H5D_GATHER retrieves data from a selection within the supplied buffer
src_buf and passes it to the supplied callback function
op in a contiguous form.
src_space_id is a dataspace which defines the extent of
src_buf and the selection within it to gather the data from.
type_id is the datatype of the data to be gathered in both the source and destination buffers.
src_buf must be at least as large as the number of elements in the extent of
src_space_id times the size in bytes of
The data is gathered into
dst_buf, which needs to be large enough to hold all the data if the callback function
op is not provided.
If no callback function is provided, H5D_GATHER