(*
 * Size: computes the memory size of an ocaml value.
 * Copyright (C) 2000 Jean-Christophe FILLIATRE
 * 
 * This software is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License version 2, as published by the Free Software Foundation.
 * 
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * 
 * See the GNU Library General Public License version 2 for more details
 * (enclosed in the file LGPL).
 *)

(*i $Id: size.ml,v 1.5 2001/02/07 09:22:00 filliatr Exp $ i*)

(*i*)
open Obj
(*i*)

(*s Pointers already visited are stored in a hash-table, where
    comparisons are done using physical equality. *)

module H = Hashtbl.Make(
  struct 
    type t = Obj.t 
    let equal = (==) 
    let hash o = Hashtbl.hash (magic o : int)
  end)
	     
let node_table = (H.create 257 : unit H.t)

let in_table o = try H.find node_table o; true with Not_found -> false

let add_in_table o = H.add node_table o ()

let reset_table () = H.clear node_table

(*s Objects are traversed recursively, as soon as their tags are less than
    [no_scan_tag]. [count] records the numbers of words already visited. *)

let size_of_double = size (repr 1.0)

let count = ref 0

let rec traverse t =
  if not (in_table t) then begin
    add_in_table t;
    if is_block t then begin
      let n = size t in
      let tag = tag t in
      if tag < no_scan_tag then begin
	count := !count + 1 + n;
	for i = 0 to n - 1 do
      	  let f = field t i in 
	  if is_block f then traverse f
	done
      end else if tag = string_tag then
	count := !count + 1 + n 
      else if tag = double_tag then
	count := !count + size_of_double
      else if tag = double_array_tag then
	count := !count + 1 + size_of_double * n 
      else
	incr count
    end
  end

(*s Sizes of objects in words and in bytes. The size in bytes is computed
    system-independently according to [Sys.word_size]. *)

let size_w o =
  reset_table ();
  count := 0;
  traverse (repr o);
  !count

let size_b o = (size_w o) * (Sys.word_size / 8)

let size_kb o = (size_w o) / (8192 / Sys.word_size)