Re: [RFC PATCH 1/7] fetch-pack: allow NULL negotiator->add_tip
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Aug 5, 2020, 19:53 UTC
- Message-ID
- <xmqqo8noooni.fsf@gitster.c.googlers.com>
- In-Reply-To
- <044a782863dd690ed4e430b3793538f701a850c6.1596590295.git.jonathantanmy@google.com>
Jonathan Tan <jonathantanmy@google.com> writes:
> In a subsequent patch, a null fetch negotiator will be introduced. This > negotiator, among other things, will not need any tip information and > will have a NULL add_tip.
After reading the original code that the patch touches, I know what "a NULL add_tip" is, but it would have been nicer to readers if you said "callback" or "method" or "function".
With or without the "if add_tip method is set to NULL, return without doing anything" optimization, it does make sense to refactor two existing places that do identical things.
If all the current negotiators never have NULL in the .add_tip field, however, I'd suspect that it would make it easier to understand if this step is explained as refactoring duplicated code into a single helper _without_ the early-return for optimization, and then the step that introduces the negotiator that does want to lack add_tip method to add the early return. After all, if the null negotiator added a pointer to a no-op function to its .add_tip field, things would still work correctly without the early-return in the new helper function, no?
Show 9 quoted lines
> Teach fetch-pack to allow this, and to take advantage of this by > avoiding a ref and alternate traversal when it can. To do this, this > patch combines all invocations of functions that invoke add_tip into one > function, and that function first checks whether add_tip is NULL. > > Signed-off-by: Jonathan Tan <jonathantanmy@google.com> > --- > fetch-pack.c | 20 +++++++++++++------- > 1 file changed, 13 insertions(+), 7 deletions(-)
Show 46 quoted lines
>
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 80fb3bd899..6c786f5970 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -240,6 +240,16 @@ static void mark_tips(struct fetch_negotiator *negotiator,
> return;
> }
>
> +static void add_tips_and_alternates(struct fetch_negotiator *negotiator,
> + const struct oid_array *negotiation_tips)
> +{
> + if (!negotiator->add_tip)
> + return;
> +
> + mark_tips(negotiator, negotiation_tips);
> + for_each_cached_alternate(negotiator, insert_one_alternate_object);
> +}
> +
> static int find_common(struct fetch_negotiator *negotiator,
> struct fetch_pack_args *args,
> int fd[2], struct object_id *result_oid,
> @@ -262,10 +272,8 @@ static int find_common(struct fetch_negotiator *negotiator,
> PACKET_READ_CHOMP_NEWLINE |
> PACKET_READ_DIE_ON_ERR_PACKET);
>
> - if (!args->no_dependents) {
> - mark_tips(negotiator, args->negotiation_tips);
> - for_each_cached_alternate(negotiator, insert_one_alternate_object);
> - }
> + if (!args->no_dependents)
> + add_tips_and_alternates(negotiator, args->negotiation_tips);
>
> fetching = 0;
> for ( ; refs ; refs = refs->next) {
> @@ -1575,9 +1583,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
> else
> state = FETCH_SEND_REQUEST;
>
> - mark_tips(negotiator, args->negotiation_tips);
> - for_each_cached_alternate(negotiator,
> - insert_one_alternate_object);
> + add_tips_and_alternates(negotiator, args->negotiation_tips);
> } else {
> filter_refs(args, &ref, sought, nr_sought);
> state = FETCH_SEND_REQUEST;