Re: Difference between dvd and dmg
Re: Difference between dvd and dmg
- Subject: Re: Difference between dvd and dmg
- From: "Gerriet M. Denkmann" <email@hidden>
- Date: Sun, 23 Oct 2005 22:10:13 +0200
On 23.10.2005, at 20:02, j o a r wrote:
On 12 okt 2005, at 18.54, Gerriet M. Denkmann wrote:
This is correct. So the question should be:
When one opens a raw device via open(/dev/rdisk...) how does one get
the hardware sector size (which in this case is needed for read or
pread)?
It seems to be 512 for disks, 2048 for rotating media. But maybe
there is something better than trial and error?
You can get this value from IOKit fairly easily, using
"kIOMediaSizeKey".
I looked up kIOMediaSizeKey:
#define kIOMediaSizeKey "Size"
The kIOMediaSizeKey property has an OSNumber value and describes the
total length of the media in bytes.
So maybe "Size" is not really what I am interested in.
But I found another property: kIOMediaPreferredBlockSizeKey =
"Preferred Block Size" which is 512 for my hard disk, and 2048 for a CD
with HFS+.
"The kIOMediaPreferredBlockSizeKey property has an OSNumber value and
describes the media's natural block size in bytes. This information is
useful to clients that want to optimize access to the media."
Is there a "fairly easy" way to get the appropriate IOKit dictionary
from a bsd-name (like /dev/rdisk1s2) ?
Kind regards,
Gerriet.
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