--- /dev/null
+(*
+ * Copyright (C) 2003-2004:
+ * Stefano Zacchiroli <zack@cs.unibo.it>
+ * for the HELM Team http://helm.cs.unibo.it/
+ *
+ * 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://helm.cs.unibo.it/
+ *)
+
+class threadSafe:
+ object
+
+ (** execute 'action' in mutual exclusion between all other threads *)
+ method private doCritical: 'a. 'a lazy_t -> 'a
+
+ (** execute 'action' acting as a 'reader' i.e.: multiple readers can act
+ at the same time but no writer can act until no readers are acting *)
+ method private doReader: 'a. 'a lazy_t -> 'a
+
+ (** execute 'action' acting as a 'writer' i.e.: when a writer is acting,
+ no readers or writer can act, beware that writers can starve *)
+ method private doWriter: 'a. 'a lazy_t -> 'a
+
+ end
+