open Printf

let iterations = 100;;

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

let build_byte_triplet instr index = 						(*1*)
  let a = int_of_char instr.[index]						(*2*)
  and b = int_of_char instr.[index+1]						(*3*)
  and c = int_of_char instr.[index+2]						(*4*)
  and d = int_of_char instr.[index+3]						(*5*)
  in
  (((a-32) lsl 18) lor (((b-32) lsl 12)  lor (((c-32) lsl 6) lor (d-32))));;	(*6*)

let build_byte_duo instr index =						(*7*)
  let a = int_of_char instr.[index]						(*8*)
  and b = int_of_char instr.[index+1]						(*9*)
  and c = int_of_char instr.[index+2]						(*10*)
  in
  (((a-32) lsl 10) lor (((b-32) lsl 4)  lor (((c-32) land 15))));;		(*11*)

let build_byte instr index = 							(*12*)
  let a = int_of_char instr.[index]						(*13*)
  and b = int_of_char instr.[index+1]						(*14*)
  in
  (((a-32) lsl 2) lor ((b-32) land 3))						(*15*)

let put_triplet str index triplet =						(*16*)
  (str.[index] <- char_of_int ((triplet lsl 16) land 255) ;			(*17*)
   str.[index+1] <- char_of_int ((triplet lsl 8) land 255);			(*18*)
   str.[index+2] <- char_of_int (triplet land 255));;				(*19*)

let put_duo str index duo =							(*20*)
  (str.[index] <- char_of_int ((duo lsl 8) land 255);				(*21*)
   str.[index+1] <- char_of_int (duo land 255));;				(*22*)

let put_byte str index byte =							(*23*)
  str.[index] <- char_of_int (byte land 255);;					(*24*)

let get_nof_octets instr index =						(*25*)
  (int_of_char instr.[index]) - 32;;						(*26*)

let check_postamble instr inoff acc =						(*27*)
  if (String.sub instr inoff 4) == "\nend"					(*28*)
  then
    String.concat "" (List.rev acc)						(*29*)
  else
    String.concat "" (List.rev acc);;						(*30*)

let rec uudecode_line instr outstr inoff outoff nof_octets acc =		(*31*)
  if nof_octets>=3								(*32*)
  then
    (put_triplet outstr outoff (build_byte_triplet instr inoff);		(*33*)
     uudecode_line instr outstr (inoff+4) (outoff+3) (nof_octets-3) acc)	(*34*)
  else
    if nof_octets==0								(*35*)
    then
      skip_to_next_line instr inoff (outstr::acc)				(*36*)
    else
      if nof_octets==1								(*37*)
      then
	(put_byte outstr outoff (build_byte instr inoff);			(*38*)
	 skip_to_next_line instr (inoff+4) (outstr::acc))			(*39*)
      else
	(put_duo outstr outoff (build_byte_duo instr inoff);			(*40*)
	 skip_to_next_line instr (inoff+4) (outstr::acc))			(*41*)
and uudecode_lines instr inoff acc =						(*42*)
  let nof_octets = ((int_of_char instr.[inoff]) - 32)				(*43*)
  in
  if nof_octets == 0								(*44*)
  then
    check_postamble instr (inoff+1) acc						(*45*)
  else
    uudecode_line instr (String.create nof_octets) (inoff+1) 0 nof_octets acc	(*46*)
and skip_to_next_line instr inoff acc =						(*47*)
  if (int_of_char instr.[inoff]) == 10						(*48*)
  then
    uudecode_lines instr (inoff+1) acc						(*49*)
  else
    skip_to_next_line instr (inoff+1) acc;;					(*50*)
  
let rec get_name str startoff size =						(*51*)
    if (int_of_char str.[startoff+size]) == 32					(*52*)
    then 
      if (int_of_char str.[startoff+size+1]) == 10				(*53*)
      then 
	String.sub str startoff (size)						(*54*)
      else
	get_name str startoff (size+1)						(*55*)
    else
      get_name str startoff (size+1);;						(*56*)

let decode str =								(*57*)
    match String.sub str 0 6 with						(*58*)
      "begin " ->								(*59*)
        let u = int_of_char str.[6]						(*60*)
        and g = int_of_char str.[7]						(*61*)
        and a = int_of_char str.[8]						(*62*)
        and name = get_name str 10 0						(*63*)
        in
        ((u lsl 6) lor ((g lsl 3) lor a), name,					(*64*)
         uudecode_lines str (12 + String.length name) [])			(*65*)
   
(*============================================================================*)
let rec iter n f =
  if n>1
  then
    (f(); iter (n-1) f)
  else
    f();;

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 main inname =    
  let str = get_file inname
  in
  let start = Sys.time() in
  match (iter iterations (function () -> decode str)) with
    (access,name,outstr) ->
      let stop = Sys.time () in
      let time = (stop -. start) in
      let out = open_out_gen [Open_wronly] access name
      in
      (output out outstr 0 (String.length outstr);
       printf "%.3f" time;
       flush stdout) ;; 

let () =
  let infile = (Array.get Sys.argv 1);
  in
  main infile;;