/*
 * call-seq:
 *     digest_obj.reset -> digest_obj
 *
 * Resets the digest to the initial state and returns self.
 *
 * This method is overridden by each implementation subclass.
 */
static VALUE
rb_digest_instance_reset(VALUE self)
{
    rb_raise(rb_eRuntimeError, "%s does not implement reset()", RSTRING_PTR(rb_inspect(self)));
}