class DownloadChain implements Runnable {

    public long loopFetch() throws IOException {
        if (fetchIndex == fetchInterceptorList.size()) {
            // last one is fetch data interceptor
            fetchIndex--;
        }
        return processFetch();
    }

    private  DownloadChain(int blockIndex, @NonNull DownloadTask task, @NonNull BreakpointInfo info,
                          @NonNull DownloadCache cache, @NonNull DownloadStore store);

}