Subject: Re: bug#22901: drain-input doesn't decode

From: Andy Wingo <[email-masked]>
Date: Mon, 20 Jun 2016 18:12:50 +0200

On Fri 04 Mar 2016 04:09, Zefram <[email-masked]> writes:

> The documentation for drain-input says that it returns a string of
> characters, implying that the result is equivalent to what you'd get
> from calling read-char some number of times.  In fact it differs in a
> significant respect: whereas read-char decodes input octets according to
> the port's selected encoding, drain-input ignores the selected encoding
> and always decodes according to ISO-8859-1 (thus preserving the octet
> values in character form).
>
> $ echo -n $'\1a\2b\3c' | guile-2.0 -c '(set-port-encoding!
> (current-input-port) "UCS-2BE") (write (port-encoding
> (current-input-port))) (newline) (write (map char->integer (let r ((l
> '\''())) (let ((c (read-char (current-input-port)))) (if (eof-object?
> c) (reverse l) (r (cons c l))))))) (newline)'
> "UCS-2BE"
> (353 610 867)
> $ echo -n $'\1a\2b\3c' | guile-2.0 -c '(set-port-encoding!
> (current-input-port) "UCS-2BE") (write (port-encoding
> (current-input-port))) (newline) (peek-char (current-input-port))
> (write (map char->integer (string->list (drain-input
> (current-input-port))))) (newline)'
> "UCS-2BE"
> (1 97 2 98 3 99)

Thanks for the test case!  FWIW, this is fixed in Guile 2.1.3.  I am not
sure what we should do about Guile 2.0.  I guess we should make it do
the documented thing though!

Andy