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Re: Address alignment
On Sat, Jan 09, 2010 at 05:46:05PM +0000, Sad Clouds wrote:
> Hi, I have a requirement where I'm writing N bytes of data to a buffer. If
> last byte after data is not aligned on 8-byte boundary, I need to add some
> padding after data.
> So assume 'buffer' is a pointer to a buffer, after putting N bytes of data in
> the buffer the pointer will be incremented by N. Is the following code
> for aligning a pointer on 8-byte boundary? Will it work correctly with 64-bit
> addresses, or do I need to cast -8 to 64-bit value in that case?
> buffer & -8
You can't use '&' on pointers, and that isn't quite the right expression.
The one you want is: x = (x + 7) & ~7;
With a pointer there are varios options, casting to uintptr_t
is one one the easiest.
David Laight: david%l8s.co.uk@localhost
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