(defn coll->enumeration [coll] (clojure.lang.SeqEnumeration. coll)) On Friday, July 13, 2012 7:13:54 AM UTC-7, Meikel Brandmeyer (kotarak) wrote: > > Hi, > > I think you don't handle the switching of streams correctly. You have to > keep track with atoms. But then you run into thread-safety issues. > > (defn concat-input-stream > "Gets one or many input streams and returns a new input stream that > concatenates the given streams." > [is & streams] > (let [is (atom is) > streams (atom streams) > switch! (fn [] > (locking is > (.close @is) > (reset! is (first streams)) > (swap! streams rest))) > do-read (fn > ([is] (if is (.read is) -1)) > ([is arr] (if is (.read is arr) -1)) > ([is arr off len] (if is (.read is arr off len) -1)))] > (proxy [java.io.InputStream] [] > (close > [] > (when @is > (.close @is) > (doseq [s @streams] (.close s)))) > (read > ([] > (let [ch (do-read @is)] > (if (neg? ch) > (do > (switch!) > (if @is > (.read this) > -1)) > ch))) > ([arr] > (let [n (do-read @is arr)] > (if (neg? n) > (do > (switch!) > (if @is > (.read this arr) > -1)) > n))) > ([arr off len] > (let [n (do-read @is arr off len)] > (if (neg? n) > (do > (switch!) > (if @is > (.read this arr off len) > -1)) > n))))))) > > You could also use java.io.SequenceInputStream with a small helper. > > (defn coll->enumeration > [coll] > (let [s (atom coll)] > (reify [java.util.Enumeration] [] > (hasMoreElements [this] > (boolean (swap! s seq))) > (nextElement [this] > (locking this > (if-let [sq (seq @s)] > (let [e (first sq)] > (reset! s (rest sq)) > e) > (throw (java.util.NoSuchElementException.)))))))) > > (defn concat-input-stream > "Gets one or many input streams and returns a new input stream that > concatenates the given streams." > [is & streams] > (java.io.SequenceInputStream. (coll->enumeration (cons is streams)))) > > All code untested. > > Kind regards > Meikel > >
-- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
