Unix VM path encodings

 
Hi -

Due to a bug reported against Qwaq Forums I needed to look into how the
Unix VM encodes file and path names and got terribly confused. My test
case was to create a file with an Umlaut("Jürgen") and to see what both
Squeak and the Unix shell reports with varying settings of -pathenc and
-textenc.

I started with the assumption that since the file system I was running
this on is UTF-8 the default settings (-textenc MacRoman and -pathenc
UTF-8) ought to be correct. However, the result was very surprising. The
file name was reported incorrectly both in the file list as well as by
the OS - the file list reported "J?" (truncated after the question mark)
and the Unix shell reported "J?rgen" but with a "funky ?" (the glyph is
hard to describe without a screenshot; it was neither an umlaut nor a
regular question mark).

Playing with the settings I could not find any combination that resulted
in a consistent representation for all the different views - either the
Unix shell was off or Squeak's view was off no matter how I set those
encodings. Can someone explain to me how I need to set these values to
get a consistent view on file names both from Squeak and Unix?

Cheers,
   - Andreas

For Sophie we spend hours/days? getting this correct. However we  
really didn't check out the pure Unix variation.

Actually let's some other utf-32 character versus ü

Oh let's say LATIN CAPITAL LETTER SCHWA   -> UTF-8  0xC68F UTF-32  
0x0000018F

Ə

in the os-x 10.5.1 Finder we see

Ə.png

and in a terminal session we see

-rw-r--r--   1 johnmci  staff  26451 Apr 10  2007 Ə.png

in both cases just in case you can't see this in the email the  
character is visually correct.

Using Squeak 3.10Alpha 7092 with a Mac Carbon VM 3.8.18b1 set to utf8
when we use the file list morphic What we see is
?.png
the ? is 0x3F

of course it says it can't open the file, because the smalltalk code  
(which code is an exercise for the reader) has mangled the 0xC68F into  
0x3F. In asking about this a few years back I think I was told it  
converts the VM data to latin1. However the conversion from macroman  
to latin1 and back *usually* is workable, mind only if the characters  
are <= 0xFF

However utf8 to latin1 usually ends up broken which is why the mac  
carbon VM is set to macroman by default.

Recall that in os-x HFS Plus converts all file names to decomposed  
Unicode, while Macintosh keyboards generally produce precomposed  
Unicode.  The macintosh carbon VM converts back and forth between the  
pre-composed to decomposed unicode when it is using UTF8 encoding.  
This also depends on the file system and what it thinks it wants to  
store unicode characters as...

Now in Sophie when we import this into Sophie the URI that was  
generated is

/Users/johnmci/Work%20In%20Progress/squeak%20Bugs/%C6%8F.png

that becomes

'/Users/johnmci/Work In Progress/squeak Bugs/Æ∑.png'

But the VM ensures the proper thing is done. In sophie we store all  
media paths as encoded URI objects, and convert to
what is required when we need to access the media.

Oh and btw if you enter
file:///Users/johnmci/Work%20In%20Progress/squeak%20Bugs/%C6%8F.png
into FireFox, it's happy too.  Oddly when you enter it into Safari it  
becomes file:///Users/johnmci/Work%20In%20Progress/squeak%20Bugs/Ə.png

Oh and if I take the Ə.png from a terminal session, or the finder  
window
and paste into a Sophie text field, yes it's Ə.png
because the extended clipboard support converts it properly from utf8,
Mind in TextEdit it comes across as RTF which is a different issue,  
but *still* is correctly converted into utf-32 in Sophie.

People of course are welcome to uncover unicode character issue with  
Sophie and how it deals with file names or
textual data in text fields.

On Dec 29, 2007, at 11:32 PM, Andreas Raab wrote:

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On Dec 29, 2007, at 11:32 PM, Andreas Raab wrote:

> Hi -
>
> Due to a bug reported against Qwaq Forums I needed to look into how  
> the Unix VM encodes file and path names and got terribly confused.

Also see

        From: [hidden email]
        Subject: Re: mac carbon VM goes to unix file names, testers needed

        Date: February 6, 2006 12:54:17 AM PST (CA)

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Oh, interesting. That reminds me of the fix that I needed for Windows,
let me see... yes, here it is: LanguageEnvironment
class>>defaultFileNameConverter needs to be fixed since it is (wrongly)
guessing the file name encoding based on the currently active locale
(which makes no sense btw, since the locale doesn't mean Jack for file
name encodings). Hm ... lemme try this ... ah, interesting. It appears
that I can make the Umlauts work on Unix correctly if and only if:
* I fix the above method to return UTF8TextConverter in every case [*1]
* I use -pathenc MacRoman -textenc MacRoman
Which makes no sense to me since neither the path nor the text encoding
is MacRoman but it appears to work. Huh?

[*1] And that of course reminds me that nobody has really made any
comment on why the hell we still deal with all of these nonsensical
legacy encodings and don't just go straight to UTF-8 in the VM interface
which would simplify *lots* of cruft in the code.

Cheers,
   - Andreas

John M McIntosh wrote:

 
El dom, 30-12-2007 a las 10:28 +0100, Andreas Raab escribió: And what's the result of dragging and dropping a file (a gif, mp3, or
any other with the mime type registered) over the image if the file name
contains the Umlauts?
That has never worked either in the unix vm...



> [*1] And that of course reminds me that nobody has really made any
> comment on why the hell we still deal with all of these nonsensical
> legacy encodings and don't just go straight to UTF-8 in the VM interface
> which would simplify *lots* of cruft in the code.

Totally agree, maybe every vm hacker thinks everybody use english or it
was just too messy to waste time on it...

On Dec 30, 2007, at 1:28 AM, Andreas Raab wrote:


Careful now is that

ü
0x9F in macroman  or
0x000000FC   in utf-32

which is coming back from the VM, then what does the  
LanguageEnvironment class>>defaultFileNameConverter do
and which FONT and character set does that font think it lives in?  
Since the hex value might not have proper representation if you use a  
non-unicode proper font after converting from something to unicode....


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John M. McIntosh <[hidden email]>
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On Dec 30, 2007, at 1:28 AM, Andreas Raab wrote:

> [*1] And that of course reminds me that nobody has really made any  
> comment on why the hell we still deal with all of these nonsensical  
> legacy encodings and don't just go straight to UTF-8 in the VM  
> interface which would simplify *lots* of cruft in the code.

I think all the vertical squeak packages (scratch, sophie, plopp) use  
UTF8 and get to ignore the file tools. And
don't get Tim started on what he thinks of the classes that deal with  
files...

Personally I wanted to move the carbon vm to utf8 awhile back, but  
well as you see all the morphic file tools would
break in interesting ways.
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John M. McIntosh <[hidden email]>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
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> Hm ... lemme try this ... ah, interesting. It appears
> that I can make the Umlauts work on Unix correctly if and only if:
> * I fix the above method to return UTF8TextConverter in every case [*1]
> * I use -pathenc MacRoman -textenc MacRoman
> Which makes no sense to me since neither the path nor the text encoding
> is MacRoman but it appears to work. Huh?

  Yes, on Unix VM, another historical mishappen caused it; "MacRoman"
still means "no conversion" so that if the image passes UTF-8 string,
the UTF-8 string is passed to system calls.

> [*1] And that of course reminds me that nobody has really made any
> comment on why the hell we still deal with all of these nonsensical
> legacy encodings and don't just go straight to UTF-8 in the VM interface
> which would simplify *lots* of cruft in the code.

  Well, nobody tried to change stuff on the all platforms at once.
Windows is doing ok with 3.10 VM and OLPC Etoys image (there is still
code that deals with older VM... typical installation for people is to
install stuff from squeakland.org and then use Etoys image).

-- Yoshiki

 

On Dec 30, 2007, at 2:11 AM, Yoshiki Ohshima wrote:

Er, well I'm not sure that's quite accurate? In looking at  
sqUnixCharConv.c  it seems to say that if the
text encoding is macroman and the path encoding is macroman the
translation from unix path to squeak would be macroman to macroman so  
nothing would happen.

Convert(sq,ux, Path, sqTextEncoding, uxPathEncoding, 1, 0); //  
normalised paths for HFS+
Convert(ux,sq, Path, uxPathEncoding, sqTextEncoding, 0, 0);

in
sqInt dir_Lookup(char *pathString, sqInt pathStringLength, sqInt index,
/* outputs: */  char *name, sqInt *nameLength, sqInt *creationDate,  
sqInt *modificationDate,
                sqInt *isDirectory, squeakFileOffsetType *sizeIfFile)

we find
  *nameLength= ux2sqPath(dirEntry->d_name, nameLen, name, MAXPATHLEN,  
0);


However I note the carbon vm does
   if (norm) // HFS+ imposes Unicode2.1 decomposed UTF-8 encoding on  
all path elements
     CFStringNormalize(str, kCFStringNormalizationFormD); // canonical  
decomposition
   else
     CFStringNormalize(str, kCFStringNormalizationFormC); // pre-
combined

but the unix VM does not do this, which I think is an error based on:

See
        From: [hidden email]
        Subject: [Vm-dev] Patch for filename normalization of mac vm

        Date: March 11, 2007 8:21:06 PM PDT (CA)

        To: [hidden email]




PS I note if you feed CFStringCreateWithBytes  bad data, why it  
returns NULL, then the lurking CFStringCreateMutableCopy core dumps  
the VM.  That's why I check for it in the carbon vm. Normally you  
won't see
this issue unless you get creative...
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John M. McIntosh <[hidden email]>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
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Yoshiki Ohshima wrote:
Playing around a little it appears as if the Unix VM always converts
path names with the assumption that Squeak uses MacRoman in the image
and only -pathenc affects the translation between file system and the
image (i.e., -textenc has *no* effect on path name translation
whatsoever). Can someone confirm this? It would explain why -pathenc
MacRoman works (since like you say it's really the "no conversion" flag)
if combined with a proper file name converter in the image.

>> [*1] And that of course reminds me that nobody has really made any
>> comment on why the hell we still deal with all of these nonsensical
>> legacy encodings and don't just go straight to UTF-8 in the VM interface
>> which would simplify *lots* of cruft in the code.
>
> Well, nobody tried to change stuff on the all platforms at once.
> Windows is doing ok with 3.10 VM and OLPC Etoys image (there is still
> code that deals with older VM... typical installation for people is to
> install stuff from squeakland.org and then use Etoys image).

What encoding options are being used on OLPC? Do non-ascii file names,
clipboard, drag and drop etc. work on OLPC?

Cheers,
   - Andreas

On Dec 30, 2007, at 4:09 AM, Andreas Raab wrote:

Mmm for the -pathenc and the -textenc from what I can see the data  
coming from the file system  is said to exist
in the form -pathenc and translated to a CFString in UTF-32, then  
translated back to a byte string in -textenc.

In sending the data to the file system, it said it exists in the form -
textenc, then translated to a CFString in UTF-32
then     CFStringNormalize(str, kCFStringNormalizationFormD); //  
canonical decomposition, then translated back to
a byte string in -pathenc.

I'll note the kCFStringNormalizationFormD operation (and all above/
below) only occurs if this is macintosh. If this is a Linux/BSD unix  
system then iconv is used.  So is this on a mac or some Linux/BSD  
system?

That and I think a kCFStringNormalizationFormC is needed in the first  
step to properly compose the characters.

For background

Ok, let's see in the mac carbon vm we get back from the file system  for
LATIN CAPITAL LETTER SCHWA + LATIN CAPITAL LETTER A WITH ACUTE
ƏÁ.png

0xC6, 0x8F, A, 0xCC, 0x81, .png   Note how the A0xCC81 is the  
decomposed UTF8, this is what is stored in the HFS+ file system.

We convert that from UTF8 to the target of MacRoman for path names by  
default in the base carbon VM.
This means converting to a CFString from kCFStringEncodingUTF8
then applying
CFStringNormalize(str, kCFStringNormalizationFormC); // pre-combined
then pulling back the bytes as MacRoman, that becomes

?, 0xE7, .png

since the translation of the Ə  from utf8 to macroman fails,  but the  
E7 is correct macroman for the Á

Now if I set the vm up to use UTF8 as the path name default.

after we apply the kCFStringNormalizationFormC step and pull back the  
data as UTF8 it is

0xC6, 0x8F, 0xC3, 0x81, .png   where the 0xC381 is the  (LATIN CAPITAL  
LETTER A WITH ACUTE) in UTF8 or 0x00c1 in utf-16 or 0x000000c1 in utf-32

Now if I remove the CFStringNormalize(str,  
kCFStringNormalizationFormC); // pre-combined
which does not exist in the base unix vm, then I get back

0xC6, 0x8F, A, 0xCC, 0x81,  '.png'

which is the decomposed UTF8.   I'll note in the file browser it shows  
as
Æ∑AÌ∞.png

but it does work....

NOW the question is what does the translation do...  mmm Well if I try
LanguageEnvironment classPool at: #FileNameConverterClass put:  
UTF8TextConverter
then it shows:
?A?.png

which is mmm, less wrong? But it does work.

Now if in the base unix VM you take  path encoding and text encoding  
and set to macroman
Convert(ux,sq, Path, uxPathEncoding, sqTextEncoding, 0, 0);
then we are saying the operating system (unix) path encoding is  
macroman and the squeak path name encoding is macroman that gives back

0xC6, 0x8F, A, 0xCC, 0x81, '.png'

since as thought the macroman to macroman translation does nothing.

However the UTF8TextConverter does not work with decomposed UTF8 so  
what the user would see is not correct, since it assumes we are  
working with precomposed UTF8 when it converts it to UTF-32 for the  
font system's enjoyment.


I suspect to fix properly a
CFStringNormalize(str, kCFStringNormalizationFormC);
is needed in the Unix sqUnixCharConv.c and applied when applicable.


Notes from Apple's site

For example, an Á (A acute) can be encoded either precomposed, as U
+00C1 (LATIN CAPITAL LETTER A WITH ACUTE), or decomposed, as U+0041 U
+0301 (UTF8 is 0xCC81)  (LATIN CAPITAL LETTER A followed by a  
COMBINING ACUTE ACCENT). Precomposed characters are more common in the  
Windows world, whereas decomposed characters are more common on the Mac.



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John M. McIntosh <[hidden email]>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
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  Andreas,

> Playing around a little it appears as if the Unix VM always converts
> path names with the assumption that Squeak uses MacRoman in the image
> and only -pathenc affects the translation between file system and the
> image (i.e., -textenc has *no* effect on path name translation
> whatsoever). Can someone confirm this? It would explain why -pathenc
> MacRoman works (since like you say it's really the "no conversion" flag)
> if combined with a proper file name converter in the image.

  I think it is.  If I remember correctly, this was introduced before
3.8 (around 3.7 era, I believe) by Ned, and that was only to make
something he was trying to do work.

> > Well, nobody tried to change stuff on the all platforms at once.
> > Windows is doing ok with 3.10 VM and OLPC Etoys image (there is still
> > code that deals with older VM... typical installation for people is to
> > install stuff from squeakland.org and then use Etoys image).
>
> What encoding options are being used on OLPC? Do non-ascii file names,
> clipboard, drag and drop etc. work on OLPC?

  Filenames are in UTF-8.  Clipboard and Drag and drop uses somewhat
strange mechanism, but they are normalized to UTF-8 as well.

-- Yoshiki

 
Yoshiki Ohshima wrote:
>> What encoding options are being used on OLPC? Do non-ascii file names,
>> clipboard, drag and drop etc. work on OLPC?
>
>   Filenames are in UTF-8.  Clipboard and Drag and drop uses somewhat
> strange mechanism, but they are normalized to UTF-8 as well.

Odd. Checking the latest OLPC image I have access to (etoys2.3-1867)
there is nothing I can see that would deal properly in the image with
non-ascii file names on Unix. LanguageEnvironment still returns "self
currentPlatform class fileNameConverterClass" which won't use an UTF-8
converter anywhere. So unless I'm missing something it probably
shouldn't work on OLPC. Maybe try it with some "real" UTF-32 names?

Cheers,
   - Andreas

 
  Andreas,

> Odd. Checking the latest OLPC image I have access to (etoys2.3-1867)
> there is nothing I can see that would deal properly in the image with
> non-ascii file names on Unix. LanguageEnvironment still returns "self
> currentPlatform class fileNameConverterClass" which won't use an UTF-8
> converter anywhere. So unless I'm missing something it probably
> shouldn't work on OLPC. Maybe try it with some "real" UTF-32 names?

  Ah, you are right.  the code wasn't the way I remember it should be.
Latin1Environment (which should be called WesternEuropeanEnvironment)
flieNameConverterClass should be a bit more elaborated (or just
returning UTF8TextConverter).

-- Yoshiki