Merge pull request #724 from effigies/test/array_seq_extension

RF: Use safe resizing for ArraySequence extension

Author: effigies

nibabel/streamlines/array_sequence.py

@@ -23,6 +23,16 @@ def is_ndarray_of_int_or_bool(obj):
             np.issubdtype(obj.dtype, np.bool_)))
 
 
+def _safe_resize(a, shape):
+    """ Resize an ndarray safely, using minimal memory """
+    try:
+        a.resize(shape)
+    except ValueError:
+        a = a.copy()
+        a.resize(shape, refcheck=False)
+    return a
+
+
 class _BuildCache(object):
     def __init__(self, arr_seq, common_shape, dtype):
         self.offsets = list(arr_seq._offsets)
@@ -196,7 +206,7 @@ def _resize_data_to(self, n_rows, build_cache):
         if self._data.size == 0:
             self._data = np.empty(new_shape, dtype=build_cache.dtype)
         else:
-            self._data.resize(new_shape)
+            self._data = _safe_resize(self._data, new_shape)
 
     def shrink_data(self):
         self._data.resize((self._get_next_offset(),) + self.common_shape,

nibabel/streamlines/tests/test_array_sequence.py

@@ -219,6 +219,10 @@ def test_arraysequence_extend(self):
         seq = SEQ_DATA['seq'].copy()  # Copy because of in-place modification.
         assert_raises(ValueError, seq.extend, data)
 
+        # Extend after extracting some slice
+        working_slice = seq[:2]
+        seq.extend(ArraySequence(new_data))
+
     def test_arraysequence_getitem(self):
         # Get one item
         for i, e in enumerate(SEQ_DATA['seq']):