oidtree: extend iteration to allow for arbitrary return codes

The interface `cb_each()` iterates through a crit-bit tree and calls a
specific callback function for each of the contained items. The callback
function is expected to return either:

  - `CB_CONTINUE` in case iteration shall continue.

  - `CB_BREAK` to abort iteration.

This is needlessly restrictive though, as callers may want to return
arbitrary values and have them be bubbled up to the `cb_each()` call
site. In fact, this is a rather common pattern we have: whenever such a
callback function returns a non-zero error code, we abort iteration and
bubble up the code as-is.

Refactor both the crit-bit tree and oidtree subsystems to behave
accordingly.

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

1 files changed, 9 insertions, 8 deletions

diff --git a/cbtree.h b/cbtree.h
index 43193abdda..c374b1b3db 100644
--- a/cbtree.h
+++ b/cbtree.h
@@ -30,11 +30,6 @@ struct cb_tree {
 	struct cb_node *root;
 };
 
-enum cb_next {
-	CB_CONTINUE = 0,
-	CB_BREAK = 1
-};
-
 #define CBTREE_INIT { 0 }
 
 static inline void cb_init(struct cb_tree *t)
@@ -46,9 +41,15 @@ static inline void cb_init(struct cb_tree *t)
 struct cb_node *cb_lookup(struct cb_tree *, const uint8_t *k, size_t klen);
 struct cb_node *cb_insert(struct cb_tree *, struct cb_node *, size_t klen);
 
-typedef enum cb_next (*cb_iter)(struct cb_node *, void *arg);
+/*
+ * Callback invoked by `cb_each()` for each node in the critbit tree. A return
+ * value of 0 will cause the iteration to continue, a non-zero return code will
+ * cause iteration to abort. The error code will be relayed back from
+ * `cb_each()` in that case.
+ */
+typedef int (*cb_iter)(struct cb_node *, void *arg);
 
-void cb_each(struct cb_tree *, const uint8_t *kpfx, size_t klen,
-		cb_iter, void *arg);
+int cb_each(struct cb_tree *, const uint8_t *kpfx, size_t klen,
+	    cb_iter, void *arg);
 
 #endif /* CBTREE_H */