Bug fix in h5::array_interface

c++/h5/array_interface.cpp

@@ -77,9 +77,6 @@ namespace h5::array_interface {
     // create the result vectors
     v_t parent_shape(rank), h5_strides(rank);
 
-    // from the above equations it follows that parent_shape[0] (size of the slowest varying dimension) is arbitrary
-    parent_shape[0] = view_size;
-
     // We initialize the h5_strides array to the values of np_strides
     // and successively divide off the parent_shape values as they appear
     // in the equations above.
@@ -91,6 +88,10 @@ namespace h5::array_interface {
       for (int v = u; v >= 0; --v) { h5_strides[v] /= gcd; }
     }
 
+    // from the above equations it follows that parent_shape[0] (size of the slowest varying dimension)
+    // is arbitrary as long as it is big enough to contain the elements selected by the hyperslab
+    parent_shape[0] = view_size * h5_strides[0];
+
     return {parent_shape, h5_strides};
   }
 

test/c++/h5_array_interface.cpp

@@ -49,7 +49,7 @@ void check_strides(const std::vector<long> &np_strides, const std::vector<long>
   for (int i = static_cast<int>(np_strides.size()) - 1; i >= 0; --i) {
     EXPECT_EQ(np_strides[i], product * h5_strides[i]);
     product *= parent_shape[i];
-    EXPECT_TRUE(parent_shape[i] >= view_shape[i]);
+    EXPECT_TRUE(parent_shape[i] >= view_shape[i] * h5_strides[i]);
   }
 }