May 1, 2010

Upgraded ZIP Functionality for Web Access

by with 8 comments

We’ve upgraded the zip download in our web shares and web login, and it now creates ZIP64 archives (also sometimes referred to as version 4.5 archives). ZIP64 allows us to create archives with more than 65535 files and archives larger than 4GB.

Unfortunately, not all zip programs support ZIP64. Most notably, Windows XP’s Explorer does not support it. For Windows XP, we recommend using 7-Zip.

ZIP64 has been confirmed to work in OS X 10.6 Finder, Windows Vista/7 Explorer, and Ubuntu 8.10+ Archive Manager (a.k.a. File Roller). It is also supported by Info-Zip 6.0 on the multitude of platforms it supports.

  1. I'm all PRO abandoning XP, but I think this is bad for some non technical users. Why don't you simply check first how many files and what size you have to compress and then decide on the fly? (You could easily make some safe assumptions…)

  2. The main complication is that the code that starts the download doesn't know the size of the total download when it begins. This is because of the zero-knowledge and encryption — the server only decrypts journals as the download is streamed. However, I suspect it might be possible to do Zip64 only when necessary, since the zip info packet is at the end of the archive. We may look into this if people have trouble.

    Previously the biggest source of frustration for users has been attempting to download very large folders that wouldn't fit in the original zip container format.

    We've also had some internal discussion about offering BitTorrent downloads. :)

  3. As Alan said, the zip file is generated on the fly. I believe the magic at the beginning of the file is different for ZIP and ZIP64, meaning we couldn't switch mid-stream. I'm not sure if zip programs are terribly concerned about the magic, but it may confuse the more stupid ones.

  4. Hello,

    First of all, I really like the idea of BitTorrent download functionality that Alan said. I hope you will push through with that project. :)

    Second, I'm just wondering if a feature could be developed whereby folder zips would be replaced by self-extracting archives that automatically extracts the files in the same folder when run, as if choosing to "extract here" the zip. This is how I zip my shared files using ALZip to technical or non technical users.


  5. Yes, we're definitely considering BitTorrent in the future.

    I don't think we want to get into the business of sending EXEs (besides the SpiderOak client, which is signed) from Regular Zips will have to do.

  6. That will also be a problem for non-Windows users ;)
    But Bittorrent is a great idea, Amazon S3 already uses this and it's very useful.