Re: [PATCH 2/2] xfs_db: add helper for flist_find_type for clearer field matching

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Apr 16, 2024 at 10:28:42PM +0200, Andrey Albershteyn wrote:
> Make flist_find_type() more readable by unloading field type
> matching to the helper.
> 
> Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
> ---
>  db/flist.c | 59 ++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 37 insertions(+), 22 deletions(-)
> 
> diff --git a/db/flist.c b/db/flist.c
> index 0a6cc5fcee43..18052a744a65 100644
> --- a/db/flist.c
> +++ b/db/flist.c
> @@ -400,6 +400,40 @@ flist_split(
>  	return v;
>  }
>  
> +flist_t *
> +flist_field_match(

Is this function going to be used outside of this module, or should it
be declared static?

> +	const field_t		*field,
> +	fldt_t			type,
> +	void			*obj,
> +	int			startoff)
> +{
> +	flist_t			*fl;
> +	int			count;
> +	const ftattr_t		*fa;
> +
> +	fl = flist_make(field->name);
> +	fl->fld = field;
> +	if (field->ftyp == type)
> +		return fl;
> +	count = fcount(field, obj, startoff);
> +	if (!count)
> +		goto out;
> +	fa = &ftattrtab[field->ftyp];
> +	if (fa->subfld) {

You could do:

	if (!fa->subfld)
		goto out;

	nfl = flist_find_ftyp(...);

to reduce the indenting here.  But I think you were trying to make
before and after as identical as possible, right?

> +		flist_t *nfl;
> +
> +		nfl = flist_find_ftyp(fa->subfld, type, obj, startoff);
> +		if (nfl) {
> +			fl->child = nfl;
> +			return fl;
> +		}
> +	}
> +
> +out:
> +	flist_free(fl);
> +	return NULL;
> +}
> +
>  /*
>   * Given a set of fields, scan for a field of the given type.
>   * Return an flist leading to the first found field
> @@ -413,33 +447,14 @@ flist_find_ftyp(
>  	void		*obj,
>  	int		startoff)
>  {
> -	flist_t	*fl;
>  	const field_t	*f;
> -	int		count;
> -	const ftattr_t  *fa;
> +	flist_t		*fl;
>  
>  	for (f = fields; f->name; f++) {
> -		fl = flist_make(f->name);
> -		fl->fld = f;
> -		if (f->ftyp == type)
> +		if ((fl = flist_field_match(f, type, obj, startoff)) != NULL)
>  			return fl;

Normally these days we expand assign-and-check when not in a loop
control test:

		fl = flist_field_match(...);
		if (fl)
			return fl;

But those last two comments merely reflect my style preference; the
question I care most about is the one about the static attribute.

--D

> -		count = fcount(f, obj, startoff);
> -		if (!count) {
> -			flist_free(fl);
> -			continue;
> -		}
> -		fa = &ftattrtab[f->ftyp];
> -		if (fa->subfld) {
> -			flist_t *nfl;
> -
> -			nfl = flist_find_ftyp(fa->subfld, type, obj, startoff);
> -			if (nfl) {
> -				fl->child = nfl;
> -				return fl;
> -			}
> -		}
> -		flist_free(fl);
>  	}
> +
>  	return NULL;
>  }
>  
> -- 
> 2.42.0
> 
>