dims = [100 200];
h5_dims = fliplr(dims);
space_id = H5S.create_simple(2,h5_dims,h5_dims);
op = 'H5S_SELECT_SET';
start = fliplr([10 20]); block = fliplr([20 30]);
H5S.select_hyperslab(space_id,'H5S_SELECT_SET',start,[],[],block); 
n = H5S.get_select_npoints(space_id);