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Re: finding the offset of a partition

Subject: Re: finding the offset of a partition
From: Rick Sulack <email@hidden>
Date: Fri, 3 Feb 2006 11:22:23 -0800
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On Feb 3, 2006, at 8:40 AM, Jason Bobier wrote:

In the driver, the disk and the partition are represented by IOMedia objects and you can use getBase on the partition to know where it is relative to the disk. So the system knows how the two are related.

I'm trying to get the offset on disk of a particular file. In order to do this I use F_LOG2PHYS which gives me the offset from the beginning of the partition. So I need to add the partition offset somehow.

IMHO, this is bad idea. What happens if the file turns out to be on striped RAID volume?

Also, there are many different types of partitioning schemes that Mac OS X supports, but I don't believe there is any API that you could use for generically finding the start of a partition on each one. I only see sizes in the IO Registry for partitions.

I think you are better off using the offset from the start of the partition.

-rick

Thanx,
Jason
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Jason Bobier            email@hidden
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On Feb 2, 2006, at 11:28 PM, Justin C. Walker wrote:
On Feb 2, 2006, at 22:49 , Jason Bobier wrote:
I can't seem to find a way to find the offset of a partition on a drive without reading the partition table myself. Is there an easy way to do this?

i.e. given disk1s1 what is it's offset from the beginning of disk1?
AFAIK, there is nothing intrinsic about partitions. It's the partition table that defines them. That's what the system uses to find them, when partitions on a disk are mounted. Why do you think it's otherwise possible?
Regards,
Justin
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Justin C. Walker, Curmudgeon-At-Large
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References:
	>finding the offset of a partition (From: Jason Bobier <email@hidden>)
	>Re: finding the offset of a partition (From: "Justin C. Walker" <email@hidden>)
	>Re: finding the offset of a partition (From: Jason Bobier <email@hidden>)

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