Previously memory that was allocated outside of VTK-m was impossible to transfer to
VTK-m as we didn't know how to free it. By extending the ArrayHandle constructors
to support a Storage object that is being moved, we can clearly express that
the ArrayHandle now owns memory it didn't allocate.
Here is an example of how this is done:
```cpp
T* buffer = new T[100];
auto user_free_function = [](void* ptr) { delete[] static_cast<T*>(ptr); };
vtkm::cont::internal::Storage<T, vtkm::cont::StorageTagBasic>
storage(buffer, 100, user_free_function);
vtkm::cont::ArrayHandle<T> arrayHandle(std::move(storage));
```
Sandia National Laboratories recently changed management from the
Sandia Corporation to the National Technology & Engineering Solutions
of Sandia, LLC (NTESS). The copyright statements need to be updated
accordingly.
The basic storage has an implicit invariant that if the size of the
storage is 0 then the array is a null pointer. That invariant was broken
if the array was allocated and then Shrink or Allocate was called with
0. In that case, the array remained allocated by the size was set to 0.
This fixes the problem by making sure a Shrink(0) actually does an
Allocate(0) (to clear out the data) and that the basic storage always
frees its memory when allocating a 0 sized array.
58bbeb18 Support using empty array handles as input
6d5de0c3 Change make_ArrayHandle work with empty std::vector
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Robert Maynard <robert.maynard@kitware.com>
Merge-request: !694
Previously if you constructed an array handle without allocating it, you
would get an error if you tried to use the array as input. This
conflicted with some recent changes to accept empty vectors.
Now when you try to use an unallocated ArrayHandle as input (calling
PrepareForInput or PrepareForInPlace), it internally calls Allocate(0)
(to establish internal state) and sets up a valid execution ArrayPortal
of size 0.
