object-file: move loose object cache into loose source

Our loose objects use a cache that (optionally) stores all objects for
each of the opened sharding directories. This cache is located in the
`struct odb_source`, but now that we have `struct odb_source_loose` it
makes sense to move it into the latter structure so that all state that
relates to loose objects is entirely self-contained.

Do so. While at it, rename corresponding functions to have a prefix that
relates to `struct odb_source_loose`.

Note that despite this prefix, the functions still accept a `struct
odb_source` as input. This is done intentionally: once we introduce
pluggable object databases, we will continue to accept this struct but
then do a cast inside these functions to `struct odb_source_loose`. This
design is similar to how we do it for our ref backends.

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

1 files changed, 14 insertions, 2 deletions

diff --git a/object-file.h b/object-file.h
index 695a7e8e7c..90da69cf5f 100644
--- a/object-file.h
+++ b/object-file.h
@@ -20,6 +20,18 @@ struct odb_source;
 
 struct odb_source_loose {
 	struct odb_source *source;
+
+	/*
+	 * Used to store the results of readdir(3) calls when we are OK
+	 * sacrificing accuracy due to races for speed. That includes
+	 * object existence with OBJECT_INFO_QUICK, as well as
+	 * our search for unique abbreviated hashes. Don't use it for tasks
+	 * requiring greater accuracy!
+	 *
+	 * Be sure to call odb_load_loose_cache() before using.
+	 */
+	uint32_t subdir_seen[8]; /* 256 bits */
+	struct oidtree *cache;
 };
 
 struct odb_source_loose *odb_source_loose_new(struct odb_source *source);
@@ -29,8 +41,8 @@ void odb_source_loose_free(struct odb_source_loose *loose);
  * Populate and return the loose object cache array corresponding to the
  * given object ID.
  */
-struct oidtree *odb_loose_cache(struct odb_source *source,
-				const struct object_id *oid);
+struct oidtree *odb_source_loose_cache(struct odb_source *source,
+				       const struct object_id *oid);
 
 /* Empty the loose object cache for the specified object directory. */
 void odb_clear_loose_cache(struct odb_source *source);