Subject: Re: [PATCH iproute2-next 3/9] dcb: app: modify dcb-app print functions for dcb-rewr reuse

From: Petr Machata <[email-masked]>
Date: Tue, 23 May 2023 15:23:46 +0200

Daniel Machon <[email-masked]> writes:

> -static void dcb_app_print_filtered(const struct dcb_app_table *tab,
> -				   bool (*filter)(const struct dcb_app *),
> -				   int (*print_key)(__u16 protocol),
> -				   const char *json_name,
> -				   const char *fp_name)
> +void dcb_app_print_filtered(const struct dcb_app_table *tab,
> +			    bool (*filter)(const struct dcb_app *),
> +			    int (*print_pid)(__u16 protocol),
> +			    const char *json_name, const char *fp_name)
>  {
>  	bool first = true;
>  	size_t i;
> @@ -439,8 +437,14 @@ static void dcb_app_print_filtered(const struct dcb_app_table *tab,
>  		}
>  
>  		open_json_array(PRINT_JSON, NULL);
> -		print_key(app->protocol);
> -		print_uint(PRINT_ANY, NULL, "%d ", app->priority);
> +		if (tab->attr == DCB_ATTR_IEEE_APP_TABLE) {
> +			print_pid(app->protocol);
> +			print_uint(PRINT_ANY, NULL, ":%d", app->priority);
> +		} else {
> +			print_uint(PRINT_ANY, NULL, "%d:", app->priority);
> +			print_pid(app->protocol);
> +		}

I really dislike the attribute dispatch. I feels too much like mixing
abstraction layers. I think the callback should take a full struct
dcb_app pointer and format it as appropriate. Then you can model the
rewrite table differently from the app table by providing a callback
that invokes the print_ helpers in the correct order.

The app->protocol field as such is not really necessary IMHO, because
the function that invokes the helpers understands what kind of table it
is dealing with and could provide it as a parameter. But OK, I guess it
makes sense and probably saves some boilerplate parameterization.

> +		print_string(PRINT_ANY, NULL, "%s", " ");
>  		close_json_array(PRINT_JSON, NULL);
>  	}
>