[plt-scheme] foreign.ss dll path

I think the Scheme current-directory parameter only changes the
interpreter's view of what the current working directory is.  To
change the working directory of the process and the libraries it
loads, try the chdir function from the C runtime.  For Windows, look
at

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_crt__chdir.2c_._wchdir.asp

For UNIX (POSIX), look at

http://www.umbi.umd.edu/cgi-bin/man-cgi?chdir+2

You'll also want to import the getcwd function.  For Linux, you don't
need to preallocate a buffer, but you do need to specify a maximum
path length:

http://linux.wku.edu/cgi-bin/man2html?getcwd+3

Here's an example:

> (require (lib "foreign.ss"))
> (unsafe!)
> (define rt (ffi-lib #f))
> (define chdir (get-ffi-obj "chdir" rt (_fun _string -> _int)))
> (define getcwd (get-ffi-obj "getcwd" rt (_fun (_pointer = #f) (_int = 1024) -> _string)))
> (getcwd)
"/home/dsilva"
> (chdir "/tmp")
0
> (getcwd)
"/tmp"
> (current-directory)
#<path:/home/dsilva>
> (define (with-c-dir path thunk)
    (define cwd (getcwd))
    (dynamic-wind (lambda () (chdir path))
                  thunk
                  (lambda () (chdir cwd))))
> (with-c-dir "/usr"
     (lambda () (printf "Do some work in ~a~n" (getcwd))))
Do some work in /usr
> (getcwd)
"/tmp"

Daniel

On 10/14/05, Yoav Goldberg <yoav.goldberg at gmail.com> wrote:
> That was fast!
>
> It's working! great!
>
> But the damn dll tries to look for an .ini file ;-(
>
> (oof, this is annoying)
>
>
> On 10/15/05, Eli Barzilay <eli at barzilay.org> wrote:
> > On Oct 15, Yoav Goldberg wrote:
> > > Thanks!
> > >
> > > I used (this-expression-source-directory), and that almost worked -
> > > (ffi-lib ...) finds the dll, but unfortunately, the dll tries to load
> > > *another* dll in the same directory. Do you have any idea how I can
> > > get around that?
> >
> > Load the other dll yourself.  (Define it as some new ffi-lib, even
> > when you don't use it.)
> >
> > --
> >          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
> >                  http://www.barzilay.org/                 Maze is Life!
> >
> >
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