Add new API `mrb_iv_foreach()` to iterate over instance variables.

include/mruby/variable.h

@@ -131,6 +131,10 @@ void mrb_gc_mark_iv(mrb_state*, struct RObject*);
 size_t mrb_gc_mark_iv_size(mrb_state*, struct RObject*);
 void mrb_gc_free_iv(mrb_state*, struct RObject*);
 
+/* return non zero to break the loop */
+typedef int (iv_foreach_func)(mrb_state*,mrb_sym,mrb_value,void*);
+MRB_API void mrb_iv_foreach(mrb_state *mrb, mrb_value obj, iv_foreach_func *func, void *p);
+
 MRB_END_DECL
 
 #endif  /* MRUBY_VARIABLE_H */

src/variable.c

@@ -9,8 +9,7 @@
 #include <mruby/class.h>
 #include <mruby/proc.h>
 #include <mruby/string.h>
-
-typedef int (iv_foreach_func)(mrb_state*,mrb_sym,mrb_value,void*);
+#include <mruby/variable.h>
 
 #ifndef MRB_IV_SEGMENT_SIZE
 #define MRB_IV_SEGMENT_SIZE 4
@@ -359,6 +358,14 @@ mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
   mrb_write_barrier(mrb, (struct RBasic*)obj);
 }
 
+/* Iterates over the instance variable table. */
+MRB_API void
+mrb_iv_foreach(mrb_state *mrb, mrb_value obj, iv_foreach_func *func, void *p)
+{
+  if (!obj_iv_p(obj)) return;
+  iv_foreach(mrb, mrb_obj_ptr(obj)->iv, func, p);
+}
+
 static inline mrb_bool
 namespace_p(enum mrb_vtype tt)
 {