new API function mrb_string_value_len()

include/mruby/string.h

@@ -123,7 +123,8 @@ MRB_API mrb_value mrb_check_string_type(mrb_state *mrb, mrb_value str);
 MRB_API mrb_value mrb_str_buf_new(mrb_state *mrb, size_t capa);
 
 MRB_API const char *mrb_string_value_cstr(mrb_state *mrb, mrb_value *ptr);
-MRB_API const char *mrb_string_value_ptr(mrb_state *mrb, mrb_value ptr);
+MRB_API const char *mrb_string_value_ptr(mrb_state *mrb, mrb_value str);
+MRB_API mrb_int mrb_string_value_len(mrb_state *mrb, mrb_value str);
 
 /*
  * Duplicates a string object.

src/string.c

@@ -1013,6 +1013,13 @@ mrb_string_value_ptr(mrb_state *mrb, mrb_value ptr)
   return RSTRING_PTR(str);
 }
 
+MRB_API mrb_int
+mrb_string_value_len(mrb_state *mrb, mrb_value ptr)
+{
+  mrb_value str = mrb_str_to_str(mrb, ptr);
+  return RSTRING_LEN(str);
+}
+
 void
 mrb_noregexp(mrb_state *mrb, mrb_value self)
 {