Right now ArrowBuf can only point to memory managed by an Arrow Allocator. This is because in many cases we want to be able to support hierarchical accounting of memory and the ability to transfer memory ownership between separate allocators within the same hierarchy.
At the same time, there are definitely times where someone might want to map some amount of arbitrary off-heap memory. In these situations they should still be able to use ArrowBuf.
I propose we have a new ArrowBuf constructor that takes an input that subclasses an interface similar to:
We then make it so all the memory transfer semantics and accounting behavior are noops for this type of memory. The target of this work will be to make sure that all the fast paths continue to be efficient but some of the other paths like transfer can include a conditional (either directly or through alternative implementations of things like ledger).