Handle (new) buffer protocol conforming types in Pickle.decode
#143
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On Python 3, `pickle.loads` is able to work with anything that supports the (new) buffer protocol. Unfortunately Python 2's, `cPickle.loads` is not so flexible and requires a `bytes` object specifically. So this ensures that other objects are coerced to `bytes` objects specifically on Python 2.
On Python 3, `pickle.loads` expects an object that implements the buffer protocol and is contiguous. While it would already raise this error, it helpful for us to check this first. Plus we should be able to handle Fortran order buffers should that be needed. On Python 2, the more strict constraint of a `bytes` object is required, which is still enforced.
This ensures that Pickle can decode anything that supports the (new) buffer protocol.
jakirkham
commented
Nov 30, 2018
| if PY2: | ||
| buf = ensure_bytes(buf) | ||
| else: | ||
| buf = ensure_contiguous_ndarray(buf) |
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Just to provide context from the Python codebase, Python 2 requires bytes here and Python 3 uses the (new) buffer protocol to get a C-contiguous array.
jakirkham
commented
Nov 30, 2018
| @@ -147,6 +147,10 @@ def check_encode_decode_array(arr, codec): | |||
| codec.decode(enc, out=out) | |||
| assert_array_items_equal(arr, out) | |||
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| enc = codec.encode(arr) | |||
| dec = codec.decode(ensure_ndarray(enc)) | |||
| assert_array_items_equal(arr, dec) | |||
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Seems this worked for everything except Pickle on Python 2 as demonstrated by this CI failure. This is likely a consequence of the improved buffer handling under the hood, which MsgPack, JSON, etc. all use already. Pickle was the only one not using these functions, which this PR fixes. So testing this generally seems to be fine. All the other codecs already test decoding with ndarray.
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Thanks for taking a look. |
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Python 3's
pickle.loadsis able to handle anything that conforms to the (new) buffer protocol as long as it is C-contiguous. We go ahead and enforce this on all inputs; raising if that is not possible. On Python 2cPickle.loadsis not as flexible as it requires abytesobject explicitly. This enforces that case as well.TODO:
tox -e py37passes locallytox -e py27passes locallytox -e docspasses locally