[issue10045] poor cStringIO.StringO seek performance
New submission from Patrick Strawderman : cStringIO.StringO's seek method has O(n) characteristics in certain, albeit pathological, cases, while the pure Python implementation and cStringIO.StringI's seek methods both execute in constant time in all cases. When the file offset is set n bytes beyond the end of actual data, the gap is filled in with n bytes in cStringIO.StringO's seek method. however, POSIX states that reads of data in the gap will return null bytes only if a subsequent write has taken place, so filling in the gap is not required at the time of the seek. This patch for 2.7 corrects the behavior by unifying StringO and StringI's seek methods, and moving the writing of null bytes to StringO's write method. There may be a more elegant way to write this, I don't know. I believe this issue affects Python 3 as well, though I have yet to test it. NOTE: Perhaps this seems like an extreme edge case not worthy of a fix, but this actually caused problems for us when parsing images with malformed EXIF data; a web request for uploading such a photo was taking on the order of 15 minutes. When we stopped using cStringIO.StringO, it took seconds. -- files: cStringIO.diff keywords: patch messages: 118123 nosy: boogenhagn priority: normal severity: normal status: open title: poor cStringIO.StringO seek performance versions: Python 2.6, Python 2.7, Python 3.1, Python 3.2, Python 3.3 Added file: http://bugs.python.org/file19150/cStringIO.diff ___ Python tracker <http://bugs.python.org/issue10045> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue10045] poor cStringIO.StringO seek performance
Changes by Patrick Strawderman : -- components: +None type: -> performance ___ Python tracker <http://bugs.python.org/issue10045> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue10045] poor cStringIO.StringO seek performance
Changes by Patrick Strawderman : -- components: -None ___ Python tracker <http://bugs.python.org/issue10045> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue10045] poor cStringIO.StringO seek performance
Patrick Strawderman added the comment: The second sentence should have said "the gap is filled in with n null bytes" -- ___ Python tracker <http://bugs.python.org/issue10045> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue10045] poor cStringIO.StringO seek performance
Patrick Strawderman added the comment: Fair enough, but there is a great deal of existing code that already uses cStringIO. -- ___ Python tracker <http://bugs.python.org/issue10045> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6553] cPickle "binunicode" segmentation fault
New submission from Patrick Strawderman :
When reading from a file-like object (like StringIO), cPickle uses the
read_other function, which doesn't check that the number of bytes
requested is the actual number of bytes read (like the read_cStringIO
function does).
Functions like load_binunicode falsely assume that the number of bytes
specified after the BINUNICODE instruction are the actual number of
bytes read. This can eventually lead to a segmentation fault, as
demonstrated in the following example:
import cPickle, StringIO
cPickle.Unpickler(StringIO.StringIO("X''.")).load()
I have tested and reproduced this on Python 2.4.6 (OS X 32-bit), 2.5.1
(OS X 32-bit), and 2.6.2 (Linux 64-bit).
I have not tested Python 3.x, but I believe this problem may be akin to
the one in issue4298.
--
messages: 90847
nosy: boogenhagn
severity: normal
status: open
title: cPickle "binunicode" segmentation fault
versions: Python 2.4, Python 2.5, Python 2.6
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[issue9327] doctest DocFileCase setUp/tearDown asymmetry
New submission from Patrick Strawderman : doctest.DocFileTest inserts the test's path into the globs as "__file__", but doctest.DocTestCase's tearDown method simply calls globs.clear(), so that subsequent runs of the test case will not receive the same initial globals. This means that doctests referencing __file__ cannot be run repeatedly without using a custom setUp that restores __file__. I think most would expect symmetry between setUp and tearDown, and in fact zope.testrunner operates with this false assumption when run with the "-N" option to repeat a test N times. -- components: Library (Lib) messages: 27 nosy: boogenhagn, fdrake priority: normal severity: normal status: open title: doctest DocFileCase setUp/tearDown asymmetry type: behavior versions: Python 2.6, Python 2.7, Python 3.1, Python 3.2, Python 3.3 ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9327] doctest DocFileCase setUp/tearDown asymmetry
Changes by Patrick Strawderman : Added file: http://bugs.python.org/file18114/doctestbug.py ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9327] doctest DocFileCase setUp/tearDown asymmetry
Changes by Patrick Strawderman : Added file: http://bugs.python.org/file18115/doctestbugpy3.py ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9327] doctest DocFileCase setUp/tearDown asymmetry
Changes by Patrick Strawderman : -- versions: -Python 3.3 ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9327] doctest DocFileCase setUp/tearDown asymmetry
Changes by Patrick Strawderman : Removed file: http://bugs.python.org/file18114/doctestbug.py ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9327] doctest DocFileCase setUp/tearDown asymmetry
Changes by Patrick Strawderman : Removed file: http://bugs.python.org/file18115/doctestbugpy3.py ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9327] doctest DocFileCase setUp/tearDown asymmetry
Changes by Patrick Strawderman : Added file: http://bugs.python.org/file18116/doctestbug.py ___ Python tracker <http://bugs.python.org/issue9327> ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
