Re: How to modify SummaryInformation stream of existing Excel

[Morten Welinder <mortenw gnome org>]

libgsf cannot modify ole2 file members (or zip file members for that
matter) in-place.

The main reason for this is that we have never seriously needed it.
And it is quite a lot of work.

The secondary reason is that doing it is not entirely without problems:
* If not done carefully, old information can be left in unused parts of
   the ole2 file.
* Testing is much more difficult.
* You can end up with fragmented files that require lots of seeking
   to read.

Morten



On Mon, Nov 4, 2013 at 8:13 AM, J.L.Castillo
<jlcastillolorenzo gmail com> wrote:
> Hi all,
>
> I'm trying to modify the SummaryInformation stream of an existing OLE file
> with libgsf. The following code does it right, but deletes all other
> streams:
>
> bool SetStreamGSF(string filepath, string streamName, string & contents)
> {
>     bool success = false;
>     GsfOutput  *output = NULL, *stream = NULL;
>     GsfOutfile *outfile = NULL;
>     GError *err = NULL;
>
>     output = gsf_output_stdio_new (filepath.c_str(), &err);
>     if (output == NULL) {goto SetStreamGSF_end;};
>
>     outfile = gsf_outfile_msole_new (output);
>     if (outfile == NULL) {goto SetStreamGSF_end;};
>
>     stream = gsf_outfile_new_child (outfile, streamName.c_str(), false);
>     if (stream == NULL) {goto SetStreamGSF_end;};
>
>     if(!gsf_output_write (stream, contents.size(), (guint8 *)
> contents.data())) {goto SetStreamGSF_end;};
>
>     success = true;
>
> SetStreamGSF_end:
>
>     if(stream) {gsf_output_close(stream); g_object_unref (G_OBJECT
> (stream)); }
>     if(outfile) {gsf_output_close (GSF_OUTPUT(outfile)); g_object_unref
> (G_OBJECT (outfile));}
>     if(output) {g_object_unref (G_OBJECT (output));}
>     return success;
> }
>
> I checked all sample tests in libgsf, and looked for documentation, but I
> didn't find the proper way to replace a stream in an OLE file without
> deleting other streams. Does anyone know how to do it?
>
> Regards.
> Jose
>
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