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

[Thomas Schmitt]

Hi,

Richard W.M. Jones wrote:
> "megabytes" may not be a problem - and in fact hasn't been in my
> testing.  Could it grow unbounded?

It depends on the number of files, the lengths of the file names,
and the amount of some other meta data in the tree.
So if malice is involved: Yes, it can become nasty.

In a backup ISO with 78478 files with conservative names i see about 17 MB
of directory tree (because the first data content starts at LBA 8613).
The memory representation of the tree in libisofs underneath xorriso will
need some extra bytes per file as overhead.
ps -o rsz,vsz of the process shows the numbers 47880  67136 with a
dynamically linked Debian binary of xorriso, and 73836  99844 with my
statically linked development version of GNU xorriso.

The run time of -indev with this ISO from RAM cache is about 0.5 seconds
on a not really young 3.5 GHz Xeon system.

Direct reading of the PVD would just need to load 2048 bytes from LBA 16
and to pick from byte fields at well documented locations the strings (with
trailing blanks) and numbers (with both endianesses).


Have a nice day :)

Thomas