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TIFF and LibTiff Mail List Archive

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2003.08.07 01:12 "[Tiff] Custom tags", by Ashley Dreier
2003.08.07 06:11 "[Tiff] Custom tags", by Andrey Kiselev
2003.08.07 06:36 "[Tiff] Custom tags", by Ashley Dreier
2003.08.07 16:40 "[Tiff] Custom tags", by Andrey Kiselev
2003.08.07 23:59 "[Tiff] Custom tags", by Ashley Dreier
2003.08.11 05:09 "[Tiff] Custom tags", by Ashley Dreier
2003.08.12 07:48 "[Tiff] Custom tags", by Andrey Kiselev

2003.08.11 05:09 "[Tiff] Custom tags", by Ashley Dreier

Hi Andrey.

Further to my previous posting, I now have the following situation. Writes for non-ascii custom tags of size '1' work fine. If however the size is set to 2 (or higher presumably - i.e. not TIFF_VARIABLE) then I get a corrupted TIFF directory when writing the directory structure. Data from 'purify' indicates that the problem again is in TIFFWriteNormalTag(). The relevant code snippet is:

        case TIFF_LONG:
 case TIFF_SLONG:
                if (wc > 1) {
                   uint32* lp;
                     if (wc == (u_short) TIFF_VARIABLE)
                              TIFFGetField(tif, fip->field_tag, &wc, &lp);
                    else
                            TIFFGetField(tif, fip->field_tag, &lp);
                 if (!WRITEF(TIFFWriteLongArray, lp))
                            return (0);
             } else {
                        if (fip->field_passcount) {
                             uint32* lp;
                             TIFFGetField(tif, fip->field_tag, &wc, &lp);
                            if (!WRITEF(TIFFWriteLongArray, lp))
                                    return 0;
                       } else {
                                /* XXX handle LONG->SHORT conversion */
                         TIFFGetField(tif, fip->field_tag,
                                            &dir->tdir_offset);
                        }
               }
               break;

In my case, 'wc' is set to 2, and fip->field_passcount is also set. I get an 'uninitialised read error' when the WRITEF macro is called, presumably because it's trying to write 2 LONG values out when the reference pointer is addressing the wrong thing. I think the correct code should also look at the 'field_passcount' field as is done in the case where 'wc <= 1'.

Here's my 'diff' output (i.e. cvs diff tif_dirwrite.c) for the LONG custom tag type.

diff -u -w -r1.16 tif_dirwrite.c
--- tif_dirwrite.c      7 Aug 2003 16:39:06 -0000       1.16
+++ tif_dirwrite.c      11 Aug 2003 05:07:35 -0000
@@ -477,6 +477,8 @@
                        uint32* lp;
                        if (wc == (u_short) TIFF_VARIABLE)
                                TIFFGetField(tif, fip->field_tag, &wc, &lp);
+                       else if (fip->field_passcount)
+                               TIFFGetField(tif, fip->field_tag, &wc, &lp);
                        else
                                TIFFGetField(tif, fip->field_tag, &lp);
                        if (!WRITEF(TIFFWriteLongArray, lp))

The case is probably the same for all other custom tag types also.

Regards,

Ashley.

Ashley J. Dreier.                     Email: Ashley.Dreier@csiro.au
CSIRO Manufacturing and Infrastructure Tech, Phone: +61 3 9662 7799
Locked Bag No. 9,                            Fax:   +61 3 9662 7851
Preston, Vic, 3072, Australia.
URL: http://www.msa.cmst.csiro.au/cmst/automation/staff/ajd