anchor.diff:                  current_buffer_size=0 :: non_neg_integer(),
                   buffer_queue=[] :: [binary()], %% not actually a queue, but we treat it like one
                   remainder_data :: undefined | binary(),
  -                free_writers :: ordsets:ordset(pid()),
  +                free_writers :: undefined | ordsets:ordset(pid()),
                   unacked_writes=ordsets:new() :: ordsets:ordset(non_neg_integer()),
                   next_block_id=0 :: non_neg_integer(),
                   all_writer_pids=[] :: list(pid())}).
  
positive.code:                 caller :: reference(),
                  md5 :: binary(),
                  reply_pid :: {pid(), reference()},
                  mani_pid :: pid(),
                  riakc_pid :: pid(),
                  timer_ref :: reference(),
                  bucket :: binary(),
  
negative.code: %%--------------------------------------------------------------------
  terminate(_Reason, _StateName, #state{mani_pid=ManiPid,
                                        all_writer_pids=BlockServerPids}) ->
      maybe_stop_manifest_fsm(ManiPid),
      maybe_stop_block_servers(BlockServerPids),
      ok.
  
  %%--------------------------------------------------------------------
  