  The string will be URI-encoded
> >> > + * during the append (ie any non alpha-numeric characters are replaced
> >> > + * with '%xx' hex sequences).
> >> > + *
> >> > + * Returns 0 successful, -1 in case of internal or API error.
> >> > + */
> >> > +int
> >> > +virBufferURIEncodeString (virBufferPtr buf, const char *str)
> >> > +{
> >> > +    int grow_size = 0;
> >> > +    const char *p;
> >> > +    unsigned char uc;
> >> > +    const char *hex = "0123456789abcdef";
> >> > +
> >> > +    for (p = str; *p; ++p) {
> >> > +        /* Want to leave only strict 7 bit ASCII alphanumerics ... */
> >> > +        if ((*p >= '0' && *p <= '9') ||
> >> > +            (*p >= 'a' && *p <= 'z') ||
> >> > +            (*p >= 'A' && *p <= 'Z'))
> >> ...
> >> > +    for (p = str; *p; ++p) {
> >> > +        if ((*p >= '0' && *p <= '9') ||
> >> > +            (*p >= 'a' && *p <= 'z') ||
> >> > +            (*p >= 'A' && *p <= 'Z'))
> >>
> >> Hi Rich,
> >>
> >> What do you think of using this?
> >>
> >>   isascii (*p) && isalnum (*p)
> >
> >   I have learned to be very cautious of the is* macros because they
> > tend to be local dependant whichis usually really not what you would
> > like or expect. In that case this may work, but explicit ranges
> > are 100% clear about what you intend to accept or not, that's why I
> > usually prefer them.
> 
> You're right that we shouldn't use isalnum here.
> However, we shouldn't use inequality comparisons, either.
> While 0 <= c <= 9 is guaranteed to be ok for the digits, the
> a..z and A..Z ranges need not be contiguous, i.e., with EBCDIC:

Seriously who gives a damn about EBCDIC anymore. This just makes it totally
unreadable.

Dan.
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