[Libguestfs] Consider to replace isoinfo by own code rather than by xorriso

[Richard W.M. Jones]

On Sat, Apr 17, 2021 at 06:28:49PM +0200, Thomas Schmitt wrote:
> Hi,
> 
> regarding
>   https://github.com/libguestfs/libguestfs/commit/2f587bbaec718e414e46c7e6f2a3e2662c3a1c2a
> i have to report that the OSDev wiki had a bug about the start address
> of ISO 9660 property Abstract File Identifier.
> 
> I guess that libguestfs' daemon/isoinfo.ml should be changed like this
> 
>   -  let iso_copyright_file_id = sub 702 38 |> iso_parse_strD in
>   -  let iso_abstract_file_id = sub 740 36 |> iso_parse_strD in
>   +  let iso_copyright_file_id = sub 702 37 |> iso_parse_strD in
>   +  let iso_abstract_file_id = sub 739 37 |> iso_parse_strD in

Thanks - I pushed it:

https://listman.redhat.com/archives/libguestfs/2021-April/msg00058.html

Rich.

> Reasoning:
> 
> According to ECMA-119 the field starts at byte offset 739 rather than 740:
>   "8.4.24 Abstract File Identifier (BP 740 to 776)"
> "BP" means Byte Position and begins its counting at 1. So the byte offset
> is one less. The length of the field is 37 bytes, like the length of its
> neighbors.
> 
> For more arguments why the OSDev wiki was wrong, see:
>   https://lists.gnu.org/archive/html/bug-xorriso/2021-04/msg00005.html
> I felt confident enough to make this change in the wiki:
>   https://wiki.osdev.org/index.php?title=ISO_9660&diff=25811&oldid=23724
> 
> 
> Have a nice day :)
> 
> Thomas
> 

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