Re: [rvm-research] AddressArray with CAS

On 5/29/2013 11:01 AM, Nachshon Cohen O wrote:
> Hi
>
> I'm trying to use a wait free queue implementation in the Jikes RVM.
> The implementation holds an array of addresses, and I'd like to apply CAS (compareAndSet) to these addresses.
> For example:
> AddressArray arr = AddressArray.create(10);
> arr[ 3 ].compareAndSet(oldValue, newValue);
>
> It seems that unboxed.AddressArray does not have an option of CAS.
> A normal CAS is implemented only for objects: i.e. Magic.attemptAddress(object, offset, oldValue, newValue);
> However, I don't know how to convert the AddressArray to an object.
>
> Is there a way to use CAS on a specific array element?

An AddressArray is a perfectly good object.  The offset of element
0 is 0 (by design, so that we do not need to add an extra constant
value in for every array access).  You need to know the size of an
Address, but I think there are operations for converting an array
index into an offset, etc.  You also need to be careful not to
access outside the bounds of the actual array, of course.

Regards -- Eliot Moss

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