gistfile1.txt

module String = StringLabels

type t = Bytes.t

external unsafe_get_64 : Bytes.t -> int -> int64 = "%caml_string_get64u"
external unsafe_set_64 : Bytes.t -> int -> int64 -> unit = "%caml_string_set64u"

let pp_hum fmt t =
  Printf.fprintf fmt "x%.16Lx" (unsafe_get_64 t 0);
  Printf.fprintf fmt "x%.16Lx" (unsafe_get_64 t 8);
  Printf.fprintf fmt "x%.16Lx" (unsafe_get_64 t 16);
  Printf.fprintf fmt "x%.16Lx" (unsafe_get_64 t 24);
;;

let create cs =
  let t = Bytes.make 32 '\000' in
  String.iter cs ~f:(fun char ->
    let code = Char.code char in
    let word = (code lsr 6) lsl 3 in
    unsafe_set_64 t word Int64.(logor (unsafe_get_64 t word) (shift_left 1L code)));
  Printf.printf "create: %a\n%!" pp_hum t;
  t

let member t char =
  let code = Char.code char in
  let word = (code lsr 6) lsl 3 in
  Int64.((logand (unsafe_get_64 t word) (shift_left 1L code)) <> 0L)

let union u v =
  let t = Bytes.make 32 '\000' in
  unsafe_set_64 t 0  Int64.(logor (unsafe_get_64 u 0 ) (unsafe_get_64 v 0 ));
  unsafe_set_64 t 8  Int64.(logor (unsafe_get_64 u 8 ) (unsafe_get_64 v 8 ));
  unsafe_set_64 t 16 Int64.(logor (unsafe_get_64 u 16) (unsafe_get_64 v 16));
  unsafe_set_64 t 24 Int64.(logor (unsafe_get_64 u 24) (unsafe_get_64 v 24));
  t

let difference u v =
  let t = Bytes.make 32 '\000' in
  unsafe_set_64 t 0  Int64.(logand (unsafe_get_64 u 0 ) (lognot (unsafe_get_64 v 0 )));
  unsafe_set_64 t 8  Int64.(logand (unsafe_get_64 u 8 ) (lognot (unsafe_get_64 v 8 )));
  unsafe_set_64 t 16 Int64.(logand (unsafe_get_64 u 16) (lognot (unsafe_get_64 v 16)));
  unsafe_set_64 t 24 Int64.(logand (unsafe_get_64 u 24) (lognot (unsafe_get_64 v 24)));
  t

let negate t =
  Printf.printf "before: %a\n%!" pp_hum t;
  let u = Bytes.make 32 '\000' in
  unsafe_set_64 u 0  Int64.(lognot (unsafe_get_64 t 0 ));
  unsafe_set_64 u 8  Int64.(lognot (unsafe_get_64 t 8 ));
  unsafe_set_64 u 16 Int64.(lognot (unsafe_get_64 t 16));
  unsafe_set_64 u 24 Int64.(lognot (unsafe_get_64 t 24));
  Printf.printf "after : %a\n%!" pp_hum u;
  u