{"ast_node_type":"function","tokens":[{"end":98,"kind":"keyword","start":0,"text":"unsafe"}]}
    unsafe extern "C" fn callback(state: *mut c_void, symbol_name: *const c_char) -> *mut c_void {
        let f = unsafe { &mut *(state as *mut &mut dyn FnMut(&[u8]) -> io::Result<()>) };