Another ZIP issue -- Does OPC allow use of split/segmented ZIP file?

[caroline arms]

Murata-san,

Here is another issue that probably needs to be run by Microsoft experts.

>From APPNOTE 6.2.0  --
https://www.pkware.com/documents/APPNOTE/APPNOTE-6.2.0.txt

"Large .ZIP files can span multiple diskette media or be split into
user-defined segment sizes."

However, APPNOTE 6.2.0 does not seem to explain how splitting into
user-defined segment sizes is done.

Part 2 Annex B appears to disallow "multi-disk archives" in Table B-1
Part 2 does not seem to mention segments or splitting in the context of ZIP

Part 1 does not seem to say anything about segments in the context of ZIP

I suspect that we should explicitly disallow splitting into user-defined
segment sizes.

Further exploration reveals:

APPNOTE 6.3.3  -- https://www.pkware.com/documents/APPNOTE/APPNOTE-6.3.3.TXT
-- which is what ISO/IEC 21320-1 is based on, does explain the
splitting/segmenting technique, in clause 8.  There is no equivalent text
in APPNOTE 6.2.0

ISO/IEC 21320-1 explicitly disallows both spanning multiple volumes and
splitting into user-defined segments

Also possibly relevant:
>From APPNOTE 6.2.0
"5)  Spanned/Split archives created using PKZIP for Windows
          (V2.50 or greater), PKZIP Command Line (V2.50 or greater),
          or PKZIP Explorer will include a special spanning
          signature as the first 4 bytes of the first segment of
          the archive.  This signature (0x08074b50) will be
          followed immediately by the local header signature for
          the first file in the archive.  A special spanning
          marker may also appear in spanned/split archives if the
          spanning or splitting process starts but only requires
          one segment.  In this case the 0x08074b50 signature
          will be replaced with the temporary spanning marker
          signature of 0x30304b50.  Spanned/split archives
          created with this special signature are compatible with
          all versions of PKZIP from PKWARE.  Split archives can
          only be uncompressed by other versions of PKZIP that
          know how to create a split archive."

Part 2 Annex B does mention    0x08074b50  in B.3

I was thinking that if you were forwarding a question on unknown parts to
Microsoft now, you might send one on this issue too.

      Caroline
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