The rearguard idea is appealing.
The extractions currently use Archive::Unzip::Burst as the first
attempt. I don't know its behaviour, but I assume that if some files
exist and are locked then it will fail. In that event the approach
switches to iterating over $zip->memberNames, so it will still work.
(Actually, Archive::Unzip::Burst seems not to install on Windows, so the
latter approach will be the norm on that OS).
Of course, this won't fix the issues where files are cleaned up while a
PAR is running process, so some sort of API sub would still be useful to
allow scripts to re-extract if file opens fail. This would not be
simple to apply where file opens are called deep inside third party
modules, but will still benefit the simpler cases.
WRT the different cache areas, PAR::_extract_inc currently spends up to
10 seconds trying to create a lock file, so that line needs to be
modified. Adding a check for -w on the target temp location should be
enough to avoid that when the exe file is in a non-writable directory.
Apart from possible security issues, this approach could also lead to
multiple par temp folders which could confuse users. Of course, being
"up front" about files could be a useful thing to do.
Regards,
Shawn.
On 18/12/2014 19:02, Roderich Schupp wrote:
Here are two other ideas for a workaround for "some cleanup program
purged some files in my cache area".
The rearguard hack:
* make sure extracted files get the timestamp of extraction, not the
timestamp recorded in the zip archive
* add a dummy file, say REARGUARD.txt, at the top of the cache area
* extract it as the first file (so that it becomes the oldest
extracted file)
* at packed executable startup, check that REARGUARD.txt exists,
otherwise re-extract all files
Different location for the cache area:
* when the packed executable foo.exe is installed as
/some/path/foo.exe, extract to /some/path/foo.unpacked if this
directory can be created
* otherwise fall back to current behaviour, ie. extract to $TMP/par-USER
* I'm not sure about the security implications
Cheers, Roderich
--
Assoc Prof Shawn Laffan
School of Biological, Earth and Environmental Sciences
UNSW, Sydney 2052, Australia
Tel +61 2 9385 8093 Fax +61 2 9385 1558
http://www.bees.unsw.edu.au/staff/shawn-laffan
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