On Mon, Feb 7, 2011 at 8:09 PM, Andreas Kostler
<[email protected]> wrote:
> Hi all,
> Is it possible to read from a lazy input sequence? I have a telnet
> connection using commons.telnet and I want to do something like:
> (def telnet (TelnetClient.))
> (def in (. telnet getInputStream))
>
> ; How do I do this?
> (def read-until
> ; read from a lazy input sequence UNTIL prompt is matched and return
> what's been read
> [prompt input-stream]
> ...)
>
> Every idea is appreciated :)
Lazy seq of characters from input sequence:
(defn lazy-input
"Returns a lazy sequence of characters from an input stream or Reader."
[input-stream]
(let [step (fn step []
(let [c (.read input-stream)]
(when-not (== c -1)
(cons (char c) (lazy-seq (step))))))]
(lazy-seq (step))))
Read up until a subseq:
(defn take-until-subseq
"Searches forward through s until subseq or end of s.
Returns s from start to just before first occurrence of subseq."
[s subseq]
(let [l (count subseq) ss (partition l 1 s) subseq (seq subseq)]
(map first (take-while (fn [[_ x]] (not= x subseq)) (map vector s ss)))))
Read until a prompt from an input stream:
(defn read-until
"Reads from an input stream or Reader until prompt."
[prompt input-stream]
(apply str (take-until-subseq (lazy-input input-stream) prompt)))
Test it:
user=> (read-until "baz" (java.io.StringReader. "foobarbazquux"))
"foobar"
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