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Re: [Libcdio-devel] Rock Ridge deep directory support

From: Pete Batard
Subject: Re: [Libcdio-devel] Rock Ridge deep directory support
Date: Sat, 13 Jun 2020 13:36:01 +0100
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0

Hi Thomas,

I'm happy to see you are doing better now. :)

On 2020.06.13 13:16, Thomas Schmitt wrote:
just to show that i began to review the Rock Ridge Deep Directory code,


i wonder why the RR-related code snippet in lib/iso9660/iso9660_fs.c
line 832 is not surrounded by #ifdef HAVE_ROCK and how a freshly calloc'ed
p_stat shall have (p_stat->rr.u_su_fields & ISO_ROCK_SUF_RE) true.

Further i wonder whether the ISO_ROCK_SUF_RE bit can only be set if

Line 819:

   /* Reuse multiextent p_stat if not NULL */
   if (!p_stat) {
     p_stat = calloc(1, stat_len);
     first_extent = true;

how could p_stat->rr.u_su_fields become non-zero ?

Technically we could have a non NULL last_p_stat and with p_stat = last_p_stat the calloc is not guaranteed and p_stat->rr.u_su_fields being zero is not guaranteed...

   } else {
     first_extent = false;
   if (!p_stat) {
     cdio_warn("Couldn't calloc(1, %d)", stat_len);
     return NULL;
   p_stat->type    = (p_iso9660_dir->file_flags & ISO_DIRECTORY)
     ? _STAT_DIR : _STAT_FILE;

why no: #ifdef HAVE_ROCK ?

Because it's redundant. The ISO_ROCK_SUF_RE flag will be set to a non zero only if HAVE_ROCK is enabled (because this is only done in get_rock_ridge_filename() which is guarded), so there's no point in adding the guard where it is not needed, and there is really no performance hit by performing a simple test like this one always.

Line 832:

   /* Ignore Rock Ridge Deep Directory RE entries */

why no: if (_iso9660_is_rock_ridge_enabled(p_image)) ?

Because this is performed in get_rock_ridge_filename() and ISO_ROCK_SUF_RE can only be set if that is the case.

I explicitly designed the code around the idea that the flags we test can only be set if:
- HAVE_ROCK is defined
- _iso9660_is_rock_ridge_enabled() is true
so that we don't have to re-check for the above when checking the flags.



   if (p_stat->rr.u_su_fields & ISO_ROCK_SUF_RE)
     goto fail;

why no: #endif ?

I will continue to read in a few hours.

Have a nice day :)


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