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  1. PO
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    <p>I suggest defining a simple helper function, <code>make-codec-input-port</code>, that lets you create an input-port from an original input-port and a "codec" function. The key point here -- which wasn't obvious to me from the Racket documentation for <code>make-pipe</code> -- is that you want to run a <code>thread</code> that calls the codec function.</p> <p>Here I show a trivial codec that replaces every <code>#\a</code> character with <code>#\b</code>. You could change its <code>match</code> statement to do something more interesting.</p> <pre><code>#lang racket ;; Given an input-port and a codec function, return a new input-port ;; that is the encoded version. `codec` is (input-port? output-port? ;; -&gt; any). For example can be deflate, inflate, gzip-through-ports, ;; gunzip-through-ports, copy-port (the identity function for this), ;; or your own such function. (define codec-buffer-size (make-parameter 1024)) (define (make-codec-input-port in codec [name #f]) (define-values (pin pout) (make-pipe (codec-buffer-size) name name)) (thread (lambda () (codec in pout) (close-output-port pout))) pin) ;; Example of a codec function. (define (replace-a-with-b in out) ;; (input-port? output-port? -&gt; any) (let loop () (define ch (read-char in)) (unless (eof-object? ch) (write-char (match ch [#\a #\b] [x x]) out) (loop)))) ;; You could also write the codec function a bit more simply using ;; `in-port`: (define (replace-a-with-b in out) ;; (input-port? output-port? -&gt; any) (for ([ch (in-port read-char in)]) (write-char (match ch [#\a #\b] [x x]) out))) ;; Example direct use of the codec function. (let () (define orig-in (open-input-string "axaxax")) (replace-a-with-b orig-in (current-output-port))) ;; =&gt; bxbxbx ;; Example use of the encoded input port. With this, a user of the ;; port need not know anything about the codec function. (let () (define orig-in (open-input-string "axaxax")) (define encoded-in (make-codec-input-port orig-in replace-a-with-b)) (port-&gt;string encoded-in)) ;; =&gt; "bxbxbx" </code></pre>
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    1. POHow to use pipes and custom-ports in Racket
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    1. PTAnswer
    1. USGreg Hendershott
    1. USGreg Hendershott
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    1. CO@JN11 did this help?
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      1. PO
      1. USGreg Hendershott
    2. COI'm looking for something more simple.. But I think I've got if figured out! I'm updating my question now
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      1. PO
      1. USJNevens
 

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