require 'mkmf'
create_header
create_makefile 'name_of_c_file'
#include "ruby.h"
#include "extconf.h"
// VALUE is ruby type
// define c function
// define init function
void Init_mod_name() {
VALUE mod = rb_define_module("module_name");
rb_define_method(mod, "method_name", function, arg_count);
}
ruby extconf.rb
make
require './module.so/bundle'
include ModuleName
method_name(args)