lib: import new JSON iteration macro

Save a few lines when iterating over JSON objects using the new
JSON_FOREACH macro.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

.clang-format

@@ -43,6 +43,7 @@ ForEachMacros:
   - SPLAY_FOREACH
   - FOR_ALL_INTERFACES
   - FOR_ALL_INTERFACES_ADDRESSES
+  - JSON_FOREACH
   # zebra
   - RE_DEST_FOREACH_ROUTE
   - RE_DEST_FOREACH_ROUTE_SAFE

lib/json.h

@@ -23,6 +23,20 @@
 
 #if defined(HAVE_JSON_C_JSON_H)
 #include <json-c/json.h>
+
+/*
+ * FRR style JSON iteration.
+ * Usage: JSON_FOREACH(...) { ... }
+ */
+#define JSON_FOREACH(jo, joi, join)                                            \
+	/* struct json_object *jo; */                                          \
+	/* struct json_object_iterator joi; */                                 \
+	/* struct json_object_iterator join; */                                \
+	for ((joi) = json_object_iter_begin((jo)),                             \
+	    (join) = json_object_iter_end((jo));                               \
+	     json_object_iter_equal(&(joi), &(join)) == 0;                     \
+	     json_object_iter_next(&(joi)))
+
 #else
 #include <json/json.h>