Subject: Re: [PATCH v2 3/7] reftable/system: stop depending on "hash.h"

From: Junio C Hamano <[email-masked]>
Date: Tue, 12 Nov 2024 14:53:46 +0900

Patrick Steinhardt <[email-masked]> writes:

> diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c
> index 3c6107c7ce5..7d86d920970 100644
> --- a/refs/reftable-backend.c
> +++ b/refs/reftable-backend.c
> @@ -15,6 +15,7 @@
>  #include "../object.h"
>  #include "../path.h"
>  #include "../refs.h"
> +#include "../reftable/reftable-basics.h"
>  #include "../reftable/reftable-stack.h"
>  #include "../reftable/reftable-record.h"
>  #include "../reftable/reftable-error.h"
> @@ -289,7 +290,16 @@ static struct ref_store *reftable_be_init(struct repository *repo,
>  	refs->store_flags = store_flags;
>  	refs->log_all_ref_updates = repo_settings_get_log_all_ref_updates(repo);
>  
> -	refs->write_options.hash_id = repo->hash_algo->format_id;
> +	switch (repo->hash_algo->format_id) {
> +	case GIT_SHA1_FORMAT_ID:
> +		refs->write_options.hash_id = REFTABLE_HASH_SHA1;
> +		break;
> +	case GIT_SHA256_FORMAT_ID:
> +		refs->write_options.hash_id = REFTABLE_HASH_SHA256;
> +		break;
> +	default:
> +		BUG("unknown hash algorithm %d", repo->hash_algo->format_id);
> +	}
>  	refs->write_options.default_permissions = calc_shared_perm(0666 & ~mask);
>  	refs->write_options.disable_auto_compact =
>  		!git_env_bool("GIT_TEST_REFTABLE_AUTOCOMPACTION", 1);

OK.  With this step, together with the previous one, we let Git side
to use GIT_SHA{1,256}_FORMAT_ID to specify what algorithm is in use
in the repository, and reftable-backend.c layer is responsible for
translating them into REFTABLE_HASH_SHA{1,256}, which is internally
used in reftable library to convey the same thing.

Which makes sense.

> diff --git a/reftable/reftable-basics.h b/reftable/reftable-basics.h
> index 6e8e636b716..e0397ed5836 100644
> --- a/reftable/reftable-basics.h
> +++ b/reftable/reftable-basics.h
> @@ -11,6 +11,19 @@
>  
>  #include <stddef.h>
>  
> +/*
> + * Hash functions understood by the reftable library. Note that the values are
> + * arbitrary and somewhat random such that we can easily detect cases where the
> + * hash hasn't been properly set up.
> + */
> +enum reftable_hash {
> +	REFTABLE_HASH_SHA1   = 89,
> +	REFTABLE_HASH_SHA256 = 247,
> +};

;-).

> +#define REFTABLE_HASH_SIZE_SHA1   20
> +#define REFTABLE_HASH_SIZE_SHA256 32
> +#define REFTABLE_HASH_SIZE_MAX    REFTABLE_HASH_SIZE_SHA256
> +
>  /* Overrides the functions to use for memory management. */
>  void reftable_set_alloc(void *(*malloc)(size_t),
>  			void *(*realloc)(void *, size_t), void (*free)(void *));

OK.