New submission from Dan Stromberg <strom...@gmail.com>:
The tarfile module's gettarinfo callable insists on stat'ing the file in
question, preventing one from dynamically generating file content by passing a
file-like object for addfile's fileobj argument.
I believe the attached patch fixes this issue. I generated the patch against
2.7 and tested it with 2.7, but it applies cleanly against 3.1 and "feels
innocuous". I've also included my test code at the bottom of this comment.
Why would you want to do this? Imagine you've stored a file in three smaller
files (perhaps to save the pieces on small external media, or as part of a
deduplication system), with the content divided up into thirds. To
subsequently put this file as a whole into a tar archive, it'd be nice if you
could just create a file-like object to emit the catenation, rather than having
to create a temporary file holding that catenation.
It's occurred to me that this should be done in a more object oriented style,
but that feels a bit inconsistent given that fstat is in the os module, and not
provided as an attribute of a file(-like) object. Comments?
Here's the test code:
#!/usr/local/cpython-2.7/bin/python
import os
import sys
import copy
import array
import stat_tarfile
def my_stat(filename):
class mutable_stat:
pass
readonly_statobj = os.lstat(filename)
mutable_statobj = mutable_stat()
for attribute in dir(readonly_statobj):
if not attribute.startswith('_'):
value = getattr(readonly_statobj, attribute)
setattr(mutable_statobj, attribute, value)
return mutable_statobj
class generate_file_content:
def __init__(self, number):
self._multiplier = 100
self._multipleno = 0
self._number = str(number)
self._buffer = ''
def read(self, length):
while self._multipleno < self._multiplier and len(self._buffer)
< length:
self._buffer += self._number
self._multipleno += 1
if self._buffer == '':
return ''
else:
result = self._buffer[:length]
self._buffer = self._buffer[length:]
return result
def main():
with stat_tarfile.open(fileobj = sys.stdout, mode = "w|") as tar:
for number in xrange(100):
#string = str(number) * 100
fileobj = generate_file_content(number)
statobj = my_stat('/etc/passwd')
statobj.st_size = len(str(number)) * 100
filename = 'file-%d.txt' % number
tarinfo = tar.gettarinfo(filename, statobj = statobj)
tarinfo.uid = 1000
tarinfo.gid = 1000
tarinfo.uname = "dstromberg"
tarinfo.gname = "dstromberg"
tar.addfile(tarinfo, fileobj)
main()
----------
components: Library (Lib)
files: tarfile.diff
keywords: patch
messages: 120822
nosy: strombrg
priority: normal
severity: normal
status: open
title: tarfile requires an actual file on disc; a file-like object is
insufficient
versions: Python 2.7, Python 3.1
Added file: http://bugs.python.org/file19549/tarfile.diff
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue10369>
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