hash: add a function to look up hash algo structs

In C, it's easy for us to look up a hash algorithm structure by its
offset by simply indexing the hash_algos array.  However, in Rust, we
sometimes need a pointer to pass to a C function, but we have our own
hash algorithm abstraction.

To get one from the other, let's provide a simple function that looks up
the C structure from the offset and expose it in Rust.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/hash.h b/hash.h
index 99c9c2a0a8..709d7585a5 100644
--- a/hash.h
+++ b/hash.h
@@ -340,6 +340,7 @@ static inline void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx
 	ctx->algop->final_oid_fn(oid, ctx);
 }
 
+const struct git_hash_algo *hash_algo_ptr_by_number(uint32_t algo);
 /*
  * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
  * the name doesn't match a known algorithm.