windows trial: Replacement of link(2)?

[Derek Atkins]

My personal feeling is that you could just try a creat(O_EXCL) on
the lockfile and use the results.  I think window's createfile
is "atomic enough" for us to know whether the datafile is
being used.

Granted, what you need to do is:

    create lockfile
    open datafile

-derek

Christian Stimming <stimming at tuhh.de> writes:

> Hi,
>
> Windows/mingw32 doesn't have link(2) and I think this is because vfat et
> al don't support hard links anyway. We use this function only in one
> file, src/backend/file/gnc-backend-file.c. I'd need some input as for
> how to replace that function. My own proposed patch is attached. Please
> comment whether this seems fine or not.
>
> The file locking on windows can be a bit less strict than on Unix
> because on Windows, the OS will not allow different processes to open
> the same file for editing anyway.
>
> Christian
> Index: src/backend/file/gnc-backend-file.c
> ===================================================================
> --- src/backend/file/gnc-backend-file.c	(revision 13630)
> +++ src/backend/file/gnc-backend-file.c	(working copy)
> @@ -123,17 +123,31 @@
>  
>      strcpy (pathbuf, be->lockfile);
>      path = strrchr (pathbuf, '.');
> -    sprintf (path, ".%lx.%d.LNK", gethostid(), getpid());
> +    sprintf (path, ".%lx.%d.LNK", 
> +#ifdef HAVE_GETHOSTID
> +	     gethostid(),
> +#else
> +	     0,
> +#endif
> +	     getpid());
>  
> -    rc = link (be->lockfile, pathbuf);
> +    rc = 
> +#ifdef HAVE_LINK
> +      link (be->lockfile, pathbuf)
> +#else
> +      -1
> +#endif
> +      ;
>      if (rc)
>      {
> +#ifdef HAVE_LINK
>          /* If hard links aren't supported, just allow the lock. */
>          if (errno == EPERM
> -#ifdef EOPNOTSUPP
> +# ifdef EOPNOTSUPP
>  	    || errno == EOPNOTSUPP
> +# endif
> +	    )
>  #endif
> -	    )
>          {
>              be->linkfile = NULL;
>              return TRUE;
> @@ -337,14 +351,22 @@
>  static gboolean
>  gnc_int_link_or_make_backup(FileBackend *be, const char *orig, const char *bkup)
>  {
> -    int err_ret = link(orig, bkup);
> +    int err_ret = 
> +#ifdef HAVE_LINK
> +      link (orig, bkup)
> +#else
> +      -1
> +#endif
> +      ;
>      if(err_ret != 0)
>      {
> +#ifdef HAVE_LINK
>          if(errno == EPERM
> -#ifdef EOPNOTSUPP
> +# ifdef EOPNOTSUPP
>  	   || errno == EOPNOTSUPP
> +# endif
> +	   )
>  #endif
> -	   )
>          {
>              err_ret = copy_file(orig, bkup);
>          }
> _______________________________________________
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> gnucash-devel at gnucash.org
> https://lists.gnucash.org/mailman/listinfo/gnucash-devel

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available