(***********************************************************************)
(*                                                                     *)
(*                           Objective Caml                            *)
(*                                                                     *)
(*          Francois Rouaix, projet Cristal, INRIA Rocquencourt        *)
(*                                                                     *)
(*  Copyright 1996 Institut National de Recherche en Informatique et   *)
(*  Automatique.  Distributed only by permission.                      *)
(*                                                                     *)
(***********************************************************************)

(* $Id *)

(* Module [Db]: interface to the DB databases *)

(* this collides with Unix *)
type open_flag =
    O_CREAT
  | O_EXCL
  | O_RDONLY
  | O_RDWR
  | O_TRUNC

type routine_flag =
    R_CURSOR
  | R_FIRST
  | R_LAST
  | R_NEXT
  | R_NOOVERWRITE
  | R_PREV
  | R_SETCURSOR


(* All other fields have default values *)
type btree_flag =
    Duplicates        (* means R_DUP *)
  | Cachesize of int


type file_perm = int

exception DB_error of string
  (* Raised by the following functions when an error is encountered. *)

external caml_db_init : unit -> unit
    = "caml_db_init"

let _ = Callback.register_exception "dberror" (DB_error "")
let _ = caml_db_init()

type key = string
type data = string
type t

(* Raw access *)
external dbopen : string -> open_flag list -> file_perm -> btree_flag list -> t
    = "caml_db_open"
    (* [dbopen file flags mode dupentries] *)

(* The common subset of available primitives *)
external close : t -> unit
    = "caml_db_close"

external del : t -> key -> routine_flag list -> unit
    = "caml_db_del"
    (* raise Not_found if the key was not in the file *)

external get : t -> key -> routine_flag list -> data
    = "caml_db_get"
    (* raise Not_found if the key was not in the file *)

external put : t -> key -> data -> routine_flag list -> unit
    = "caml_db_put"

external seq : t -> key -> routine_flag list -> (key * data)
    = "caml_db_seq"

external sync : t -> unit
    = "caml_db_sync"


(* Wrap-up as for other table-like types *)
let add db x v = put db x v [R_NOOVERWRITE]
let find db x = get db x []
let find_all db x = 
  try
    match seq db x [R_CURSOR] with
      k, v when k = x ->
	let l = ref [v] in
	begin
	  try 
	    while true do
	      let k, v = seq db x [R_NEXT] in
	      if k = x then l := v :: !l
	      else raise Exit
	    done;
	    !l
	  with
	    Exit | Not_found -> !l
	end
    | _ -> (* its greater than x *) []
  with
    Not_found -> []

let remove db x = del db x []

let iter f db = 
  let rec walk k =
    let k, v = seq db k [R_NEXT] in
    f k v;
    walk k
  in
  try
    let k, v = seq db "" [R_FIRST] in
    f k v;
    walk k
  with
    Not_found -> ()