Re: [PATCH v2] dm: Add support for escaped characters in str_field_delimit()

Benjamin Marzinski
2024-07-02T16:23:50Z

On Tue, Jul 02, 2024 at 05:18:38PM +0200, Mikulas Patocka wrote:
> Hi
>
> I'd like to ask why is this needed. AFAIK, none of the allowed targets use
> ',' on their table line.

',' and ';' are both legal characters in DM names and UUIDs, although I
can't think of a good reason why anyone would want to use them.

-Ben

>
> Mikulas
>
>
> On Thu, 13 Jun 2024, Abhinav Jain wrote:
>
> > Remove all the escape characters that come before separator.
> > Tested this code by writing a dummy program containing the two
> > functions and testing it on below input, sharing results:
> >
> > Original string: "field1\,with\,commas,field2\,with\,more\,commas"
> > Field: "field1"
> > Field: "with"
> > Field: "commas"
> > Field: "field2"
> > Field: "with"
> > Field: "more"
> > Field: "commas"
> >
> > Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
> > ---
> > PATCH v1:
> > https://lore.kernel.org/all/20240609141721.52344-1-jain.abhinav177@gmail.com/
> >
> > Changes since v1:
> > - Modified the str_field_delimit function as per shared feedback
> > - Added remove_escaped_characters function
> > ---
> > ---
> > drivers/md/dm-init.c | 53 +++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 47 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
> > index 2a71bcdba92d..0e31ecf1b48e 100644
> > --- a/drivers/md/dm-init.c
> > +++ b/drivers/md/dm-init.c
> > @@ -76,6 +76,24 @@ static void __init dm_setup_cleanup(struct list_head *devices)
> > }
> > }
> >
> > +/* Remove escape characters from a given field string. */
> > +static void __init remove_escape_characters(char *field)
> > +{
> > + char *src = field;
> > + char *dest = field;
> > +
> > + while (*src) {
> > + if (*src == '\\') {
> > + src++;
> > + if (*src)
> > + *dest++ = *src++;
> > + } else {
> > + *dest++ = *src++;
> > + }
> > + }
> > + *dest = '\0';
> > +}
> > +
> > /**
> > * str_field_delimit - delimit a string based on a separator char.
> > * @str: the pointer to the string to delimit.
> > @@ -87,16 +105,39 @@ static void __init dm_setup_cleanup(struct list_head *devices)
> > */
> > static char __init *str_field_delimit(char **str, char separator)
> > {
> > - char *s;
> > + char *s, *escaped, *field;
> >
> > - /* TODO: add support for escaped characters */
> > *str = skip_spaces(*str);
> > s = strchr(*str, separator);
> > - /* Delimit the field and remove trailing spaces */
> > - if (s)
> > +
> > + /* Check for escaped character */
> > + escaped = strchr(*str, '\\');
> > + while (escaped && (s == NULL || escaped < s)) {
> > + /*
> > + * Move the separator search ahead if escaped
> > + * character comes before.
> > + */
> > + s = strchr(escaped + 1, separator);
> > + escaped = strchr(escaped + 1, '\\');
> > + }
> > +
> > + /* If we found a separator, we need to handle escape characters */
> > + if (s) {
> > + *s = '\0';
> > +
> > + remove_escape_characters(*str);
> > + field = *str;
> > + *str = s + 1;
> > + } else {
> > + /* Handle the last field when no separator is present */
> > + s = *str + strlen(*str);
> > *s = '\0';
> > - *str = strim(*str);
> > - return s ? ++s : NULL;
> > +
> > + remove_escape_characters(*str);
> > + field = *str;
> > + *str = s;
> > + }
> > + return field;
> > }
> >
> > /**
> > --
> > 2.34.1
> >