add generic, type aware object chain walker

The requirements are:
* it may not crash on NULL pointers
* a callback function is needed, as index-pack/unpack-objects
  need to do different things
* the type information is needed to check the expected <-> real type
  and print better error messages

Signed-off-by: Martin Koegler <mkoegler@auto.tuwien.ac.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/fsck.h b/fsck.h
new file mode 100644
index 000000000..ba5514a81
--- /dev/null
+++ b/fsck.h
@@ -0,0 +1,23 @@
+#ifndef GIT_FSCK_H
+#define GIT_FSCK_H
+
+/*
+ * callback function for fsck_walk
+ * type is the expected type of the object or OBJ_ANY
+ * the return value is:
+ *     0	everything OK
+ *     <0	error signaled and abort
+ *     >0	error signaled and do not abort
+ */
+typedef int (*fsck_walk_func)(struct object *obj, int type, void *data);
+
+/* descend in all linked child objects
+ * the return value is:
+ *    -1	error in processing the object
+ *    <0	return value of the callback, which lead to an abort
+ *    >0	return value of the first sigaled error >0 (in the case of no other errors)
+ *    0		everything OK
+ */
+int fsck_walk(struct object *obj, fsck_walk_func walk, void *data);
+
+#endif