commit-graph: store the hash algorithm instead of its length

The commit-graph stores the length of the hash algorithm it uses. In
subsequent commits we'll need to pass the whole hash algorithm around
though, which we currently don't have access to.

Refactor the code so that we store the hash algorithm instead of only
its size.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

commit-graph.c

@@ -312,7 +312,7 @@ static int graph_read_oid_lookup(const unsigned char *chunk_start,
 {
 	struct commit_graph *g = data;
 	g->chunk_oid_lookup = chunk_start;
-	if (chunk_size / g->hash_len != g->num_commits)
+	if (chunk_size / g->hash_algo->rawsz != g->num_commits)
 		return error(_("commit-graph OID lookup chunk is the wrong size"));
 	return 0;
 }
@@ -414,7 +414,7 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
 
 	graph = alloc_commit_graph();
 
-	graph->hash_len = the_hash_algo->rawsz;
+	graph->hash_algo = the_hash_algo;
 	graph->num_chunks = *(unsigned char*)(data + 6);
 	graph->data = graph_map;
 	graph->data_len = graph_size;
@@ -479,7 +479,7 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
 		FREE_AND_NULL(graph->bloom_filter_settings);
 	}
 
-	oidread(&graph->oid, graph->data + graph->data_len - graph->hash_len,
+	oidread(&graph->oid, graph->data + graph->data_len - graph->hash_algo->rawsz,
 		the_repository->hash_algo);
 
 	free_chunkfile(cf);
@@ -585,7 +585,7 @@ static int add_graph_to_chain(struct commit_graph *g,
 		return 0;
 	}
 
-	if (g->chunk_base_graphs_size / g->hash_len < n) {
+	if (g->chunk_base_graphs_size / g->hash_algo->rawsz < n) {
 		warning(_("commit-graph base graphs chunk is too small"));
 		return 0;
 	}
@@ -595,7 +595,7 @@ static int add_graph_to_chain(struct commit_graph *g,
 
 		if (!cur_g ||
 		    !oideq(&oids[n], &cur_g->oid) ||
-		    !hasheq(oids[n].hash, g->chunk_base_graphs + st_mult(g->hash_len, n),
+		    !hasheq(oids[n].hash, g->chunk_base_graphs + st_mult(g->hash_algo->rawsz, n),
 			    the_repository->hash_algo)) {
 			warning(_("commit-graph chain does not match"));
 			return 0;
@@ -806,7 +806,7 @@ int generation_numbers_enabled(struct repository *r)
 		return 0;
 
 	first_generation = get_be32(g->chunk_commit_data +
-				    g->hash_len + 8) >> 2;
+				    g->hash_algo->rawsz + 8) >> 2;
 
 	return !!first_generation;
 }
@@ -850,7 +850,7 @@ void close_commit_graph(struct object_database *o)
 static int bsearch_graph(struct commit_graph *g, const struct object_id *oid, uint32_t *pos)
 {
 	return bsearch_hash(oid->hash, g->chunk_oid_fanout,
-			    g->chunk_oid_lookup, g->hash_len, pos);
+			    g->chunk_oid_lookup, g->hash_algo->rawsz, pos);
 }
 
 static void load_oid_from_graph(struct commit_graph *g,
@@ -870,7 +870,7 @@ static void load_oid_from_graph(struct commit_graph *g,
 
 	lex_index = pos - g->num_commits_in_base;
 
-	oidread(oid, g->chunk_oid_lookup + st_mult(g->hash_len, lex_index),
+	oidread(oid, g->chunk_oid_lookup + st_mult(g->hash_algo->rawsz, lex_index),
 		the_repository->hash_algo);
 }
 
@@ -912,8 +912,8 @@ static void fill_commit_graph_info(struct commit *item, struct commit_graph *g,
 	graph_data = commit_graph_data_at(item);
 	graph_data->graph_pos = pos;
 
-	date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
-	date_low = get_be32(commit_data + g->hash_len + 12);
+	date_high = get_be32(commit_data + g->hash_algo->rawsz + 8) & 0x3;
+	date_low = get_be32(commit_data + g->hash_algo->rawsz + 12);
 	item->date = (timestamp_t)((date_high << 32) | date_low);
 
 	if (g->read_generation_data) {
@@ -931,10 +931,10 @@ static void fill_commit_graph_info(struct commit *item, struct commit_graph *g,
 		} else
 			graph_data->generation = item->date + offset;
 	} else
-		graph_data->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
+		graph_data->generation = get_be32(commit_data + g->hash_algo->rawsz + 8) >> 2;
 
 	if (g->topo_levels)
-		*topo_level_slab_at(g->topo_levels, item) = get_be32(commit_data + g->hash_len + 8) >> 2;
+		*topo_level_slab_at(g->topo_levels, item) = get_be32(commit_data + g->hash_algo->rawsz + 8) >> 2;
 }
 
 static inline void set_commit_tree(struct commit *c, struct tree *t)
@@ -958,20 +958,20 @@ static int fill_commit_in_graph(struct repository *r,
 	fill_commit_graph_info(item, g, pos);
 
 	lex_index = pos - g->num_commits_in_base;
-	commit_data = g->chunk_commit_data + st_mult(g->hash_len + 16, lex_index);
+	commit_data = g->chunk_commit_data + st_mult(g->hash_algo->rawsz + 16, lex_index);
 
 	item->object.parsed = 1;
 
 	set_commit_tree(item, NULL);
 
 	pptr = &item->parents;
 
-	edge_value = get_be32(commit_data + g->hash_len);
+	edge_value = get_be32(commit_data + g->hash_algo->rawsz);
 	if (edge_value == GRAPH_PARENT_NONE)
 		return 1;
 	pptr = insert_parent_or_die(r, g, edge_value, pptr);
 
-	edge_value = get_be32(commit_data + g->hash_len + 4);
+	edge_value = get_be32(commit_data + g->hash_algo->rawsz + 4);
 	if (edge_value == GRAPH_PARENT_NONE)
 		return 1;
 	if (!(edge_value & GRAPH_EXTRA_EDGES_NEEDED)) {
@@ -2624,7 +2624,7 @@ int write_commit_graph(struct odb_source *source,
 		struct commit_graph *g = ctx.r->objects->commit_graph;
 		for (i = 0; i < g->num_commits; i++) {
 			struct object_id oid;
-			oidread(&oid, g->chunk_oid_lookup + st_mult(g->hash_len, i),
+			oidread(&oid, g->chunk_oid_lookup + st_mult(g->hash_algo->rawsz, i),
 				the_repository->hash_algo);
 			oid_array_append(&ctx.oids, &oid);
 		}
@@ -2755,7 +2755,7 @@ static int verify_one_commit_graph(struct repository *r,
 	for (i = 0; i < g->num_commits; i++) {
 		struct commit *graph_commit;
 
-		oidread(&cur_oid, g->chunk_oid_lookup + st_mult(g->hash_len, i),
+		oidread(&cur_oid, g->chunk_oid_lookup + st_mult(g->hash_algo->rawsz, i),
 			the_repository->hash_algo);
 
 		if (i && oidcmp(&prev_oid, &cur_oid) >= 0)
@@ -2800,7 +2800,7 @@ static int verify_one_commit_graph(struct repository *r,
 		timestamp_t generation;
 
 		display_progress(progress, ++(*seen));
-		oidread(&cur_oid, g->chunk_oid_lookup + st_mult(g->hash_len, i),
+		oidread(&cur_oid, g->chunk_oid_lookup + st_mult(g->hash_algo->rawsz, i),
 			the_repository->hash_algo);
 
 		graph_commit = lookup_commit(r, &cur_oid);

commit-graph.h

@@ -84,7 +84,7 @@ struct commit_graph {
 	const unsigned char *data;
 	size_t data_len;
 
-	unsigned char hash_len;
+	const struct git_hash_algo *hash_algo;
 	unsigned char num_chunks;
 	uint32_t num_commits;
 	struct object_id oid;