hash: expose hash context functions to Rust

We'd like to be able to hash our data in Rust using the same contexts as
in C.  However, we need our helper functions to not be inline so they
can be linked into the binary appropriately.  In addition, to avoid
managing memory manually and since we don't know the size of the hash
context structure, we want to have simple alloc and free functions we
can use to make sure a context can be easily dynamically created.

Expose the helper functions and create alloc, free, and init functions
we can call.

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

Author: bk2204

hash.c

@@ -246,6 +246,41 @@ const struct git_hash_algo *hash_algo_ptr_by_offset(uint32_t algo)
 	return &hash_algos[algo];
 }
 
+struct git_hash_ctx *git_hash_alloc(void)
+{
+	return malloc(sizeof(struct git_hash_ctx));
+}
+
+void git_hash_free(struct git_hash_ctx *ctx)
+{
+	free(ctx);
+}
+
+void git_hash_init(struct git_hash_ctx *ctx, const struct git_hash_algo *algop)
+{
+	algop->init_fn(ctx);
+}
+
+void git_hash_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
+{
+	src->algop->clone_fn(dst, src);
+}
+
+void git_hash_update(struct git_hash_ctx *ctx, const void *in, size_t len)
+{
+	ctx->algop->update_fn(ctx, in, len);
+}
+
+void git_hash_final(unsigned char *hash, struct git_hash_ctx *ctx)
+{
+	ctx->algop->final_fn(hash, ctx);
+}
+
+void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
+{
+	ctx->algop->final_oid_fn(oid, ctx);
+}
+
 uint32_t hash_algo_by_name(const char *name)
 {
 	if (!name)

hash.h

@@ -320,27 +320,14 @@ struct git_hash_algo {
 };
 extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];
 
-static inline void git_hash_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
-{
-	src->algop->clone_fn(dst, src);
-}
-
-static inline void git_hash_update(struct git_hash_ctx *ctx, const void *in, size_t len)
-{
-	ctx->algop->update_fn(ctx, in, len);
-}
-
-static inline void git_hash_final(unsigned char *hash, struct git_hash_ctx *ctx)
-{
-	ctx->algop->final_fn(hash, ctx);
-}
-
-static inline void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
-{
-	ctx->algop->final_oid_fn(oid, ctx);
-}
-
+void git_hash_init(struct git_hash_ctx *ctx, const struct git_hash_algo *algop);
+void git_hash_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src);
+void git_hash_update(struct git_hash_ctx *ctx, const void *in, size_t len);
+void git_hash_final(unsigned char *hash, struct git_hash_ctx *ctx);
+void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx);
 const struct git_hash_algo *hash_algo_ptr_by_offset(uint32_t algo);
+struct git_hash_ctx *git_hash_alloc(void);
+void git_hash_free(struct git_hash_ctx *ctx);
 /*
  * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
  * the name doesn't match a known algorithm.