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Date: Sat, 23 Aug 2008 10:54:54 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Rogier Wolff <R.E.Wolff@bitwizard.nl>
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On Sat, 23 Aug 2008, Rogier Wolff wrote:
>
>> For example,
>> Apple OS-X's HFS+ does not support holes.
>
> Weird. So, will my suggested code fail? No.

OS-X's HFS+ will simply consume the space with zeros.

>> Windows FAT type
>> filesystems (still very much in use in millions of systems/devices) do
>> not support holes.
>
> Correct. But will my code fail? No. It does skip the copying of
> "zeroes" from userspace into the kernel. Wether this will in fact
> increase or decrease perfomance when all things are added up, I don't
> know.

The code may very well fail.

> It is likely that you don't know that the posix specifications are
> pretty clear about this.
>
> If I program
>
> 	main (int argc, char **argv)
> 	{
> 		int a;
> 		int b;
> 		a = 3;
> 		b = 5;
> 		printf ("%d\n", a+b);
> 	}
>
> the output should be "8". This is because I used standard features of
> a standard programming language. Opening and writing files goes a bit

You are communicating with someone who has used and programmed "unix" 
for twenty years now.  The above was not called for.

Bob
======================================
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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