linux-kernel - Re: [PATCH] dm: Add support for escaped characters in str_field

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Message-ID: <Zmc3vrfFglYISw1P@redhat.com>
Date: Mon, 10 Jun 2024 13:28:30 -0400
From: Benjamin Marzinski <bmarzins@...hat.com>
To: Abhinav Jain <jain.abhinav177@...il.com>
Cc: agk@...hat.com, snitzer@...nel.org, mpatocka@...hat.com,
        dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org, javier.carrasco.cruz@...il.com
Subject: Re: [PATCH] dm: Add support for escaped characters in
 str_field_delimit()

On Mon, Jun 10, 2024 at 01:11:40PM -0400, Benjamin Marzinski wrote:
> On Sun, Jun 09, 2024 at 02:17:21PM +0000, Abhinav Jain wrote:
> > Add a new variable for escaped characters.
> > 
> > If an escaped character (\) is found before the separator, and if the 
> > separator is not found or if the escaped character is located before the
> > separator, then move the separator ahead and continue searching for the
> > next separator.
> > 
> > Return the pointer to remainder string after the delimiter. If the
> > separator was found, return a pointer to the character immediately after
> > the delimiter (s + 1). If the separator was not found, return NULL.
> 
> This doesn't do anything to the escape character. Presumably you want to
> pass the field containing a separator down to dm_eary_create(). But you
> don't want to pass the escape character itself.
> 
> To work correctly, this code needs to remove all those escape characters
> that come before separators. It probably needs to do something like:
> 
> 1. Find a next non-escaped separator and change it to NULL, so you have
> your field string.

And by NULL, I mean '\0'.

-Ben

> 
> 2. Find all the escaped separators in the field string, and shift the
> rest of the string over to overwrite the escape character with the rest
> of the string.
> 
> -Ben
> 
> > 
> > Signed-off-by: Abhinav Jain <jain.abhinav177@...il.com>
> > ---
> >  drivers/md/dm-init.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
> > index 2a71bcdba92d..bef6a582a4ae 100644
> > --- a/drivers/md/dm-init.c
> > +++ b/drivers/md/dm-init.c
> > @@ -87,11 +87,21 @@ 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;
> >  
> > -	/* TODO: add support for escaped characters */
> >  	*str = skip_spaces(*str);
> >  	s = strchr(*str, separator);
> > +
> > +	/* Check for escaped character */
> > +	escaped = strchr(*str, '\\');
> > +	if (escaped && (s == NULL || escaped < s)) {
> > +		/*
> > +		 * If escaped character comes before the separator, move
> > +		 * the separator ahead & continue searching for next one.
> > +		 */
> > +		s = strchr(escaped + 1, separator);
> > +	}
> > +
> >  	/* Delimit the field and remove trailing spaces */
> >  	if (s)
> >  		*s = '\0';
> > -- 
> > 2.34.1
> >