[PATCH v2 3/4] loose: lift loose object index writing logic into helper

[Justin Tobler <jltobler@gmail.com>]

Writing the in-memory loose object map to a "loose-object-idx" file is
handled via `repo_write_loose_object_map()`, which always writes the map
into the primary object directory. In a subsequent commit, a separate
"loose-object-idx" file is staged prior to commit and must be
constructed from a loose object map not attached to the primary loose
object source.

Extract the logic for writing a loose object index file into a separate
`loose_object_map_write()` helper function that allows callers to
explicitly specify both the loose object map as well as the file
descriptor to write the entries to.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
---
 loose.c | 69 +++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 45 insertions(+), 24 deletions(-)

diff --git a/loose.c b/loose.c
index 5f72c644f9..f2e111c25e 100644
--- a/loose.c
+++ b/loose.c
@@ -146,25 +146,17 @@ int repo_read_loose_object_map(struct repository *repo)
 	return 0;
 }
 
-int repo_write_loose_object_map(struct repository *repo)
+static int loose_object_map_write(struct repository *repo,
+				  struct loose_object_map *loose_map, int fd)
 {
-	struct odb_source_files *files = odb_source_files_downcast(repo->objects->source);
-	kh_oid_map_t *map = files->dirs->loose->map->to_compat;
-	struct lock_file lock;
-	int fd;
+	kh_oid_map_t *map = loose_map->to_compat;
+	struct strbuf buf = STRBUF_INIT;
 	khiter_t iter;
-	struct strbuf buf = STRBUF_INIT, path = STRBUF_INIT;
-
-	if (!should_use_loose_object_map(repo))
-		return 0;
+	int ret = -1;
 
-	repo_common_path_replace(repo, &path, "objects/loose-object-idx");
-	fd = repo_hold_lock_file_for_update_timeout(repo, &lock, path.buf,
-						    LOCK_DIE_ON_ERROR,
-						    LOOSE_OBJECT_IDX_LOCK_TIMEOUT_MS);
 	iter = kh_begin(map);
 	if (write_in_full(fd, loose_object_header, strlen(loose_object_header)) < 0)
-		goto errout;
+		goto out;
 
 	for (; iter != kh_end(map); iter++) {
 		if (kh_exist(map, iter)) {
@@ -173,24 +165,53 @@ int repo_write_loose_object_map(struct repository *repo)
 				continue;
 			strbuf_addf(&buf, "%s %s\n", oid_to_hex(&kh_key(map, iter)), oid_to_hex(kh_value(map, iter)));
 			if (write_in_full(fd, buf.buf, buf.len) < 0)
-				goto errout;
+				goto out;
 			strbuf_reset(&buf);
 		}
 	}
+
+	ret = 0;
+
+out:
 	strbuf_release(&buf);
+
+	return ret;
+}
+
+int repo_write_loose_object_map(struct repository *repo)
+{
+	struct odb_source_files *files = odb_source_files_downcast(repo->objects->source);
+	struct strbuf path = STRBUF_INIT;
+	struct lock_file lock;
+	int ret;
+	int fd;
+
+	if (!should_use_loose_object_map(repo))
+		return 0;
+
+	repo_common_path_replace(repo, &path, "objects/loose-object-idx");
+	fd = repo_hold_lock_file_for_update_timeout(repo, &lock, path.buf,
+						    LOCK_DIE_ON_ERROR,
+						    LOOSE_OBJECT_IDX_LOCK_TIMEOUT_MS);
+
+	if (loose_object_map_write(repo, files->dirs->loose->map, fd) < 0) {
+		ret = error_errno(_("unable to write %s"),
+				  get_lock_file_path(&lock));
+		goto out;
+	}
+
 	if (commit_lock_file(&lock) < 0) {
-		error_errno(_("could not write loose object index %s"), path.buf);
-		strbuf_release(&path);
-		return -1;
+		ret = error_errno(_("unable to write %s"), path.buf);
+		goto out;
 	}
-	strbuf_release(&path);
-	return 0;
-errout:
+
+	ret = 0;
+
+out:
 	rollback_lock_file(&lock);
-	strbuf_release(&buf);
-	error_errno(_("failed to write loose object index %s"), path.buf);
 	strbuf_release(&path);
-	return -1;
+
+	return ret;
 }
 
 static int write_one_object(struct odb_source_loose *loose,
-- 
2.56.0.173.gf57c9a7388