Implement VDS interface about h5cpp HOT 2 CLOSED

To implement VDS the following classes need modification

• DatasetAccessList
• and DatasetCreationList

The DatasetLayout enumeration has already a VIRTUAL entry to create a virtual dataset.
DatasetCreationList is where most of the configuration work is done.
There are certain boundary conditions we have to take into account

• all mappings must be done during creation of the dataset (they are added to the DatasetCreationList.
  We thus cannot modify the mappings once the dataset is created.
• as a consequence of the brevious item we only can read the mappings from a dataset once it is
  created.

Additional classes

VirtualDataMap

This class describes the mapping between the virtual dataset and the actual data. This information
includes

• a Selection in the dataspace of the virtual dataset
• a boost::filesystem::path to the source file
• a hdf5::Path to the dataset within the source file
• a Dataspace and Selection in the source dataset

VirtualDataset class

Implementing this feature may be also a good use case to test object instantiation with constructors.
It would make sense to derive a class VirtualDataset from Dataset which has a special
constructor only taking those arguments relevant for constructing a virtual dataset (we do not need
filters for instance).

from h5cpp.

We may want to store VirtualDataMap instances in a container thus the class must satisfy all requirements such a
container makes on an element type

• default constructible
• copy constructible

This has consequences for those members of VirtualDataMap which rely on virtual functions to operate correctly.
For such members we need smart pointers as references would not work (cannot be default constructed).

from h5cpp.