[PATCH 2/2] oidmap: rework iterators to return typed pointer

[Abhishek Kumar <abhishekkumar8222@gmail.com>]

87571c3 modified hashmap_iter_next to return a hashmap_entry pointer
instead of void pointer.

However, oidmap_iter_next is unaware of the struct type containing
oidmap_entry and explicilty returns a void pointer.

Rework oidmap_iter_* to include struct type and return appropriate
pointer. This allows for compile-time type checks.

Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com>
---
 oidmap.h               | 27 +++++++++++++++------------
 t/helper/test-oidmap.c |  2 +-
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/oidmap.h b/oidmap.h
index c66a83ab1d..5d6b34a7ce 100644
--- a/oidmap.h
+++ b/oidmap.h
@@ -76,18 +76,21 @@ static inline void oidmap_iter_init(struct oidmap *map, struct oidmap_iter *iter
 	hashmap_iter_init(&map->map, &iter->h_iter);
 }
 
-static inline void *oidmap_iter_next(struct oidmap_iter *iter)
-{
-	/* TODO: this API could be reworked to do compile-time type checks */
-	return (void *)hashmap_iter_next(&iter->h_iter);
-}
+/*
+ * Returns the next entry, or NULL if there are no more entries.
+ *
+ * The entry is of @type (e.g. "struct foo") and has a member of type struct
+ * oidmap_entry.
+ */
+#define oidmap_iter_next(iter, type) \
+	(type *) hashmap_iter_next(&(iter)->h_iter)
 
-static inline void *oidmap_iter_first(struct oidmap *map,
-				      struct oidmap_iter *iter)
-{
-	oidmap_iter_init(map, iter);
-	/* TODO: this API could be reworked to do compile-time type checks */
-	return (void *)oidmap_iter_next(iter);
-}
+/*
+ * Returns the first entry in @map using @iter, where the entry is of @type
+ * (e.g. "struct foo") and has a member of type struct oidmap_entry.
+ */
+#define oidmap_iter_first(map, iter, type) \
+	({oidmap_iter_init(map, iter); \
+	 oidmap_iter_next(iter, type); })
 
 #endif
diff --git a/t/helper/test-oidmap.c b/t/helper/test-oidmap.c
index 0acf99931e..a28bf007a8 100644
--- a/t/helper/test-oidmap.c
+++ b/t/helper/test-oidmap.c
@@ -96,7 +96,7 @@ int cmd__oidmap(int argc, const char **argv)
 
 			struct oidmap_iter iter;
 			oidmap_iter_init(&map, &iter);
-			while ((entry = oidmap_iter_next(&iter)))
+			while ((entry = oidmap_iter_next(&iter, struct test_entry)))
 				printf("%s %s\n", oid_to_hex(&entry->entry.oid), entry->name);
 
 		} else {
-- 
2.26.0