Use ensure_memoryview in array deserialization

distributed/protocol/serialize.py

@@ -23,7 +23,7 @@
     pack_frames_prelude,
     unpack_frames,
 )
-from distributed.utils import has_keyword
+from distributed.utils import ensure_memoryview, has_keyword
 
 dask_serialize = dask.utils.Dispatch("dask_serialize")
 dask_deserialize = dask.utils.Dispatch("dask_deserialize")
@@ -765,12 +765,11 @@ def _serialize_array(obj):
 @dask_deserialize.register(array)
 def _deserialize_array(header, frames):
     a = array(header["typecode"])
-    for f in map(memoryview, frames):
-        try:
-            f = f.cast("B")
-        except TypeError:
-            f = f.tobytes()
-        a.frombytes(f)
+    nframes = len(frames)
+    if nframes == 1:
+        a.frombytes(ensure_memoryview(frames[0]))
+    elif nframes > 1:
+        a.frombytes(b"".join(map(ensure_memoryview, frames)))
     return a
 
 

distributed/protocol/tests/test_serialize.py

@@ -32,7 +32,7 @@
     to_serialize,
 )
 from distributed.protocol.serialize import check_dask_serializable
-from distributed.utils import nbytes
+from distributed.utils import ensure_memoryview, nbytes
 from distributed.utils_test import gen_test, inc
 
 
@@ -88,19 +88,45 @@ def test_serialize_bytestrings():
         assert bb == b
 
 
+def test_serialize_empty_array():
+    a = array("I")
+
+    # serialize array
+    header, frames = serialize(a)
+    assert frames[0] == memoryview(a)
+    # drop empty frame
+    del frames[:]
+    # deserialize with no frames
+    a2 = deserialize(header, frames)
+    assert type(a2) == type(a)
+    assert a2.typecode == a.typecode
+    assert a2 == a
+
+
 @pytest.mark.parametrize(
     "typecode", ["b", "B", "h", "H", "i", "I", "l", "L", "q", "Q", "f", "d"]
 )
 def test_serialize_arrays(typecode):
-    a = array(typecode)
-    a.extend(range(5))
+    a = array(typecode, range(5))
+
+    # handle normal round trip through serialization
     header, frames = serialize(a)
     assert frames[0] == memoryview(a)
     a2 = deserialize(header, frames)
     assert type(a2) == type(a)
     assert a2.typecode == a.typecode
     assert a2 == a
 
+    # split up frames to test joining them back together
+    header, frames = serialize(a)
+    (f,) = frames
+    f = ensure_memoryview(f)
+    frames = [f[:1], f[1:2], f[2:-1], f[-1:]]
+    a3 = deserialize(header, frames)
+    assert type(a3) == type(a)
+    assert a3.typecode == a.typecode
+    assert a3 == a
+
 
 def test_Serialize():
     s = Serialize(123)