[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
Changes by Ezio Melotti ezio.melo...@gmail.com: -- versions: -Python 3.1 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12817 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
Stefan Krah stefan-use...@bytereef.org added the comment: The current interpretation in the PEP-3118 repo is that a request without PyBUF_FORMAT means implicit cast to unsigned bytes. This makes the behavior of PyObject_AsWriteBuffer() correct, so I'm closing this. -- resolution: - invalid stage: patch review - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12817 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
Stefan Krah stefan-use...@bytereef.org added the comment: I've come to think that PyBUF_SIMPLE requests were really intended as a way of casting contiguous buffers with arbitrary formats to one-dimensional buffers of unsigned bytes. At least that is what Numpy does. Then test_multiprocessing would be correct. I've asked the general question on the Numpy mailing list: http://mail.scipy.org/pipermail/numpy-discussion/2011-August/058189.html -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12817 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
Antoine Pitrou pit...@free.fr added the comment: Please also see issue5231. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12817 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
New submission from Stefan Krah stefan-use...@bytereef.org:
Hello,
in my private repo I've changed memoryview's getbufferproc to be PEP-3118
compliant. test_multiprocessing does the equivalent of the following sequence,
which is not allowed by PEP-3118:
import array, io
a = array.array('i', [1,2,3,4,5])
m = memoryview(a)
m.format
'i'
buf = io.BytesIO(bytearray(5))
buf.readinto(m)
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: expected an object with a writable buffer interface
The error occurs in Objects/abstract.c:315:
((*pb-bf_getbuffer)(obj, view, PyBUF_WRITABLE) != 0))
Here, PyObject_AsWriteBuffer() requests a simple writable buffer of unsigned
bytes *without format information* from the memoryview. The memoryview's
getbufferproc is required to return an error:
If format is not explicitly requested then the format must be returned
as NULL (which means B, or unsigned bytes).
But the underlying buffer has format 'i' and not 'B', hence the error.
Antoine, is it correct that io.BytesIO should only be used with bytearray
buffers?
If so, this is a bug in the tests (patch attached).
--
components: Tests
files: test_multiprocessing_use_bytearray.diff
keywords: needs review, patch
messages: 142718
nosy: ncoghlan, pitrou, skrah
priority: normal
severity: normal
stage: patch review
status: open
title: test_multiprocessing: io.BytesIO() requires bytearray buffers
type: behavior
versions: Python 2.7, Python 3.1, Python 3.2, Python 3.3
Added file:
http://bugs.python.org/file22997/test_multiprocessing_use_bytearray.diff
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[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
Stefan Krah stefan-use...@bytereef.org added the comment:
Of course, there is another interpretation:
[PyBUF_FORMAT]
The returned buffer must have true format information if this flag is
provided. This would be used when the consumer is going to be checking for what
'kind' of data is actually stored. An exporter should always be able to provide
this information if requested. If format is not explicitly requested then the
format must be returned as NULL (which means B, or unsigned bytes)
So, the returned buffer may have false format information ('B' vs. 'i'
in this case) if this flag is not provided.
Do you agree with this? I'll then make it explicit in the documentation.
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[issue12817] test_multiprocessing: io.BytesIO() requires bytearray buffers
Antoine Pitrou pit...@free.fr added the comment: Antoine, is it correct that io.BytesIO should only be used with bytearray buffers? BytesIO does a copy of the original object, it does not touch the original buffer. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12817 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
