FIX: Immutable buffers should not be set writeable

Author: effigies

nibabel/streamlines/tck.py

@@ -432,10 +432,8 @@ def _read(cls, fileobj, header, buffer_size=4):
                 for point_part in point_parts:
                     # Read floats.
                     pts = np.frombuffer(point_part, dtype=dtype)
-                    # Enforce ability to write to underlying bytes object
-                    pts.flags.writeable = True
                     # Convert data to little-endian if needed.
-                    yield pts.astype('<f4', copy=False).reshape([-1, 3])
+                    yield pts.astype('<f4').reshape([-1, 3])
 
                 n_streams += len(point_parts)
 

nibabel/streamlines/tests/test_trk.py

@@ -105,8 +105,7 @@ def trk_with_bytes(self, trk_key='simple_trk_fname', endian='<'):
         with open(DATA[trk_key], 'rb') as fobj:
             trk_bytes = fobj.read()
         dt = trk_module.header_2_dtype.newbyteorder(endian)
-        trk_struct = np.ndarray((1,), dt, buffer=trk_bytes)
-        trk_struct.flags.writeable = True
+        trk_struct = np.ndarray((1,), dt, buffer=trk_bytes).copy()
         return trk_struct, trk_bytes
 
     def test_load_file_with_wrong_information(self):

nibabel/volumeutils.py

@@ -538,9 +538,13 @@ def array_from_file(shape, in_dtype, infile, offset=0, order='F', mmap=True):
                           n_read,
                           getattr(infile, 'name', 'object')))
     arr = np.ndarray(shape, in_dtype, buffer=data_bytes, order=order)
+    if not needs_copy:
+        try:
+            arr.flags.writeable = True
+        except ValueError:
+            needs_copy = True
     if needs_copy:
-        return arr.copy()
-    arr.flags.writeable = True
+        arr = arr.copy()
     return arr