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7-Zip 25.00

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Re: 7-Zip 25.00

#21

Post by duskwuff »

mikepurvis wrote: post #19
nine_k wrote: post #16

Earlier quoted context omitted.

Decompress, scan as you go, discard. Having to read a few hundred GB and scan a terabyte is a nuisance. Not having to write a terabyte is priceless.

Could also maintain an in-memory index so that you can go back after the fact and extract individual files.

That's less helpful than you might imagine - gzip isn't seekable by default; if all you know is the seek point, you still have to decompress everything up to that point to start decompressing from there. And if you have to do that, reading the tar headers as you go isn't a serious burden.

What might help is saving the state of the decompressor periodically, rather than just the index in the file. But that's getting pretty far into the weeds for an optimization to an infrequently used feature.

Re: 7-Zip 25.00

#22

Post by Dwedit »

blibble wrote: post #14
gertop wrote: post #13

I wish 7-zip would support .tar.gz the way WinRAR does. WinRAR allows you to browse a .tar.gz without extracting it, 7-zip extracts the .tar to a temp file. It makes working with large .tar.gz files impossible. (Yes I know that because of how .tar works WinRAR must decompresses it to build the files list. But it beats having to write a 1TB .tar to disk just to see the file listing.

how is that possible? tar.gz files don't have a central directory (like zip), and they are compressed as one stream (almost always non-seekable)

.tar itself gives you enough information to seek forward past each file, though every file must be visited.

.gz does not give you enough information to randomly seek within the big compressed .gz file, so you cannot skip past files within a .tar archive.

But if you load a .gz file and consume the entire stream, but keep periodic checkpoints of your past sliding window (about 64KB) every 1MB or so, you can get random access with 1MB granularity. You still had to consume the entire stream to build the lookup though.

Re: 7-Zip 25.00

#23

Post by Dwedit »

7-Zip 15.05 is still useful today, because it was the last version to include built-in support for decompiling NSIS installer scripts. The feature was removed due to security concerns.

Re: 7-Zip 25.00

#24

Post by genocidicbunny »

gertop wrote: post #13

I wish 7-zip would support .tar.gz the way WinRAR does. WinRAR allows you to browse a .tar.gz without extracting it, 7-zip extracts the .tar to a temp file. It makes working with large .tar.gz files impossible. (Yes I know that because of how .tar works WinRAR must decompresses it to build the files list. But it beats having to write a 1TB .tar to disk just to see the file listing.

WinRAR also seems to handle opening a file in an external app without manually extracting much better. I can just double-click a file in an archive and open it in an external app, while with 7-zip it seems to immediately delete the temporary file so the external app ends up trying to open a non-existent file. Rather annoying if you're just trying to quickly check something like the readme.txt in an archive.

Re: 7-Zip 25.00

#25

Post by genocidicbunny »

jchw wrote: post #8
doctorpangloss wrote: post #2

Why doesn't Windows ship with an unarchiving utility?

Windows has shipped with "ZIP folders" and the ability to create and extract ZIP files since the late 90s/early 2000s I believe (not sure exactly what version.) As of the latest versions of Windows 11, Windows ships with libarchive-based archive extraction, which should let you extract many archives natively (including 7-zip and RAR) via the UI as well as the CLI (via BSD TAR, which also ships with Windows these days…

I think those first appeared in some form in XP. I don't recall 2000 having support for it integrated into explorer.

Re: 7-Zip 25.00

#26

Post by parlortricks »

Dwedit wrote: post #23

7-Zip 15.05 is still useful today, because it was the last version to include built-in support for decompiling NSIS installer scripts. The feature was removed due to security concerns.

Why is decompiling NSIS a security concern?

Re: 7-Zip 25.00

#27

Post by Dwedit »

jchw wrote: post #8
doctorpangloss wrote: post #2

Why doesn't Windows ship with an unarchiving utility?

Windows has shipped with "ZIP folders" and the ability to create and extract ZIP files since the late 90s/early 2000s I believe (not sure exactly what version.) As of the latest versions of Windows 11, Windows ships with libarchive-based archive extraction, which should let you extract many archives natively (including 7-zip and RAR) via the UI as well as the CLI (via BSD TAR, which also ships with Windows these days…

ZIP Folders was developed by Dave Plummer from Microsoft (who runs the Dave's Garage YouTube channel). It was made in his spare time, then was licensed to Microsoft afterwards.

Re: 7-Zip 25.00

#28

Post by Dwedit »

parlortricks wrote: post #26
Dwedit wrote: post #23

7-Zip 15.05 is still useful today, because it was the last version to include built-in support for decompiling NSIS installer scripts. The feature was removed due to security concerns.

Why is decompiling NSIS a security concern?

In case of bugs in the decompiler. Extracting the files is still possible in newer versions, just not decompiling the installer scripts.

Re: 7-Zip 25.00

#29

Post by NooneAtAll3 »

Dwedit wrote: post #23

7-Zip 15.05 is still useful today, because it was the last version to include built-in support for decompiling NSIS installer scripts. The feature was removed due to security concerns.

what is NSIS?
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