[New-bugs-announce] [issue10369] tarfile requires an actual file on disc; a file-like object is insufficient
report at bugs.python.org
Tue Nov 9 00:42:07 CET 2010
New submission from Dan Stromberg <strombrg at 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:
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)
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 == '':
result = self._buffer[:length]
self._buffer = self._buffer[length:]
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"
components: Library (Lib)
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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