On Tue, May 09, 2023 at 01:18:13PM -0500, Eric Blake wrote:
> On Tue, May 09, 2023 at 03:51:18PM +0100, Richard W.M. Jones wrote:
> > eg. { '\r', '\n' } -> { '\\', 'n', '\\', 'r' }
> > ---
> > common/utils/utils.h | 1 +
> > common/utils/quote.c | 58 ++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 59 insertions(+)
> >
>
> > +
> > +/* Print str to fp, quoting in a way similar to C strings, for example
> > + * '\n' -> "\n".
> > + *
> > + * Note that we do not emit quotes around the string, and double
> > + * quotes within the string are not escaped.
> > + */
> > +void
> > +c_string_quote (const char *str, FILE *fp)
> > +{
> > + size_t i;
> > + char c;
> > +
> > + for (i = 0; c = str[i], c != '\0'; ++i) {
> > + if (ascii_isprint (c))
> > + fputc (c, fp);
>
> ascii_isprint('\\') returns true, which means you output just one
> backslash; but that's one where you really want to output two.
> Otherwise, you can't tell the difference on the output from the
> C-string input of one-byte "\a" vs. two-byte "\\a". :(
>
> > + else {
> > + switch (c) {
> ...
> > + default:
> > + fputc ('\\', fp);
> > + fputc ('x', fp);
> > + fputc (hexchar (c >> 4), fp);
> > + fputc (hexchar (c), fp);
> > + }
>
> You mentioned in the commit message that not escaping " is
> intentional; and I can live with that for this patch. But if we need
> to add it in the future, it will be easier to rejigger the loop as
> (abbreviated, but you get the idea):
>
> for (i = 0; c = str[i], c != '\0'; ++i) {
> switch (c) {
> case '\\': fputc ('\\'); fputc ('\\'); break;
> case '\a': fputc ('\\'); fputc ('a'); break;
> ...
> default:
> if (isprint (c)
> fputc (c);
> else {
> // output \xXX
> }
> }
> }
Yes this is a good idea anyway, I will make a change like this.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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