object-store: migrate alternates struct and functions from cache.h

Migrate the struct alternate_object_database and all its related
functions to the object store as these functions are easier found in
that header. The migration is just a verbatim copy, no need to
include the object store header at any C file, because cache.h includes
repository.h which in turn includes the object-store.h

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/object-store.h b/object-store.h
index abfaae0..5002e37 100644
--- a/object-store.h
+++ b/object-store.h
@@ -1,6 +1,57 @@
 #ifndef OBJECT_STORE_H
 #define OBJECT_STORE_H
 
+extern struct alternate_object_database {
+	struct alternate_object_database *next;
+
+	/* see alt_scratch_buf() */
+	struct strbuf scratch;
+	size_t base_len;
+
+	/*
+	 * Used to store the results of readdir(3) calls when searching
+	 * for unique abbreviated hashes.  This cache is never
+	 * invalidated, thus it's racy and not necessarily accurate.
+	 * That's fine for its purpose; don't use it for tasks requiring
+	 * greater accuracy!
+	 */
+	char loose_objects_subdir_seen[256];
+	struct oid_array loose_objects_cache;
+
+	char path[FLEX_ARRAY];
+} *alt_odb_list;
+void prepare_alt_odb(void);
+char *compute_alternate_path(const char *path, struct strbuf *err);
+typedef int alt_odb_fn(struct alternate_object_database *, void *);
+int foreach_alt_odb(alt_odb_fn, void*);
+
+/*
+ * Allocate a "struct alternate_object_database" but do _not_ actually
+ * add it to the list of alternates.
+ */
+struct alternate_object_database *alloc_alt_odb(const char *dir);
+
+/*
+ * Add the directory to the on-disk alternates file; the new entry will also
+ * take effect in the current process.
+ */
+void add_to_alternates_file(const char *dir);
+
+/*
+ * Add the directory to the in-memory list of alternates (along with any
+ * recursive alternates it points to), but do not modify the on-disk alternates
+ * file.
+ */
+void add_to_alternates_memory(const char *dir);
+
+/*
+ * Returns a scratch strbuf pre-filled with the alternate object directory,
+ * including a trailing slash, which can be used to access paths in the
+ * alternate. Always use this over direct access to alt->scratch, as it
+ * cleans up any previous use of the scratch buffer.
+ */
+struct strbuf *alt_scratch_buf(struct alternate_object_database *alt);
+
 struct raw_object_store {
 	/*
 	 * Path to the repository's object store.