bpo-27340: Use memoryview in SSLSocket.sendall()

[tiran]

SSLSocket.sendall() now uses memoryview to create slices of data. This fix
support for all bytes-like object. It is also more efficient and avoids
costly copies.

Signed-off-by: Christian Heimes [email protected]

https://bugs.python.org/issue27340

[pitrou]

You should cast the memoryview to a bytes unit, otherwise slicing may work in non-byte units. See e.g. BufferedIOBase.readinto at https://github.com/python/cpython/blob/master/Lib/_pyio.py#L695

[vadmium]

My understanding is that “bytes-like object” is supposed to cover objects without any array dimensions, and arrays of things other than bytes. But naively slicing a memoryview doesn’t work in those cases, and len may not be supported. Test cases:

>>> nonarray = ctypes.c_int()
>>> h.request("POST", "/", body=nonarray)
  File "/usr/lib/python3.5/ssl.py", line 883, in sendall
    amount = len(data)
TypeError: object of type 'c_long' has no len()
>>> nonbyte_array = array.array("I", (0,)) * int(10e6)
>>> # I expect the server may not receive all 40+ MB if a “send” call does a short write

The way I handle this is with memoryview.cast:

with memoryview(byteslike) as view, view.cast("B") as bytes_view:
    ...

E.g. https://github.com/python/cpython/blob/v3.6.2/Lib/_compression.py#L66

[vadmium]

This fixes . . . bytes-like objects.

[tiran]

Thanks @vadmium and @pitrou

I have updated my PR.

[tiran]

2.7 is not affected.

[miss-islington]

🐍🍒⛏🤖 Thanks @tiran for the PR, and @tiran for merging it 🌮🎉.I'm working now to backport this PR to: 3.6.

[miss-islington]

Sorry, @tiran and @tiran, I could not cleanly backport this to 3.6 due to a conflict.
Please backport using cherry_picker on command line.

[bedevere-bot]

GH-3434 is a backport of this pull request to the 3.6 branch.