Re: [PATCH v3 2/5] config: split do_event() into start and flush operations

[Jonathan Tan <jonathantanmy@google.com>]

Josh Steadmon <steadmon@google.com> writes:
> +static void start_event(struct config_source *cs, enum config_event_t type,
> +		       struct parse_event_data *data)
> +{
> +	data->previous_type = type;
> +	data->previous_offset = get_corrected_offset(cs, type);
> +}

It's a pity that get_corrected_offset() has to be called twice (once
here and once below) but I think that's the best we can do given how the
code is laid out (and I can't think of a better code layout either).

> +static int flush_event(struct config_source *cs, enum config_event_t type,
> +		       struct parse_event_data *data)

One thing confusing here is that the "type" is not what's being flushed,
but used to change details about how we flush. Technically all we need
is is_whitespace_type and is_eof_type, but that's clumsier to code. I
think the best we can do is add some documentation to this function,
maybe 'Flush the event started by a prior start_event(), if one exists.
The type of the event being flushed is not "type" but the type that was
passed to the prior start_event(); "type" here may merely change how the
flush is performed' or something like that.

> +{
> +	if (!data->opts || !data->opts->event_fn)
> +		return 0;
> +
> +	if (type == CONFIG_EVENT_WHITESPACE &&
> +	    data->previous_type == type)
> +		return 0;
>  
>  	if (data->previous_type != CONFIG_EVENT_EOF &&
>  	    data->opts->event_fn(data->previous_type, data->previous_offset,
> -				 offset, cs, data->opts->event_fn_data) < 0)
> +				 get_corrected_offset(cs, type), cs,
> +				 data->opts->event_fn_data) < 0)
>  		return -1;

Another confusing point here is how EOF is used both to mean
"start_event() was never called" and a true EOF. I think for now it's
best to just document this where we define CONFIG_EVENT_EOF.