Add mutex.clj

Author: dmiller

src/main/clojure/clojure/core/async/impl/mutex.clj

@@ -0,0 +1,37 @@
+;;   Copyright (c) Rich Hickey and contributors. All rights reserved.
+;;   The use and distribution terms for this software are covered by the
+;;   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
+;;   which can be found in the file epl-v10.html at the root of this distribution.
+;;   By using this software in any fashion, you are agreeing to be bound by
+;;   the terms of this license.
+;;   You must not remove this notice, or any other, from this software.
+
+(ns ^{:skip-wiki true}
+  clojure.core.async.impl.mutex
+  (:import [System.Threading Mutex]))       ;;; [java.util.concurrent.locks Lock ReentrantLock]
+
+;;;(defn mutex []
+;;;  (let [m (ReentrantLock.)]
+;;;    (reify
+;;;     Lock
+;;;     (lock [_] (.lock m))
+;;;     (unlock [_] (.unlock m)))))
+
+
+;; The easiest solution is to define a protocol to give us the same methods (lock, unlock) as java.util.concurrent.locks.Lock, 
+;; then have mutex reify the protocol wrapping a System.Threading.Mutex.
+
+(defprotocol ILock 
+  "Providing the same affordance as java.util.concurrent.locks.Lock"
+   (lock [_] "Lock the lock")
+   (unlock [_] "Unlock the lock"))
+   
+(deftype Lock [^Mutex m] 
+  ILock
+  (lock [x] (.WaitOne m))
+  (unlock [x] (.ReleaseMutex m)))
+  
+  
+(defn mutex []
+  (Lock. (Mutex.)))
+