object-store: factor out odb_loose_cache()

Add and use a function for loading the entries of a loose object
subdirectory for a given object ID.  It frees callers from deriving the
fanout key; they can use the returned oid_array reference for lookups or
forward range scans.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object-store.h

@@ -54,6 +54,13 @@ void add_to_alternates_memory(const char *dir);
  */
 void odb_load_loose_cache(struct object_directory *odb, int subdir_nr);
 
+/*
+ * Populate and return the loose object cache array corresponding to the
+ * given object ID.
+ */
+struct oid_array *odb_loose_cache(struct object_directory *odb,
+				  const struct object_id *oid);
+
 struct packed_git {
 	struct packed_git *next;
 	struct list_head mru;

sha1-file.c

@@ -924,7 +924,6 @@ static int open_sha1_file(struct repository *r,
 static int quick_has_loose(struct repository *r,
 			   const unsigned char *sha1)
 {
-	int subdir_nr = sha1[0];
 	struct object_id oid;
 	struct object_directory *odb;
 
@@ -932,8 +931,7 @@ static int quick_has_loose(struct repository *r,
 
 	prepare_alt_odb(r);
 	for (odb = r->objects->odb; odb; odb = odb->next) {
-		odb_load_loose_cache(odb, subdir_nr);
-		if (oid_array_lookup(&odb->loose_objects_cache, &oid) >= 0)
+		if (oid_array_lookup(odb_loose_cache(odb, &oid), &oid) >= 0)
 			return 1;
 	}
 	return 0;
@@ -2152,6 +2150,14 @@ static int append_loose_object(const struct object_id *oid, const char *path,
 	return 0;
 }
 
+struct oid_array *odb_loose_cache(struct object_directory *odb,
+				  const struct object_id *oid)
+{
+	int subdir_nr = oid->hash[0];
+	odb_load_loose_cache(odb, subdir_nr);
+	return &odb->loose_objects_cache;
+}
+
 void odb_load_loose_cache(struct object_directory *odb, int subdir_nr)
 {
 	struct strbuf buf = STRBUF_INIT;

sha1-name.c

@@ -87,21 +87,21 @@ static int match_sha(unsigned, const unsigned char *, const unsigned char *);
 
 static void find_short_object_filename(struct disambiguate_state *ds)
 {
-	int subdir_nr = ds->bin_pfx.hash[0];
 	struct object_directory *odb;
 
 	for (odb = the_repository->objects->odb;
 	     odb && !ds->ambiguous;
 	     odb = odb->next) {
 		int pos;
+		struct oid_array *loose_objects;
 
-		odb_load_loose_cache(odb, subdir_nr);
-		pos = oid_array_lookup(&odb->loose_objects_cache, &ds->bin_pfx);
+		loose_objects = odb_loose_cache(odb, &ds->bin_pfx);
+		pos = oid_array_lookup(loose_objects, &ds->bin_pfx);
 		if (pos < 0)
 			pos = -1 - pos;
-		while (!ds->ambiguous && pos < odb->loose_objects_cache.nr) {
+		while (!ds->ambiguous && pos < loose_objects->nr) {
 			const struct object_id *oid;
-			oid = odb->loose_objects_cache.oid + pos;
+			oid = loose_objects->oid + pos;
 			if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
 				break;
 			update_candidates(ds, oid);