From 2e8f609597740c63f1a88842edc9df87b0dd6cc9 Mon Sep 17 00:00:00 2001
From: Stefano Zacchiroli <zack@upsilon.cc>
Date: Fri, 24 Feb 2006 00:15:53 +0000
Subject: [PATCH] added a generic (yet rather trivial) module for reference
 counting

---
 components/extlib/.depend        |  2 ++
 components/extlib/Makefile       |  5 ++--
 components/extlib/refCounter.ml  | 49 ++++++++++++++++++++++++++++++++
 components/extlib/refCounter.mli | 31 ++++++++++++++++++++
 4 files changed, 85 insertions(+), 2 deletions(-)
 create mode 100644 components/extlib/refCounter.ml
 create mode 100644 components/extlib/refCounter.mli

diff --git a/components/extlib/.depend b/components/extlib/.depend
index e2c9fc2b8..82a9d39d6 100644
--- a/components/extlib/.depend
+++ b/components/extlib/.depend
@@ -10,3 +10,5 @@ hLog.cmo: hLog.cmi
 hLog.cmx: hLog.cmi 
 trie.cmo: trie.cmi 
 trie.cmx: trie.cmi 
+refCounter.cmo: refCounter.cmi 
+refCounter.cmx: refCounter.cmi 
diff --git a/components/extlib/Makefile b/components/extlib/Makefile
index 4e5c9b5a9..8caad1fca 100644
--- a/components/extlib/Makefile
+++ b/components/extlib/Makefile
@@ -6,8 +6,9 @@ INTERFACE_FILES =		\
         hExtlib.mli		\
 	hMarshal.mli 		\
 	patternMatcher.mli	\
-	hLog.mli \
-	trie.mli \
+	hLog.mli 		\
+	trie.mli 		\
+	refCounter.mli 		\
 	$(NULL)
 IMPLEMENTATION_FILES = \
 	$(INTERFACE_FILES:%.mli=%.ml)
diff --git a/components/extlib/refCounter.ml b/components/extlib/refCounter.ml
new file mode 100644
index 000000000..f5edb69f5
--- /dev/null
+++ b/components/extlib/refCounter.ml
@@ -0,0 +1,49 @@
+(* Copyright (C) 2006, 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://helm.cs.unibo.it/
+ *)
+
+type 'a t = ('a, int ref) Hashtbl.t
+
+let create () = Hashtbl.create 113
+
+let incr ~create_cb counters item =
+  try
+    let counter = Hashtbl.find counters item in
+    incr counter
+  with Not_found ->
+    Hashtbl.add counters item (ref 1);
+    create_cb item
+
+let decr ~delete_cb counters item =
+  try
+    let counter = Hashtbl.find counters item in
+    decr counter;
+    if !counter = 0 then begin
+      Hashtbl.remove counters item;
+      delete_cb item
+    end
+  with Not_found ->
+    prerr_endline "RefCounter: attempt to decrease unexistent counter";
+    assert false
+
diff --git a/components/extlib/refCounter.mli b/components/extlib/refCounter.mli
new file mode 100644
index 000000000..fc5216648
--- /dev/null
+++ b/components/extlib/refCounter.mli
@@ -0,0 +1,31 @@
+(* Copyright (C) 2006, 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://helm.cs.unibo.it/
+ *)
+
+type 'a t
+
+val create: unit -> 'a t
+val incr: create_cb:('a -> unit) -> 'a t -> 'a -> unit
+val decr: delete_cb:('a -> unit) -> 'a t -> 'a -> unit
+
-- 
2.39.2