Function safe_app::ffi::mutable_data::mdata_serialised_size

#[no_mangle]
pub unsafe extern "C" fn mdata_serialised_size(
    app: *const App, 
    info: *const MDataInfo, 
    user_data: *mut c_void, 
    o_cb: extern "C" fn(user_data: *mut c_void, result: *const FfiResult, serialised_size: u64)
)

Get size of serialised mutable data.