thread library (actually contains just ThreadSafe module)

diff --git a/helm/ocaml/thread/.cvsignore b/helm/ocaml/thread/.cvsignore
new file mode 100644 (file)
index 0000000..88689d9
--- /dev/null
+++ b/helm/ocaml/thread/.cvsignore
@@ -0,0 +1 @@
+*.cm[iaox] *.cmxa *.[ao]

diff --git a/helm/ocaml/thread/.depend b/helm/ocaml/thread/.depend
new file mode 100644 (file)
index 0000000..8838cb3
--- /dev/null
+++ b/helm/ocaml/thread/.depend
@@ -0,0 +1,2 @@
+threadSafe.cmo: threadSafe.cmi 
+threadSafe.cmx: threadSafe.cmi 

diff --git a/helm/ocaml/thread/Makefile b/helm/ocaml/thread/Makefile
new file mode 100644 (file)
index 0000000..6a5dd3d
--- /dev/null
+++ b/helm/ocaml/thread/Makefile
@@ -0,0 +1,8 @@
+
+PACKAGE = thread
+REQUIRES = threads
+INTERFACE_FILES = threadSafe.mli
+IMPLEMENTATION_FILES = $(INTERFACE_FILES:%.mli=%.ml)
+
+include ../Makefile.common
+

diff --git a/helm/ocaml/thread/threadSafe.ml b/helm/ocaml/thread/threadSafe.ml
new file mode 100644 (file)
index 0000000..4be6618
--- /dev/null
+++ b/helm/ocaml/thread/threadSafe.ml
@@ -0,0 +1,98 @@
+(*
+ * 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/
+ *)
+
+let debug = false
+let debug_print s = if debug then prerr_endline s
+
+class threadSafe =
+  object (self)
+
+    val mutex = Mutex.create ()
+
+      (** condition variable: 'no readers is currently reading' *)
+    val noReaders = Condition.create ()
+
+      (** readers count *)
+    val mutable readersCount = 0
+
+    method private incrReadersCount = (* internal, not exported *)
+      self#doCritical (lazy (
+        readersCount <- readersCount + 1
+      ))
+
+    method private decrReadersCount = (* internal, not exported *)
+      self#doCritical (lazy (
+        if readersCount > 0 then readersCount <- readersCount - 1;
+      ))
+
+    method private signalNoReaders =  (* internal, not exported *)
+      self#doCritical (lazy (
+        if readersCount = 0 then Condition.signal noReaders
+      ))
+
+    method private doCritical: 'a. 'a lazy_t -> 'a =
+      fun action ->
+        debug_print "<doCritical>";
+        (try
+          Mutex.lock mutex;
+          let res = Lazy.force action in
+          Mutex.unlock mutex;
+          debug_print "</doCritical>";
+          res
+        with e ->
+          Mutex.unlock mutex;
+          raise e);
+
+    method private doReader: 'a. 'a lazy_t -> 'a =
+      fun action ->
+        debug_print "<doReader>";
+        let cleanup () =
+          self#decrReadersCount;
+          self#signalNoReaders
+        in
+        self#incrReadersCount;
+        let res = (try Lazy.force action with e -> (cleanup (); raise e)) in
+        cleanup ();
+        debug_print "</doReader>";
+        res
+
+      (* TODO may starve!!!! is what we want or not? *)
+    method private doWriter: 'a. 'a lazy_t -> 'a =
+      fun action ->
+        debug_print "<doWriter>";
+        self#doCritical (lazy (
+          while readersCount > 0 do
+            Condition.wait noReaders mutex
+          done;
+          let res = Lazy.force action in
+          debug_print "</doWriter>";
+          res
+        ))
+
+  end
+

diff --git a/helm/ocaml/thread/threadSafe.mli b/helm/ocaml/thread/threadSafe.mli
new file mode 100644 (file)
index 0000000..0023c89
--- /dev/null
+++ b/helm/ocaml/thread/threadSafe.mli
@@ -0,0 +1,44 @@
+(*
+ * 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 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 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 lazy_t -> 'a
+
+  end
+