Add the missing buffer_callback argument (#308)

Co-authored-by: Olivier Grisel <olivier.grisel@ensta.org>

CHANGES.md

@@ -19,6 +19,10 @@
   over the module list
   ([PR #322](https://github.com/cloudpipe/cloudpickle/pull/322)).
 
+- Add support for out-of-band pickling (Python 3.8 and later).
+  https://docs.python.org/3/library/pickle.html#example
+  ([issue #308](https://github.com/cloudpipe/cloudpickle/pull/308))
+
 1.2.2
 =====
 

cloudpickle/cloudpickle_fast.py

@@ -34,7 +34,7 @@
 
 
 # Shorthands similar to pickle.dump/pickle.dumps
-def dump(obj, file, protocol=None):
+def dump(obj, file, protocol=None, buffer_callback=None):
     """Serialize obj as bytes streamed into file
 
     protocol defaults to cloudpickle.DEFAULT_PROTOCOL which is an alias to
@@ -44,10 +44,10 @@ def dump(obj, file, protocol=None):
     Set protocol=pickle.DEFAULT_PROTOCOL instead if you need to ensure
     compatibility with older versions of Python.
     """
-    CloudPickler(file, protocol=protocol).dump(obj)
+    CloudPickler(file, protocol=protocol, buffer_callback=buffer_callback).dump(obj)
 
 
-def dumps(obj, protocol=None):
+def dumps(obj, protocol=None, buffer_callback=None):
     """Serialize obj as a string of bytes allocated in memory
 
     protocol defaults to cloudpickle.DEFAULT_PROTOCOL which is an alias to
@@ -58,7 +58,7 @@ def dumps(obj, protocol=None):
     compatibility with older versions of Python.
     """
     with io.BytesIO() as file:
-        cp = CloudPickler(file, protocol=protocol)
+        cp = CloudPickler(file, protocol=protocol, buffer_callback=buffer_callback)
         cp.dump(obj)
         return file.getvalue()
 
@@ -421,10 +421,10 @@ class CloudPickler(Pickler):
     dispatch[types.MappingProxyType] = _mappingproxy_reduce
     dispatch[weakref.WeakSet] = _weakset_reduce
 
-    def __init__(self, file, protocol=None):
+    def __init__(self, file, protocol=None, buffer_callback=None):
         if protocol is None:
             protocol = DEFAULT_PROTOCOL
-        Pickler.__init__(self, file, protocol=protocol)
+        Pickler.__init__(self, file, protocol=protocol, buffer_callback=buffer_callback)
         # map functions __globals__ attribute ids, to ensure that functions
         # sharing the same global namespace at pickling time also share their
         # global namespace at unpickling time.

tests/cloudpickle_test.py

@@ -2052,6 +2052,22 @@ def __getattr__(self, name):
         with pytest.raises(pickle.PicklingError, match='recursion'):
             cloudpickle.dumps(a)
 
+    def test_out_of_band_buffers(self):
+        if self.protocol < 5:
+            pytest.skip("Need Pickle Protocol 5 or later")
+        np = pytest.importorskip("numpy")
+
+        class LocallyDefinedClass:
+            data = np.zeros(10)
+
+        data_instance = LocallyDefinedClass()
+        buffers = []
+        pickle_bytes = cloudpickle.dumps(data_instance, protocol=self.protocol,
+                                         buffer_callback=buffers.append)
+        assert len(buffers) == 1
+        reconstructed = pickle.loads(pickle_bytes, buffers=buffers)
+        np.testing.assert_allclose(reconstructed.data, data_instance.data)
+
 
 class Protocol2CloudPickleTest(CloudPickleTest):