Re: iconv or something like that

[Konrad Makowski <poczta@konradmakowski.pl>]

I'm using MySQL. And figure out that if i send query: "SET NAMES utf8" 
or "SET NAMES utf8 COLLATE utf8_general_ci" to the database (in terminal 
for example) mysql converts for me charset of returned data. But if i do 
the same in my guile script it reports error:
In ice-9/boot-9.scm:
  157: 9 [catch #t #<catch-closure 1cff400> ...]
In unknown file:
    ?: 8 [apply-smob/1 #<catch-closure 1cff400>]
In ice-9/boot-9.scm:
   63: 7 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
  432: 6 [eval # #]
  432: 5 [eval # #]
  387: 4 [eval # #]
  387: 3 [eval # #]
  387: 2 [eval # #]
  387: 1 [eval # #]
In unknown file:
    ?: 0 [utf8->string #vu8(80 65 87 69 163)]

ERROR: In procedure utf8->string:
ERROR: Throw to key `decoding-error' with args `("scm_from_stringn" 
"input locale conversion error" 84 #vu8(80 65 87 69 163))'.

My locale say that:
LANG=pl_PL.UTF-8
LANGUAGE=pl:en
LC_CTYPE="pl_PL.UTF-8"
LC_NUMERIC="pl_PL.UTF-8"
LC_TIME="pl_PL.UTF-8"
LC_COLLATE="pl_PL.UTF-8"
LC_MONETARY="pl_PL.UTF-8"
LC_MESSAGES="pl_PL.UTF-8"
LC_PAPER="pl_PL.UTF-8"
LC_NAME="pl_PL.UTF-8"
LC_ADDRESS="pl_PL.UTF-8"
LC_TELEPHONE="pl_PL.UTF-8"
LC_MEASUREMENT="pl_PL.UTF-8"
LC_IDENTIFICATION="pl_PL.UTF-8"
LC_ALL=pl_PL.UTF-8

Any idea?

Konrad

W dniu 23.10.2014 o 20:00, Mark H Weaver pisze:
> Konrad Makowski <poczta@konradmakowski.pl> writes:
>> Is there any solution to convert charset from one encoding to another?
> Yes, but character encodings are only relevant when converting between a
> sequence of _bytes_ (a bytevector), and a sequence of _characters_ [*]
> (a string).  These conversions happen implicitly while performing I/O,
> converting Scheme strings to/from C, etc.
>
> [*] More precisely, Scheme strings are sequences of unicode code points.
>
> It doesn't make sense to talk about the encoding of a Scheme string, or
> to convert a Scheme string from one encoding to another, because they
> are not byte sequences.
>
> It sounds like you already have a Scheme string that was incorrectly
> decoded from bytes, and are asking how to fix it up.  Unfortunately,
> this won't work, because many valid ISO-8859-2 byte sequences are not
> valid UTF-8, and will therefore lead to decoding errors.
>
>> I have database in iso-8859-2 but my script runs in utf-8. I use dbi module.
> Having looked at the guile-dbi source code, I see that it always uses
> the current locale encoding when talking to databases.  Specifically, it
> always uses 'scm_from_locale_string' and 'scm_to_locale_string'.  For
> your purposes, you'd like it to use 'scm_from_stringn' and
> 'scm_to_stringn' instead, with "ISO-8859-2" as the 'encoding' argument.
>
> My knowledge of modern databases is limited, so I'm not sure how this
> problem is normally dealt with.  It seems to me that, ideally, strings
> in databases should be sequences of Unicode code points, rather than
> sequences of bytes.  If that were the case, then this problem wouldn't
> arise.
>
> It would be good if someone with more knowledge of databases would chime
> in here.
>
> In the meantime, I can see a few possible solutions/workarounds:
>
> * Enhance guile-dbi to include an 'encoding' field to its database
>    handles, add a new API procedure to set it, and use it in all the
>    appropriate places.  This only makes sense if database strings are
>    conceptually byte sequences, otherwise it should probably be fixed in
>    some other way.
>
> * Hack your local copy of guile-dbi to use 'scm_from_stringn' and
>    'scm_to_stringn' with a hard-coded "ISO-8859-2" in the appropriate
>    places.
>
> * Use 'setlocale' to set a ISO-8859-2 locale temporarily while
>    performing database queries.
>
> Which database are you using?
>
>       Mark
>