[Patches] [ python-Patches-810023 ] Fix for off-by-one bug in urllib.URLopener.retrieve

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Patches item #810023, was opened at 2003-09-21 00:13
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Category: Library (Lib)
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: J. Lewis Muir (jlmuir)
Assigned to: Nobody/Anonymous (nobody)
Summary: Fix for off-by-one bug in urllib.URLopener.retrieve

Initial Comment:
This patch fixes an off-by-one bug in the reporthook part of 

urllib.URLopener.retrieve and adds test cases to verify the 

fix.



The retrieve method reports reading one more block than it 

actually does. Here's an example. The file is empty. I expect 

the initial reporthook call on establishment of the network 

connection but not an additional call since the file is empty 

(no block was read):



>>> import urllib

>>> def reporter(count, blockSize, fileSize):

...     print "c: %i, bs: %i, fs: %i" % (count, blockSize, 

fileSize)

...

>>> srcFile = file("/tmp/empty.txt", "wb")

>>> srcFile.close()

>>> urllib.urlretrieve("file:///tmp/empty.txt", "/tmp/new-

empty.txt", reporter)

c: 0, bs: 8192, fs: 0

c: 1, bs: 8192, fs: 0

('/tmp/new-empty.txt', <mimetools.Message instance at 

0x5a4f58>)

>>>



As a second example, if the file contains 1 byte, the retrieve 

method claims it read 2 blocks when it really only read 1:



>>> srcFile = file("/tmp/empty.txt", "wb")

>>> srcFile.write("x")

>>> srcFile.close()

>>> urllib.urlretrieve("file:///tmp/empty.txt", "/tmp/new-

empty.txt", reporter)

c: 0, bs: 8192, fs: 1

c: 1, bs: 8192, fs: 1

c: 2, bs: 8192, fs: 1

('/tmp/new-empty.txt', <mimetools.Message instance at 

0x5a50d0>)

>>>



This patch also includes some changes to 

test_urllib.urlretrieve_FileTests (where I added the test 

cases) to support creating more than one temporary file and 

making sure any created temporary files get deleted when 

the test case fixture is torn down.



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