(* Author: Alain Frisch.
   Public domain.
*)

let dummy = Obj.magic (ref 0)

type ('a,'b) t = { keys: 'a array; vals: 'b array; occ: int array }

let create n = { keys = Array.make n (Obj.magic dummy); 
		 vals = Array.make n (Obj.magic dummy);
		 occ = Array.make n 0 }

let get tbl cmp x h v =
  let h = (h land max_int) mod (Array.length tbl.keys) in
  let i = tbl.occ.(h) in
  let k = tbl.keys.(h) in
  if (k != dummy) && (cmp k x) then (tbl.occ.(h) <- succ i; tbl.vals.(h))
  else (
    let r = Lazy.force v in
    if (i = 0) then (tbl.keys.(h) <- x; tbl.vals.(h) <- r; tbl.occ.(h) <- 1)
    else tbl.occ.(h) <- pred i;
    r
  )

let clear tbl =
  let n = Array.length tbl.keys in
  Array.fill tbl.keys 0 n (Obj.magic dummy);
  Array.fill tbl.vals 0 n (Obj.magic dummy);
  Array.fill tbl.occ 0 n 0