anchor.diff:  state(#http{is=chunk_data}) -> payload;
   state(#http{is=chunk_tail}) -> payload;
   state(#http{is=eoh})     -> eoh;
  -state(#http{is=eof})     -> eof.
  +state(#http{is=eof})     -> eof;
  +state(#http{is=upgrade}) -> upgrade.
   
   %%
   %% return version of http stream
  
positive.code: %%    (Not implemented)
  %%
  %% 5. By the server closing the connection. 
  decode_check_payload(#http{htline={'GET',  _}}=S) ->
     S#http{is=eof};
  decode_check_payload(#http{htline={'HEAD', _}}=S) ->
     S#http{is=eof};
  decode_check_payload(#http{htline={'DELETE', _}}=S) ->
  
negative.code: 
  %%
  %% check parser state
  %%   idle    - 
  %%   header  - handling headers
  %%   payload - handling payload
  %%   eoh     - end of headers
  %%   eof     - end of message  
  %%   upgrade - upgrade is requested
  -spec(state/1 :: (#http{}) -> idle | header | payload | eof | upgrade).
  
  state(#http{is=idle})    -> idle;
  state(#http{is=header})  -> header;
  