Filed under: OS, Apple, Developer
Xar
The Leopard news of the moment is that Xar will be baked in. Xar, or eXtensible ARchive format, is just what it sounds like, a new way to compress files. You're thinking, 'Aren't there lots of ways to do this already?' Yes, but as this page entitled 'Why xar is interesting' explains Xar has some big things going for it. Firstly, it keeps metadata (like file type, MP3 data, and the like) in a separate file so you can tell lots about a compressed file without having to uncompress it. It also compressed each file separately, so if you Xar a folder each file is compressed separately.Xar is already available for download, if the more technical amongst you would like to take it for a spin.
Pretty neat.
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Reader Comments (Page 1 of 1)
Michael Murphey said 9:39PM on 12-31-2006
It will be interesting to see how Xar is utilized in the future. It looks very promising.
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daniel tucker said 9:45PM on 12-31-2006
this bit caught my eye
"Files in xar are individually compressed. This allows for quick extraction of individual files without the extra disk space requirements and CPU usage of extracting the entire archive, as compared to a compressed tar archive. This makes xar useful for quick restores of accidentally deleted or overwritten files, from a backup archive. Additionally, this means xar can use different compression methods for each file in the archive. For instance, it might not be a good idea to try to try to compress an already compressed file, but a large file might benefit greatly from using bzip2, whereas a small text file would be better served to use gzip."
It makes sense for xar to be a format to help keep file sizes down in Time Machine.
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Erik said 10:58PM on 12-31-2006
Ok. So, what does XAR provide (other than being bult-in), that Stuffit DropStuff doesn't? DropStuff can compress each file in an archive individually, and apply different compression levels to each file, based on analysis. Also, I have never heard of XAR before, and would have to guess that it is a proprietary (if open-source) format, and therefore will not be compatible with the existring file extraction software that is currently available. Please correct me, if I am wrong on this.
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Leonard Nimrod said 11:45PM on 12-31-2006
I think Dan Tucker is dead on balls. It's looks lik,e a great fit for TimeMachine.
Erik, you may want to read the page below on XAR.
"Xar's XML header allows it to contain arbitrary metadata about files contained within the archive. In addition to the standard unix file metadata such as the size of the file and it's modification and creation times, xar can store information such as ext2fs and hfs file bits, unix flags, references to extended attributes, Mac OS X Finder information, Mac OS X resource forks, and hashes of the file data. But that is just the beginning of the possibilities."
http://www.opendarwin.org/~bbraun/whyxar.html
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Jim M. said 11:56PM on 12-31-2006
Gee Erik, your name links to the StuffIt commercial site. Could you be any more blatant in your hawking of the way-past-its-prime (truly) proprietary StuffIt technology?
Oh, you might want to look up the work "proprietary" before you use it again.
xar looks really promising to me. It's no wonder that you StuffIt folks are trying to put a negative spin on it already.
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gregday said 12:10AM on 1-01-2007
Erik, you are completely backwards. StuffIt is one of the most closed, proprietary formats in the world, and there is no reason for anyone to use it at all. Xar is like a beefed up Tar, and it's all completely open source -- nothing about it is proprietary. That's kind of impossible, proprietary and open source are antonyms. Leopard build 9A321 already includes the xar command line utility to work with them, and anyone can build the xar and libxar source on any Unix platform. I'm sure any important packaging software can and will be updated easily.
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Leonard Nimrod said 12:25AM on 1-01-2007
From a switchers standpoint, StuffIT may look like a godsend. I'm guessing this is the POV Erik is coming from.
Happy New Year!
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Leonard Nimrod said 12:26AM on 1-01-2007
PS: How lame am I for readin TUAW at midnight on NYE? Can I at least get a "pity" star for being so pathetic?
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Vincent said 5:06AM on 1-01-2007
Xar, an archive system for Mail.app?
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Edward C said 10:21AM on 1-01-2007
I think Xar is more like a container format for all other stuff. It could use 7zip, or what ever compression method that is good for the file and allows you to view description of files stored in XML without extracting it.
All in all i think it is pretty neat stuff. Would be nice if Xar choose to officially support a few compression like gzip and 7zip :)
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Rich said 3:22PM on 1-01-2007
Xar - pronounced Zar or Ex-ar ?
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Extensor said 5:15PM on 1-01-2007
@#8 Nimrod: Here, you can borrow my star. and Happy New Year!
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Steven said 1:53AM on 1-02-2007
eh
disk space is cheap....I have close to 2 terabytes in my bedroom....if i actually want to compress stuff, i want block compression where all files are compressed together for maximum savings, more rar/7zip/targz, less zip
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Jeem said 4:27PM on 1-02-2007
I doubt the page is entitled to anything. Hey, I'm titled to my opinion!
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