open Printf

let iterations = 10000;;

(*===================================================================================*)
let rec read_loop str x acc intbits bitind =                                     (*1*)
  if x <= intbits                                                                (*2*)
  then
    (acc lsr (intbits-x))                                                        (*3*)
  else
    read_loop str x ((int_of_char (str.[bitind]) ) lor (acc lsl 8))              (*4*) 
              (intbits+8) (bitind+1);;                                           (*5*)
    
let get_xbits str x inoff =                                                      (*6*)
  let bitoff = (inoff land 7)                                                    (*7*)
  and bitind = (inoff lsr 3)                                                     (*8*)
  in
  let intbits = 8-bitoff in                                                      (*9*)
  let res = (int_of_char (str.[bitind])) land ((1 lsl intbits)-1) in             (*10*)
  read_loop str x res intbits (bitind+1);;                                       (*11*)

let skip_bits nofchannels =                                                      (*12*)
  (((5 + (nofchannels * 11) - 1) lsr 3)+1) * 8;;                                 (*13*)

let rec getchannels str offset nofchannels =                                     (*14*)
  if nofchannels > 0                                                             (*15*)
  then
    (get_xbits str 11 offset) :: getchannels str (offset+11) (nofchannels-1)     (*16*)
  else
    [];;                                                                         (*17*)

let rec decode_five_11 str nofpackets offset =                                   (*18*)
  if nofpackets > 0                                                              (*19*)
  then
    let nofchannels = get_xbits str 5 offset                                     (*20*)
    in
    let list = getchannels str (offset+5) nofchannels in                         (*21*)
    list :: (decode_five_11 str (nofpackets-1) (offset+(skip_bits nofchannels))) (*22*)
  else
    [];;                                                                         (*23*)

(*===================================================================================*)

let rec sum l =
   match l with
      (a::b) -> a + (sum b)
   |  [] -> 0;;

let rec sumlists l =
    match l with
      (a::b) -> ((sum a) + (sumlists b))
    | [] -> 0;;

let get_file fname = 
  let handle = open_in fname
  in
  let  len = (in_channel_length handle); 
  in
  let s = String.create len 
  in
  (really_input handle s 0 len;
   s);;

let rec iter n f =
  if n>1
  then
    (f(); iter (n-1) f)
  else
    f();;

let main fname =    
  let str = get_file fname
  in
  let packets=(get_xbits str 16 0) 
  in
  let start = Sys.time() in
  let sumval = (iter iterations (function () -> 
    sumlists (decode_five_11 str packets 16))) 
  in
  let stop = Sys.time () in
  let time = (stop -. start) in
  let outfile = open_out (fname ^ ".ocaml") in
  (output_string outfile (string_of_int sumval);
   printf "%.3f" time;
   flush stdout);; 
 
let () = 
  let w = (Array.get Sys.argv 1) in
  main w;;