open_split_region
def open_split_region(path: String, size: Int) -> BumpAllocator[MappedRegion]A mapping at path, sized for everything about to go into it.
arrow_mlake.memory_shim
Opening a region, for a caller that does not want the allocator's types.
export_shared_into takes a BumpAllocator[MappedRegion], which a tool would
otherwise have to name — and naming it means importing memory_region just to
spell a parameter. This is the one line that saves every publisher from that.