Merge pull request #593 from jstutters/avoid-extra-padding

Stop adding extraneous metadata padding

Author: effigies

nibabel/nifti1.py

@@ -334,7 +334,8 @@ def get_sizeondisk(self):
         size = len(self._mangle(self._content))
         size += 8
         # extensions size has to be a multiple of 16 bytes
-        size += 16 - (size % 16)
+        if size % 16 != 0:
+            size += 16 - (size % 16)
         return size
 
     def __repr__(self):

nibabel/tests/test_nifti1.py

@@ -1075,6 +1075,9 @@ def test_extension_basics():
     assert_true(ext.get_sizeondisk() == 16)
     assert_true(ext.get_content() == raw)
     assert_true(ext.get_code() == 6)
+    # Test that extensions already aligned to 16 bytes are not padded
+    ext = Nifti1Extension('comment', b'x' * 24)
+    assert_true(ext.get_sizeondisk() == 32)
 
 
 def test_ext_eq():