[Tickets #4670] unable to open zip files on Mac OS X

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Ticket URL: http://bugs.horde.org/ticket/?id=4670
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 Ticket             | 4670
 Created By         | reitsma at denison.edu
 Summary            | unable to open zip files on Mac OS X
 Queue              | Horde Framework Packages
 Version            | HEAD
 Type               | Bug
 State              | Unconfirmed
 Priority           | 1. Low
 Owners             | 
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reitsma at denison.edu (2006-11-16 03:53) wrote:

The "Download all attachments in zip file" option sometimes results in a
file that cannot be opened by the default zip handler (BOMArchiveHelper)
on Mac OS X. Zipinfo reports the contents of the file properly. The file
can be "repaired" using the following steps:
zipnote file.zip >tmp
zipnote -w file.zip <tmp
In doing this we noted that 12 bytes per file get dropped from the
archive.
The mailing list reports two other zip handlers having problems with IMP
generated zip files: 7-Zip and Stuffit 11.
In Horde/Compress/zip.php I found at line 346:
        /* "Data descriptor" segment (optional but necessary if archive
is
           not served as file). */
        $fr .= pack('V', $crc);
        $fr .= pack('V', $c_len);
        $fr .= pack('V', $unc_len);
This amounts to 12 bytes that gets added for each file in the archive.
These are the 12 bytes that zipnote is stripping out for each file.
PKWare's appnote.txt indicates there is confusion in the use of the data
descriptor segment (should it have a signature, should it only be used in
stream processing, which bit to set if it will be used) and promises a
future appnote to resolve the confusion.

Since we did not want to touch every Macintosh on campus to set it to use
a different default zip handler we went ahead and commented out the data
descriptor segment.