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Date: Mon, 21 Mar 2011 12:37:50 +0000
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Subject: Re: cygwin + GetConsoleOutputCP
From: Andy Koppe <andy DOT koppe AT gmail DOT com>
To: cygwin AT cygwin DOT com
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On 21 March 2011 11:17, Corinna Vinschen wrote:
> On Mar 21 07:53, Andy Koppe wrote:
>> On 20 March 2011 19:13, Charles Wilson wrote:
>> > So basically if you specify -iso (or --conv iso) without any of the
>> > "input encoding specification" options like -437 etc, then dos2unix wi=
ll
>> > autodetect attempt to detect the *console* encoding. =C2=A0If it succe=
eds,
>> > then it will "convert" character codes from that encoding to their
>> > equivalent in ISO-8859-1 ("Latin 1") [unconvertible codes are replaced
>> > with an ascii dot]
>> >
>> > Note that this autodetect, if it works, assumes that the console's CP =
is
>> > the input file's CP. =C2=A0Fair enough -- and it's an overridable defa=
ult
>> > anyway. =C2=A0However, I wonder if, in cygwin-1.7, we actually can/sho=
uld use
>> > the "console codepage" in ANY way. =C2=A0Here's the code:
>> >
>> > querycp.c:
>> > #elif defined (WIN32) || defined(__CYGWIN__)
>> >
>> > /* Erwin Waterlander */
>> >
>> > #include <windows.h>
>> > unsigned short query_con_codepage(void) {
>> > =C2=A0 return((unsigned short)GetConsoleOutputCP());
>> > }
>> > #else
>> >
>> > Or if instead, on cygwin, we should use some other mechanism (locale
>> > settings?) to determine the correct default "input" codepage.
>>
>> I think defaulting to the console codepage makes sense for the DOS
>> side of the conversion. Having said that, Windows files that aren't
>> "Unicode", i.e. UTF-16, are usually encoded in the so-called ANSI
>> codepage, e.g. CP1252, so it would make more sense to default to that.
>
> I agree with Andy here. =C2=A0I don't think there are really a lot of fil=
es
> left today, which are encoded using the old DOS codepages.
>
>> However, the real problem with this feature is that the Unix side of
>> the conversion is fixed to ISO-8859-1, which makes it near-useless
>> when Cygwin defaults to UTF-8. And it's no use for non-Western
>> European languages in any case.
>
> Right again. =C2=A0And not only Cygwin, almost all modern UNIX systems are
> using UTF-8 now. =C2=A0The -iso option just doesn't make sense.
>
>> A worthwhile conversion feature would use
>> MultiByteToWideChar()/WideCharToMultiByte() defaulting to the system's
>> ANSI codepage on the DOS side, and mbstowcs()/wcstombs() defaulting to
>
> Well, I'm not sure about that. =C2=A0The complexity of codepage settings =
on a
> Windows system makes the whole afair a guesswork which will always tend
> to do the wrong thing anyway. =C2=A0There are the following codepages ava=
ilable:
>
> - The current input console codepage, GetConsoleCP().
>
> - The current output console codepage, GetConsoleOutputCP().
>
> - The current OEM codepage, GetOEMCP().
>
> - The current ANSI codepage, GetACP().
>
> - The default OEM codepage of the default system locale,
> =C2=A0GetLocaleInfo (LOCALE_SYSTEM_DEFAULT, LOCALE_IDEFAULTCODEPAGE, ...).
>
> - The default ANSI codepage of the default system locale,
> =C2=A0GetLocaleInfo (LOCALE_SYSTEM_DEFAULT, LOCALE_IDEFAULTANSICODEPAGE, =
...).
>
> - The default OEM codepage of the current user or process,
> =C2=A0GetLocaleInfo (LOCALE_USER_DEFAULT, LOCALE_IDEFAULTCODEPAGE, ...).
>
> - The default ANSI codepage of the current user or process,
> =C2=A0GetLocaleInfo (LOCALE_USER_DEFAULT, LOCALE_IDEFAULTANSICODEPAGE, ..=
.).
>
> - The default OEM codepage used for system invariant operations,
> =C2=A0GetLocaleInfo (LOCALE_INVARIANT, LOCALE_IDEFAULTCODEPAGE, ...).
>
> - The default ANSI codepage used for system invariant operations,
> =C2=A0GetLocaleInfo (LOCALE_INVARIANT, LOCALE_IDEFAULTANSICODEPAGE, ...).
>
> Which is the right one?

GetACP(), which "retrieves the current Windows ANSI code page
identifier for the operating system". That's what programs using the
non-Unicode APIs get. It's also the default in Notepad and other
editors.

Other code pages would need to be specified explicitly by the user.


> In theory the option is not useful and should just go away.=C2=A0If you
> have to keep it for backward compatibility, stick to the current
> behaviour and outlaw its use, perhaps be printing a nagging warning
> to stderr.

... and pointing them at iconv (which, to be fair, the -iso
description already does).

Andy

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