if numpy is found during configure then libsim may be passed
numpy arrays directly. zero-copy transfer are supported via
numpy c-api. a new ownership type is introduced to support
safe zero-copy transfer of data to vtk data arrays. when this
ownership is requested a custom (potentially user provided)
callback is invoked by an internally arranged observer of vtk
data array delete event. the callback should free the memory.
this mechanism can be used in any zero-copy transfer through
libsim where c's free is not the correct function to free the
transfered memory, in the case of python and numpy, we make
use of python's ref counting to ensure the numpy object is not
destroyed until the vtk array is deleted. the numpy object's
ref count incremented (by libsim) as its passed in, libsim
provides a callback which decrements the object's ref count
when the vtk data array is deleted. aside from having to pass
the new ownership flag, this all happens transparently to the
user as it is implemented in libsim's python swig customizations.
If this were to be used in other situations, eg FORTRAN, the user
would be extected to provide the memory management callback.



git-svn-id: http://visit.ilight.com/svn/visit/trunk/src@22880 18c085ea-50e0-402c-830e-de6fd14e8384