On Tue, Aug 26, 2014 at 2:38 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Ronnie Sahlberg <sahlberg@xxxxxxxxxx> writes:
>
>> diff --git a/refs-be-files.c b/refs-be-files.c
>> index e58a7e1..27eafd0 100644
>> --- a/refs-be-files.c
>> +++ b/refs-be-files.c
>> ...
>> +struct ref_be refs_files = {
>> + files_transaction_begin,
>> + files_transaction_update_sha1,
>> + files_transaction_create_sha1,
>> + files_transaction_delete_sha1,
>> + files_transaction_update_reflog,
>> + files_transaction_commit,
>> + files_transaction_free,
>> +};
>> +
>> +struct ref_be *refs = &refs_files;
>
>> diff --git a/refs.c b/refs.c
>> index 6b434ad..b8c942f 100644
>> --- a/refs.c
>> +++ b/refs.c
>> ...
>> +void transaction_free(struct ref_transaction *transaction)
>> +{
>> + return refs->transaction_free(transaction);
>> +}
>> diff --git a/refs.h b/refs.h
>> index a14fc5d..4b669f5 100644
>> --- a/refs.h
>> +++ b/refs.h
>> ...
>> +struct ref_be {
>> + transaction_begin_fn transaction_begin;
>> + transaction_update_sha1_fn transaction_update_sha1;
>> + transaction_create_sha1_fn transaction_create_sha1;
>> + transaction_delete_sha1_fn transaction_delete_sha1;
>> + transaction_update_reflog_fn transaction_update_reflog;
>> + transaction_commit_fn transaction_commit;
>> + transaction_free_fn transaction_free;
>> +};
>> +
>> +extern struct ref_be *refs;
>> +
>> #endif /* REFS_H */
>
> The overall structure is certainly nice, but this means you only can
> LINK with one backend. Is that what we really want?
>
> I would have expected something like this:
>
> * In refs.c, there is a "static struct ref_be *the_refs_backend"
> that points at the chosen singleton backend;
Done.
It is also initialized to default to the files backend :
refs.c:
/* We always have a files backend and it is the default */
struct ref_be *the_refs_backend = &refs_be_files;
This does make "refs_be_files" and later "refs_be_db" public symbols instead of
the singleton. But we probably want/need these structures to be public anyway
if we at some stage want to be able to switch between backends at runtime.
refs.h:
extern struct ref_be refs_be_files;
void set_refs_backend(struct ref_be *ref_be);
Thus allowing us to
set_refs_backend(&refs_be_files) to switch back to the files backend.
>
> * Upon start-up, set_refs_backend() function that is exported from
> refs.c can be used to set the_refs_backend;
>
> * Each refs-be-frotz.c will export "struct ref_be refs_frotz" (or
> perhaps "struct refs_be refs_be_frotz") to the outside world, so
> that the start-up code can call set_refs_backend() with it.
Yepp.
refs-be-db.c: does this.
>
> * It is probably sensible to keep the_refs_backend default to
> &refs_be_files.
>
Yepp.
https://github.com/rsahlberg/git/tree/backend-struct-db
https://github.com/rsahlberg/git/tree/backend-struct-db-2 (adds a db
backend and daemon)
Thanks. Good suggestions.
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