Re: Where are my bytes hiding?
Re: Where are my bytes hiding?
- Subject: Re: Where are my bytes hiding?
- From: "Gerriet M. Denkmann" <email@hidden>
- Date: Thu, 05 May 2016 18:38:10 +0700
> On 5 May 2016, at 13:13, Stephen J. Butler <email@hidden> wrote:
>
> Those files are compressed by the filesystem. In HFS+/MacOS Extended that means that the data fork is empty and the file contents are stored in the resource fork or extended attributes structure.
>
> http://wiki.sleuthkit.org/index.php?title=HFS#HFS.2B_File_Compression
>
> If it's in the extended attributes, then it's part of the file metadata (like name, timestamps, etc), whereas Finder is probably using the size of the datafork to arrive at 0 bytes. If you get the afsctool (from MacPorts for example) then you can get all sorts of detailed info:
/Applications/Xcode.app/Contents/Developer/Documentation/DocSets/com.apple.adc.documentation.watchOS.docset/Contents/Resources/Tokens/C/tag/-/objc_cache.xml
has indeed 2 extended attributes: com.apple.quarantine and com.apple.decmpfs.
The problem: xattr refuses to show com.apple.decmpfs - even shamelessly lies: “No such xattr: com.apple.decmpfs”.
Good news: listxattr,getxattr do not lie (with XATTR_SHOWCOMPRESSION).
My own tool shows:
com.apple.decmpfs = 895 bytes inline starting with: ‘cmpf’, 3, 0x7d5 = 2005 = uncompressed size, … (small endian ints).
The sum of all decmpfs in the folder is 4057 bytes - still no idea how Finder gets its: “29 KB on disk” .
Kind regards,
Gerriet.
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