gistfile1.clj

;
; STMの挙動を観察する

; スレッドを作るマクロ
; http://code.google.com/p/javaee-study/source/browse/trunk/clojure-concurrency/concurrency.clj?r=5
(import '(java.lang Thread))
(defmacro with-new-thread [& body]
  `(.start (Thread. (fn [] ~@body))))

; 指定された値がTrueになるまでブロックするチェックポイント
(def dict (new java.util.Hashtable))

(defn checkpoint [key]
  (while (not (.get dict key))
    (Thread/sleep 100)))

(defn open [key]
  (.put dict key true)
  (println "open" key))

; STM
(def rx (ref 0))

(with-new-thread
 (dosync
  (println "start transaction 1")
  (checkpoint "11") ; block
  (ref-set rx 1)
  (println "modified ref rx: 1")
  (checkpoint "12") ; block
  (println "finish transaction 1")
  ))

(with-new-thread
 (dosync
  (println "start transaction 2")
  (checkpoint "21") ; block
  (ref-set rx 2)
  (println "modified ref rx: 2")
  (checkpoint "22") ; block
  (println "finish transaction 2")
  ))

(Thread/sleep 500)
(println "----------")
(Thread/sleep 500)

(open "11")

(Thread/sleep 500)
(println "----------")
(Thread/sleep 500)

(open "21")

(Thread/sleep 500)
(println "----------")
(Thread/sleep 500)

(open "12")

(Thread/sleep 500)
(println "----------")
(Thread/sleep 500)

(open "22")

;output----------


$ java -jar clojure-1.4.0.jar stm.clj
start transaction 1
start transaction 2
----------
open 11
modified ref rx: 1
----------
open 21
start transaction 2
start transaction 2
start transaction 2
start transaction 2
----------
start transaction 2
start transaction 2
start transaction 2
start transaction 2
start transaction 2
start transaction 2
open 12
finish transaction 1
start transaction 2
modified ref rx: 2
----------
open 22
finish transaction 2