Macro rocket_include_static_resources::static_response_builder

macro_rules! static_response_builder {
    ( $id:expr ) => { ... };
    ( $etag_if_none_match:expr, $id:expr ) => { ... };
}

Used for retrieving the file you input through the macro static_resources_initialize! as a ResponseBuilder instance into which three HTTP headers, Content-Type, Content-Length and Etag, will be automatically added. After fetching the ResponseBuilder instance, you can add extra headers into it!