[flexi-streams-devel] in-memory streams have no way to set external-format?

[Andreas Fuchs]

Hi all,

I would like to teach cl-irc about the goodness of external-formats,
and because irc doesn't let users specify which external format to
use, I need something as flexible as flexi-streams (-:

So, once I've read an irc command (as a "line" of latin-1 characters),
I'd like to convert it to text that looks the least insane, which is
why my code tries several external-formats in a row and returns as
soon as it found one that doesn't throw an error:

(defun try-decode-line (line external-formats)
  (loop for external-format in external-formats
        for decoded = nil
        for error = nil
        do (multiple-value-setq (decoded error)
               (ignore-errors
                 (flexi-streams:with-input-from-sequence (in line)
                   (setf (flexi-streams:flexi-stream-external-format in)
                         external-format)
                   (read-line in))))
        do (format t "~&tried ~s: ~S~% error: ~A~%" external-format decoded
                   error)
        if decoded
          do (return decoded)))

Try it with:

(try-decode-line "foo" '((:UTF-8 :EOL-STYLE :LF)
                         (:LATIN-1 :EOL-STYLE :LF)))

(alternatively, (map 'vector #'char-code "foo") and with (list
(make-external-format...)) calls) And for each of the external
formats, I get:

There is no applicable method for the generic function
  #<STANDARD-GENERIC-FUNCTION (SETF FLEXI-STREAMS:FLEXI-STREAM-EXTERNAL-FORMAT) (2)>
when called with arguments
  ((:UTF-8 :EOL-STYLE :LF)
    #<FLEXI-STREAMS::VECTOR-INPUT-STREAM {ABEFA91}>).

Hrmpf! Am I abusing flexi-streams too much or is that a bug? How
should one read externally-formatted data from an in-memory stream,
anyway?

And are string-backed in-memory streams even allowed? How to specify
the internal external format for them? (-:

Thanks for your time and for developing flexi-streams. In return, I
hope to be able to buy you a beverage of your choice in Hamburg (-:

Cheers,
-- 
Andreas Fuchs, (http://|im:asf@|mailto:asf@)boinkor.net, antifuchs