MQueryInterpreter: interface updated

[helm.git] / helm / ocaml / mathql_interpreter / mQIConn.ml

diff --git a/helm/ocaml/mathql_interpreter/mQIConn.ml b/helm/ocaml/mathql_interpreter/mQIConn.ml
new file mode 100644 (file)
index 0000000..f38964f
--- /dev/null
+++ b/helm/ocaml/mathql_interpreter/mQIConn.ml
@@ -0,0 +1,93 @@
+(* 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/.
+ *)
+
+exception InvalidConnection
+
+type flag = Postgres | Galax | Stat | Quiet | Warn
+
+type handle = {log : string -> unit;            (* logging function    *)
+               set : flag list;                 (* options             *)
+              pgc : Postgres.connection option (* Postgres connection *)
+             }
+
+let log handle = handle.log
+
+let set handle flag = List.mem flag handle.set
+
+let pgc handle = 
+   match handle.pgc with
+      | None   -> raise InvalidConnection
+      | Some c -> c
+
+let string_of_flag = function
+      | Postgres -> "P"
+      | Galax    -> "G"
+      | Stat     -> "S"
+      | Quiet    -> "Q"
+      | Warn     -> "W"
+
+let flag_of_char = function
+      | 'P' -> [Postgres]
+      | 'G' -> [Galax]
+      | 'S' -> [Stat]
+      | 'Q' -> [Quiet] 
+      | 'W' -> [Warn] 
+      | _   -> []
+
+let string_fold_left f a s =
+   let l = String.length s in
+   let rec aux b i = if i = l then b else aux (f b s.[i]) (succ i) in 
+   aux a 0
+
+let string_of_flags flags =
+   List.fold_left (fun s flag -> s ^ string_of_flag flag) "" flags
+
+let flags_of_string s =
+   string_fold_left (fun l c -> l @ flag_of_char c) [] s
+
+let init myflags mylog =
+   let default_connection_string =
+      "host=mowgli.cs.unibo.it dbname=helm_mowgli_new_schema user=helm"
+   in
+   let connection_string =
+      try Sys.getenv "POSTGRESQL_CONNECTION_STRING"
+      with Not_found -> default_connection_string 
+   in
+   {log = mylog; set = myflags; 
+    pgc = if List.mem Galax myflags 
+       then None else Dbconn.init connection_string
+   }      
+
+let close handle =
+   if set handle Galax then () else Dbconn.close handle.pgc
+
+let connected handle =
+   if set handle Galax then false else
+   try ignore (pgc handle); true with InvalidConnection -> false 
+
+let init_if_connected myflags mylog =
+   let handle = init myflags mylog in
+   ignore (pgc handle); handle
+