(*
 *  Copyright (C) 2000, HELM Team.
 *
 *  This file is part of HELM, an Hypertextual, Electronic
 *  Library of Mathematics, developed at the Computer Science
 *  Department, University of Bologna, Italy.
 *
 *  HELM is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  HELM 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with HELM; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 *  MA  02111-1307, USA.
 *
 *  For details, see the HELM World-Wide-Web page,
 *  http://cs.unibo.it/helm/.
 *)

let debug = true;;
let debug_print s = if debug then prerr_endline s;;

exception Key_already_in of string;;
exception Key_not_found of string;;

class map dbname =
  let perm = 420 in (* permission 644 in decimal notation *)
  let open_dbm () = Dbm.opendbm dbname [ Dbm.Dbm_rdwr; Dbm.Dbm_create ] perm in
  
  object (self)

    inherit ThreadSafe.threadSafe

    val mutable db = open_dbm ()

    initializer Gc.finalise Dbm.close db  (* close db on GC *)

    method add key value =
      self#doWriter (lazy (
        try
          Dbm.add db key value
        with Dbm.Dbm_error "Entry already exists" -> raise (Key_already_in key)
      ))

    method remove key =
      self#doWriter (lazy (
        try
          Dbm.remove db key
        with Dbm.Dbm_error "dbm_delete" -> raise (Key_not_found key)
      ))

    method resolve key =
      self#doReader (lazy (
        try Dbm.find db key with Not_found -> raise (Key_not_found key)
      ))

    method iter (f: string -> string -> unit) =
      self#doReader (lazy (
        Dbm.iter f db
      ))

    method sync =
      self#doWriter (lazy (
        Dbm.close db;
        db <- open_dbm ()
      ))

    method clear =
      self#doWriter (lazy (
        Dbm.close db;
        Sys.remove (dbname ^ ".dir");
        Sys.remove (dbname ^ ".pag");
        db <- open_dbm ()
      ))

  end