New submission from Alexander Belopolsky:
This problem happens when I unpack a file from a 200+ MB zip archive as follows:
with zipfile.ZipFile(archive) as z:
data = b''
with z.open(filename, 'rU') as f:
for line in f:
data += line
I cannot reduce it to a test case suitable for posting here, but the culprit is
the following code in zipfile.py:
def peek(self, n=1):
"""Returns buffered bytes without advancing the position."""
if n > len(self._readbuffer) - self._offset:
chunk = self.read(n)
self._offset -= len(chunk)
See http://hg.python.org/cpython/file/81f8375e60ce/Lib/zipfile.py#l605
The problem occurs when peek() is called on the boundary of the uncompress
buffer and read() goes through more than one readbuffer. The result is that
self._offset is smaller than len(chunk) leading to a non-sensical negative
self._offset upon return from peek().
This problem does not seem to appear in 3.x since 028e8e0b03e8.
----------
messages: 206779
nosy: belopolsky
priority: normal
severity: normal
status: open
title: zipfile's readline() drops data in universal newline mode
versions: Python 2.7
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<http://bugs.python.org/issue20048>
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