API for excess DOS file attributes??

API for excess DOS file attributes??

[Oleksandr Gavenko]

Under Windows this done through:

   GetFileAttributes()

call. I grep sources and find only 2 occurrence:

./src/fileio.c:1878:      attributes = GetFileAttributes (filename);
./src/w32.c:2630:  else if ((attributes = GetFileAttributes (path)) == -1)

which used for internal purpose...

So I think that I can not excess to this data from Emacs
(native Windows build).

I try rewrite 'follow-cygwin-symlink' from:

   http://www.emacswiki.org/emacs/setup-cygwin.el

for more strict conformance of definition of symbolic link
in Cygwin (from 'cygwin-ug-net-nochunks.html'):

   The file style symlinks are files containing a magic cookie
   followed by the path to which the link points. They are marked
   with the System DOS attribute so that only files with that
   attribute have to be read to determine whether or not the file is
   a symbolic link.

Re: API for excess DOS file attributes??

[Eli Zaretskii]

> From: Oleksandr Gavenko <gavenkoa@gmail.com>
> Date: Thu, 29 Sep 2011 22:59:09 +0300
> 
> So I think that I can not excess to this data from Emacs
> (native Windows build).

Not from Lisp, no.

> I try rewrite 'follow-cygwin-symlink' from:
> 
>    http://www.emacswiki.org/emacs/setup-cygwin.el
> 
> for more strict conformance of definition of symbolic link
> in Cygwin (from 'cygwin-ug-net-nochunks.html'):
> 
>    The file style symlinks are files containing a magic cookie
>    followed by the path to which the link points. They are marked
>    with the System DOS attribute so that only files with that
>    attribute have to be read to determine whether or not the file is
>    a symbolic link.

What's in setup-cygwin.el is about as good as you can get in Lisp.  A
better solution would be to add to file-symlink-p and
make-symbolic-link the ability to recognize and create Cygwin-style
symlink (and Windows 7 style symlink as well), but that requires
changes on the C level.

Re: API for excess DOS file attributes??

[Oleksandr Gavenko]

29.09.2011 23:23, Eli Zaretskii пишет:
>> From: Oleksandr Gavenko<gavenkoa@gmail.com>
>> Date: Thu, 29 Sep 2011 22:59:09 +0300
>>
>> So I think that I can not excess to this data from Emacs
>> (native Windows build).
>
> Not from Lisp, no.
>
>> I try rewrite 'follow-cygwin-symlink' from:
>>
>>     http://www.emacswiki.org/emacs/setup-cygwin.el
>>
>> for more strict conformance of definition of symbolic link
>> in Cygwin (from 'cygwin-ug-net-nochunks.html'):
>>
>>     The file style symlinks are files containing a magic cookie
>>     followed by the path to which the link points. They are marked
>>     with the System DOS attribute so that only files with that
>>     attribute have to be read to determine whether or not the file is
>>     a symbolic link.
>
> What's in setup-cygwin.el is about as good as you can get in Lisp.  A
> better solution would be to add to file-symlink-p and
> make-symbolic-link the ability to recognize and create Cygwin-style
> symlink (and Windows 7 style symlink as well), but that requires
> changes on the C level.
>
OK.

I get next new definition of 'follow-cygwin-symlink', which work with
new (to Cygwin 1.7) style of links:

(when (eq windows-system 'w32)

   (defun follow-cygwin-symlink ()
     "Follow new-style (and also UCS-16) Cygwin symlinks."
     (save-excursion
       (goto-char 0)
       (when (looking-at "!<symlink>\xff\xfe")
         (find-alternate-file
          (substring
           (decode-coding-string
            (buffer-substring (match-end 0) (point-max))
            'utf-16-le)
           0 -1)                           ; -1 for stripping final \0.
          ))))
   (add-hook 'find-file-hooks 'follow-cygwin-symlink)

  )

I don't incorporate it back to emacswiki as don't understand some part
of old code.

Maintainer of this file is Drew Adams, but I don't know how contact
with him.