Re: [PATCH v2 2/4] Add structure representing hash algorithm

> Since in the future we want to support an additional hash algorithm, add
> a structure that represents a hash algorithm and all the data that must
> go along with it.  Add a constant to allow easy enumeration of hash
> algorithms.  Implement function typedefs to create an abstract API that
> can be used by any hash algorithm, and wrappers for the existing SHA1
> functions that conform to this API.
> [...]
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
> diff --git a/cache.h b/cache.h
> @@ -77,6 +77,61 @@ struct object_id {
> +typedef void (*git_hash_init_fn)(void *ctx);
> +typedef void (*git_hash_update_fn)(void *ctx, const void *in, size_t len);
> +typedef void (*git_hash_final_fn)(unsigned char *hash, void *ctx);
> +
> +struct git_hash_algo {
> +       [...]
> +       /* The hash initialization function. */
> +       git_hash_init_fn init_fn;
> +
> +       /* The hash update function. */
> +       git_hash_update_fn update_fn;
> +
> +       /* The hash finalization function. */
> +       git_hash_final_fn final_fn;
> +       [...]
> +};
> diff --git a/sha1_file.c b/sha1_file.c
> @@ -39,6 +39,49 @@ const struct object_id empty_blob_oid = {
> +static inline void git_hash_sha1_init(void *ctx)
> +{
> +       git_SHA1_Init((git_SHA_CTX *)ctx);
> +}
> +
> +static inline void git_hash_sha1_update(void *ctx, const void *data, size_t len)
> +{
> +       git_SHA1_Update((git_SHA_CTX *)ctx, data, len);
> +}
> +
> +static inline void git_hash_sha1_final(unsigned char *hash, void *ctx)
> +{
> +       git_SHA1_Final(hash, (git_SHA_CTX *)ctx);
> +}

> +const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
> +       [...]
> +       {
> +               "sha-1",
> +               /* "sha1", big-endian */
> +               0x73686131,
> +               sizeof(git_SHA_CTX),
> +               GIT_SHA1_RAWSZ,
> +               GIT_SHA1_HEXSZ,
> +               git_hash_sha1_init,
> +               git_hash_sha1_update,
> +               git_hash_sha1_final,
> +               &empty_tree_oid,
> +               &empty_blob_oid,
> +       },
> +};