Change logic to improve performance

[ardavank]

Thanks for the great tool!
I was using this tool and I noticed that it works great for small unitypackages but it's extremely slow for larger ones.
I improved the performance and wanted to share so that everyone can benefit from it

Results comparison: (using: MacBook Pro - 2.4 GHz 8-Core Intel Core i9)

~ 7 MB unitypackage file:

Before: 6.31 seconds
After: 0.62 seconds

~ 5.52 GB unitypackage file:

Before: I left it running for more than 15 hours and it never finished, had to cancel
After: 71.8 seconds

[Cobertos]

Hmm, I guess it has to dig through the tar's entry table every time it does a getmember() or extractfile() and with 4 hits per entry, that'll be a lot of searching, especially for a 5GB tar...

My only concern with this PR is that if something goes wrong, the temp stuff is not deleted. Itd be preferable if we could use Python's tempfile to handle cases where something fails.

# create a temporary directory using the context manager
>>> with tempfile.TemporaryDirectory() as tmpdirname:
...    print('created temporary directory', tmpdirname)
>>>
# directory and contents have been removed

[ardavank]

I agree, my code might not be production ready, I just wanted to share this with you. feel free to modify and improve it.

[Cobertos]

Closing this, updates are in #6
Thanks for the report and the start on the code :3