Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!shelby!polya!kaufman
From: kaufman@polya.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Missing megabytes
Message-ID: <7550@polya.Stanford.EDU>
Date: 9 Mar 89 17:48:16 GMT
References: <457@sys.uea.ac.uk>
Sender: Marc T. Kaufman <kaufman@polya.Stanford.EDU>
Reply-To: kaufman@polya.Stanford.EDU (Marc T. Kaufman)
Organization: Stanford University
Lines: 18

In article <457@sys.uea.ac.uk> jrk@s1.UUCP (Richard Kennaway) writes:
>I am writing a program which, among other things, makes a directory
>listing of a volume.  There is a strange discrepancy in the
>information it collects.

>When it scans through all the files and folders with PBHGetCatInfo
>in the usual way, it always finds exactly the right number of files and
>folders, but the sum of their sizes is sometimes less than the
>calculated number of used blocks.

You should be aware that disk space is allocated in "Clumps" of size ioVClpSiz,
where the clump size is chosen so that [disk size / clump size] < 65535,
which is the maximum number of allocation blocks that the file system can
handle.  In addition, there is overhead for the allocation block bit map and
the allocation and directory B-trees, which will not be reflected in the
simple summation of file sizes.

Marc Kaufman (kaufman@polya.stanford.edu)