Ok, so i'm thinking about such one-shot detachable input pipe channels...
(ns async-util.input-pipe
(:require [clojure.core.async.impl.protocols :as impl]
[clojure.core.async :refer [<! close! go-loop]]))
(defprotocol InputPipe
(detach* [p]))
(defn input-pipe
"Creates and return input pipe of supplied channel with attached input
channel."
[ch ch-i]
(let [i (atom ch-i)
p (reify
impl/Channel
(close! [_] (impl/close! ch))
(closed? [_] (impl/closed? ch))
impl/ReadPort
(take! [_ fn1] (impl/take! ch fn1))
impl/WritePort
(put! [_ val fn1] (impl/put! ch val fn1))
InputPipe
(detach* [_] (if (impl/closed? ch)
false
(do (reset! i nil) true))))]
(go-loop [val (<! @i)]
(if-let [i-c @i]
(if (nil? val)
(close! p)
(recur (<! i-c)))
(reset! i nil)))
p))
(defn detach-input
"Detaches input from input-pipe channel, returns false
if input-pipe channel is closed, true otherwise"
[p]
(detach* p))
Dňa piatok, 31. januára 2014 19:18:37 UTC+1 Jan Herich napísal(-a):
>
> Hello Folks,
>
> I need to construct core.async channel with following semantics:
>
> 1. When the channel is created, timeout is attached to channel
> 2. After timeout passes out, channel is closed
> 3. It's possible to detach timeout from the channel before it passes out
>
> Now i implemented it with something like this:
>
> (defn create-cancel-channel
> [channel-to-notify timeout-ms]
> (let [cancel-channel (async/chan)
> timeout-channel (async/timeout timeout-ms)]
> (async/go
> (let [[_ c] (async/alts! [cancel-channel timeout-channel])]
> (when (= c timeout-channel)
> (async/close! cancel-channel)
> (async/close! channel-to-notify))))
> cancel-channel))
>
> ;; transport channel
> (def transport-channel (async/chan))
>
> ;; cancel-channel
> (def cancel-channel (create-cancel-channel transport-channel 2000))
>
> ;; to cancel the transport channel timeout, just close the cancel-channel
> (async/close! cancel-channel)
>
>
> But i'm rather unsatisfied with this solution because it seems little bit
> clunky and what's worse,
> i need to explicitly keep track of those cancel channels.
> Obviously core.async pipe would greatly simplify this, but it seems, that
> there's no way to disconnect
> piped channels. Maybe mult/tap/untap, even if i won't use broadcasting
> semantic of those constructs.
> Any other ideas ?
>
>
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