[ python-Bugs-1478529 ] size limit exceeded for read() from network drive

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Bugs item #1478529, was opened at 2006-04-28 12:46
Message generated for change (Comment added) made by tim_one
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Category: Windows
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Mark Sheppard (markshep)
Assigned to: Nobody/Anonymous (nobody)
Summary: size limit exceeded for read() from network drive

Initial Comment:
If you've got a network share mounted as a local drive
then Windows has a limit of 67,076,095 (0x03ff7fff)
bytes for a read from an open file on that drive.

Running the python read() method on an open file larger
than this size throws an "IOError: [Errno 22] Invalid
argument" exception.

A fix would be for python to internally use multiple
reads so as to not exceed this limit.


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>Comment By: Tim Peters (tim_one)
Date: 2006-04-30 12:23

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Martin, here's an MS article seemingly related to this:

http://support.microsoft.com/default.aspx?scid=kb;en-us;899149

However, it's about writing to a file on a network drive,
not reading from it.  It says that opening the file in 'w+b'
mode, instead of 'wb' mode, is a workaround.

I couldn't find anything documenting the same kind of
problem for reading.

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Comment By: Martin v. Löwis (loewis)
Date: 2006-04-30 06:10

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What version of Windows are you using? Do you know of any
documentation of this limit? (without actually testing, I
find it hard to believe that this limit exists in Windows)

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Comment By: Georg Brandl (gbrandl)
Date: 2006-04-29 09:23

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How can it be determined whether exactly this restriction
caused the "invalid argument" error? If it can't, there's
nothing that can be done -- restricting all reads just
because of a Windows limitation doesn't seem right.

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