Function uv_fs_sendfile 

pub unsafe extern "C" fn uv_fs_sendfile(
    loop_: *mut uv_loop_t,
    req: *mut uv_fs_t,
    out_fd: uv_file,
    in_fd: uv_file,
    in_offset: i64,
    length: size_t,
    cb: uv_fs_cb,
) -> c_int