Prevent integer overflow in NodeManager and LeafManager

[ghurstunither]

For large enough grids, leafCounts in initLeafArray() and nodeCounts in initNodeChildren() can overflow as std::vector<Index32>.

[ghurstunither]

Needs a change for the log

Is that something I add in this PR?

would be ideal if we could add a simple unit test that exceeds 32-bit integer.

I'm not sure how to do that without making a gigantic tree.

[danrbailey]

I think there's actually more to talk about here. The Tree and RootNode also make assumptions that the number of leaf nodes cannot exceed 2^32:

https://github.com/AcademySoftwareFoundation/openvdb/blob/master/openvdb/openvdb/tree/Tree.h#L116

The tree ones in particular are actually virtual functions, so if we want to bump this arbitrary limit, we should also change those methods as an ABI change.

[ghurstunither]

I think there's actually more to talk about here. The Tree and RootNode also make assumptions that the number of leaf nodes cannot exceed 2^32:

https://github.com/AcademySoftwareFoundation/openvdb/blob/master/openvdb/openvdb/tree/Tree.h#L116

The tree ones in particular are actually virtual functions, so if we want to bump this arbitrary limit, we should also change those methods as an ABI change.

Thanks for pointing this out. I think the following should return Index64:

• unallocatedLeafCount
• leafCount
• nodeCount

The other methods seem fine to return Index32 if we assume we'll never exceed 2^32 for other nodes, which I think is reasonable.