odb: introduce `odb_for_each_object()`

Introduce a new function `odb_for_each_object()` that knows to iterate
through all objects part of a given object database. This function is
essentially a simple wrapper around the object database sources.

Subsequent commits will adapt callers to use this new function.

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

1 files changed, 20 insertions, 0 deletions

diff --git a/odb.h b/odb.h
index f97f249580..b5d28bc188 100644
--- a/odb.h
+++ b/odb.h
@@ -475,6 +475,26 @@ typedef int (*odb_for_each_object_cb)(const struct object_id *oid,
 				      struct object_info *oi,
 				      void *cb_data);
 
+/*
+ * Iterate through all objects contained in the object database. Note that
+ * objects may be iterated over multiple times in case they are either stored
+ * in different backends or in case they are stored in multiple sources.
+ * If an object info request is given, then the object info will be read and
+ * passed to the callback as if `odb_read_object_info()` was called for the
+ * object.
+ *
+ * Returning a non-zero error code from the callback function will cause
+ * iteration to abort. The error code will be propagated.
+ *
+ * Returns 0 on success, a negative error code in case a failure occurred, or
+ * an arbitrary non-zero error code returned by the callback itself.
+ */
+int odb_for_each_object(struct object_database *odb,
+			const struct object_info *request,
+			odb_for_each_object_cb cb,
+			void *cb_data,
+			unsigned flags);
+
 enum {
 	/*
 	 * By default, `odb_write_object()` does not actually write anything