I've just released v.2.5, found here:
This release includes SHA256Digest_MTC and SHA512Digest_MTC classes that will let you calculate those respective hashes in blocks.
A note about those optimizations. Anyone looking to this project as an example of how to properly code in Xojo shouldn't. In order to achieve the best speed, I've written the code in a way that would make kittens cry, getting as close to the metal as Xojo allows. I've eliminated as many function and method calls as I could by manually inlining code, avoided arrays by using MemoryBlocks, and used Ptr rather than the MemoryBlock functions wherever possible even when I had to manually flip byte order.
On the other hand, if you want an example of how to get the best possible speed regardless of readability or maintainability, this will do.