ASYNC-257 Make channels Datafiable

Author: puredanger

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

@@ -92,7 +92,8 @@ to catch and handle."
   buffer must be specified. ex-handler must be a fn of one argument -
   if an exception occurs during transformation it will be called with
   the Throwable as an argument, and any non-nil return value will be
-  placed in the channel."
+  placed in the channel. Channels implement Datafiable; use datafy
+  to obtain the state of the channel and its buffer."
   ([] (chan nil))
   ([buf-or-n] (chan buf-or-n nil))
   ([buf-or-n xform] (chan buf-or-n xform nil))

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

@@ -303,3 +303,15 @@
                (add! buf val)
                (catch Throwable t
                  (handle buf exh t)))))))))
+
+(extend-protocol clojure.core.protocols/Datafiable
+  ManyToManyChannel
+  (datafy [c]
+    (let [b (.buf c)]
+      {:buffer-type (if b
+                      (-> b class .getSimpleName symbol)
+                      :none)
+       :buffer-count (count b)
+       :put-count (count (.puts c))
+       :take-count (count (.takes c))
+       :closed? (impl/closed? c)})))