anchor.diff:  
   -export([
            sum_user/2,
  -         sum_bucket/2,
  +         sum_bucket/1,
            make_object/4,
            get_usage/4,
            archive_period/0
  
positive.code: %% The result is a mochijson structure with two fields: `Objects',
  %% which is the number of objects that were counted in the bucket, and
  %% `Bytes', which is the total size of all of those objects.
  -spec sum_bucket(riak_client(), binary()) -> {struct, [{binary(), integer()}]}
                                     | {error, term()}.
  sum_bucket(RcPid, BucketName) ->
      Query = [{map, {modfun, riak_cs_storage, object_size_map},
                [do_prereduce], false},
               {reduce, {modfun, riak_cs_storage, object_size_reduce},
                none, true}],
      ok = riak_cs_riak_client:set_bucket_name(RcPid, BucketName),
      {ok, ManifestPbc} = riak_cs_riak_client:manifest_pbc(RcPid),
      ManifestBucket = riak_cs_utils:to_bucket_name(objects, BucketName),
      case riakc_pb_socket:mapred(ManifestPbc, ManifestBucket, Query) of
          {ok, Results} ->
              {1, [{Objects, Bytes}]} = lists:keyfind(1, 1, Results),
              {struct, [{<<"Objects">>, Objects},
                        {<<"Bytes">>, Bytes}]};
          {error, Error} ->
              {error, Error}
      end.
  
  object_size_map({error, notfound}, _, _) ->
  
negative.code: sum_user(RcPid, User) when is_list(User) ->
      case riak_cs_utils:get_user(User, RcPid) of
          {ok, {?RCS_USER{buckets=Buckets}, _UserObj}} ->
              BucketUsages = [maybe_sum_bucket(User, B) || B <- Buckets],
              {ok, BucketUsages};
          {error, Error} ->
              {error, Error}
  