anchor.diff:  
   -include("basho_bench.hrl").
   
  --define(ETS_TBL_SOURCE_VALUE, 'bb_src_val').
   
   %% ====================================================================
   %% API
  
positive.code:     case SourceSz - BlockSize > 0 of
          true ->
              Offset = random:uniform(SourceSz - BlockSize),
              [Source|_]= ets:lookup(?ETS_TBL_SOURCE_VALUE, key),
              <<_:Offset/bytes, Slice:BlockSize/bytes, _Rest/binary>> = Source,
              Slice;
          false ->
              ?WARN("~p is too small ~p < ~p\n",
                    [SourceCfg, SourceSz, BlockSize]),
              [Source|_]= ets:lookup(?ETS_TBL_SOURCE_VALUE, key),
              Source
      end.
  
negative.code: init_source(Id, undefined) ->
      SourceSz = basho_bench_config:get(?VAL_GEN_SRC_SIZE, 1048576),
      if Id == 1 -> 
              ?DEBUG("random source\n", []);
              %Tid = ets:new(?ETS_TBL_SOURCE_VALUE, [{read_concurrency, true}]),
              %Source = crypto:rand_bytes(SourceSz),
              %ets:insert(Tid, {key, Source});
         true    -> ok
      end,
      {?VAL_GEN_SRC_SIZE, SourceSz};
  init_source(Id, Path) ->
      {Path, {ok, Bin}} = {Path, file:read_file(Path)},
      if Id == 1 -> 
              ?DEBUG("path source ~p ~p\n", [size(Bin), Path]);
              %Tid = ets:new(?ETS_TBL_SOURCE_VALUE, [{read_concurrency, true}]),
              %ets:insert(Tid, {key, Bin});
         true    -> ok
      end,
      {?VAL_GEN_BLOB_CFG, size(Bin)}.
  