How to allocate 4GB in a plug-in

Question

Hi,
I'm working on a filter plug-in which someone wants to use to process really large 32-bit files (e.g. 550+ megapixels).  Apparently they can load these info Photoshop 64-bit (I'd like to have enough RAM to be able to try this).  But the plug-in needs to allocate scratch buffers for processing, equal to more than twice the image size, and for images this size, this means allocating more than 4GB in the plug-in, and more than 2GB in one hit.
The way I'm currently doing this doesn't work for images of this size for two reasons:
1. I seem to have to set the bufferSpace field in the FilterRecord structure to the amount of buffer I want to allocate, when allocating large amounts, or calls to allocateProc fail.  However bufferSpace seems to be an int32 (typedef for long, which is 32 bits even on a 64-bit machine apparently).  How can I indicate to Photoshop that my plug-in will be asking for more than 4GB of RAM?  (Given that int32 is signed, I'm not sure I can tell it I'll be asking for more than 2GB in fact.)
2. I want to allocate, say 2.2GB using allocateProc, but it also takes a signed int32 as a parameter, suggesting that 2GB would be the maximum amount I could allocate in one go, and certainly 4GB even if it treated it as unsigned internally.
So I'd like to know if there are 64-bit friendly versions of bufferSpace and allocateProc that I can use when memory requirements are large?  If the int32 versions are all there are, it would seem like a serious limitation on the way 64-bit plug-ins can use RAM.
Thanks
                -Matthew

Answer 1

If you think you need to allocate the whole image at one time, much less multiple copies of the whole image -- you're doing it wrong.
Rethink the problem so you can work in strips or tiles.