Re: [PATCH] list-objects-filter: merge filter data structs

[Junio C Hamano <gitster@pobox.com>]

Matthew DeVore <matvore@comcast.net> writes:

> Simplify the filter execution data logic and structs by putting all
> execution data for all filter types in a single struct. This results in
> a tiny overhead for each filter instance, and in exchange, invoking
> filters is not only easier but the list-objects-filter public API is
> simpler and more opaque.

Hmmm...

> +struct filter_data {
> +	/* Used by all filter types. */
>  	struct oidset *omits;
> +
> +	enum list_objects_filter_result (*filter_object_fn)(
> +		struct repository *r,
> +		enum list_objects_filter_situation filter_situation,
> +		struct object *obj,
> +		const char *pathname,
> +		const char *filename,
> +		struct filter_data *filter_data);
> +
> +	/* BEGIN tree:<depth> filter data */
> +
> +	/*
> +	 * Maps trees to the minimum depth at which they were seen. It is not
> +	 * necessary to re-traverse a tree at deeper or equal depths than it has
> +	 * already been traversed.
> +	 *
> +	 * We can't use LOFR_MARK_SEEN for tree objects since this will prevent
> +	 * it from being traversed at shallower depths.
> +	 */
> +	struct oidmap seen_at_depth;
> +
> +	unsigned long exclude_depth;
> +	unsigned long current_depth;
> +
> +	/* BEGIN blobs:limit=<limit> filter data */
> +
> +	unsigned long max_bytes;
> +
> +	/* BEGIN sparse:... filter data */
> +
> +	struct exclude_list el;
> +
> +	size_t nr, alloc;
> +	struct frame *array_frame;
>  };

I am hoping that I am not misreading the intention but you do not
plan to use the above so that you can say "apply 'tree:depth=4' and
'blobs:limit=1G' at the same time" by filling the fields in a single
struct, do you?  For combined filter, you'll still have multiple
instances of filter_data struct, strung together in a list that says
"all of these must be satisfied" or something like that, right?

And if that is the case, I am not sure why the above "struct with
all these fields" is a good idea.  If these three (and probably we
will have more as the system evolves) sets of fields in this outer
struct for different filters were enclosed in a union, that would be
a different story, though.