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# ArFile: a Python representation of ar (as in "man 1 ar") archives.
# Copyright (C) 2007 Stefano Zacchiroli <zack@debian.org>
# Copyright (C) 2007 Filippo Giunchedi <filippo@debian.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
GLOBAL_HEADER = "!<arch>\n"
GLOBAL_HEADER_LENGTH = len(GLOBAL_HEADER)
FILE_HEADER_LENGTH = 60
FILE_MAGIC = "`\n"
class ArError(Exception):
pass
class ArFile(object):
""" Representation of an ar archive, see man 1 ar.
The interface of this class tries to mimick that of the TarFile module in
the standard library.
ArFile objects have the following (read-only) properties:
- members same as getmembers()
"""
def __init__(self, filename=None, mode='r', fileobj=None):
""" Build an ar file representation starting from either a filename or
an existing file object. The only supported mode is 'r' """
self.__members = []
self.__members_dict = {}
self.__fname = filename
self.__fileobj = fileobj
if mode == "r":
self.__index_archive()
pass # TODO write support
def __index_archive(self):
if self.__fname:
fp = open(self.__fname, "rb")
elif self.__fileobj:
fp = self.__fileobj
else:
raise ArError, "Unable to open valid file"
if fp.read(GLOBAL_HEADER_LENGTH) != GLOBAL_HEADER:
raise ArError, "Unable to find global header"
while True:
newmember = ArMember.from_file(fp, self.__fname)
if not newmember:
break
self.__members.append(newmember)
self.__members_dict[newmember.name] = newmember
if newmember.size % 2 == 0: # even, no padding
fp.seek(newmember.size, 1) # skip to next header
else:
fp.seek(newmember.size + 1 , 1) # skip to next header
if self.__fname:
fp.close()
def getmember(self, name):
""" Return the (last occurrence of a) member in the archive whose name
is 'name'. Raise KeyError if no member matches the given name.
Note that in case of name collisions the only way to retrieve all
members matching a given name is to use getmembers. """
return self.__members_dict[name]
def getmembers(self):
""" Return a list of all members contained in the archive.
The list has the same order of members in the archive and can contain
duplicate members (i.e. members with the same name) if they are
duplicate in the archive itself. """
return self.__members
members = property(getmembers)
def getnames(self):
""" Return a list of all member names in the archive. """
return map(lambda f: f.name, self.__members)
def extractall():
""" Not (yet) implemented. """
raise NotImpelementedError # TODO
def extract(self, member, path):
""" Not (yet) implemented. """
raise NotImpelementedError # TODO
def extractfile(self, member):
""" Return a file object corresponding to the requested member. A member
can be specified either as a string (its name) or as a ArMember
instance. """
for m in self.__members:
if isinstance(member, ArMember) and m.name == member.name:
return m
elif member == m.name:
return m
else:
return None
# container emulation
def __iter__(self):
""" Iterate over the members of the present ar archive. """
return iter(self.__members)
def __getitem__(self, name):
""" Same as .getmember(name). """
return self.getmember(name)
class ArMember(object):
""" Member of an ar archive.
Implements most of a file object interface: read, readline, next,
readlines, seek, tell, close.
ArMember objects have the following (read-only) properties:
- name member name in an ar archive
- mtime modification time
- owner owner user
- group owner group
- fmode file permissions
- size size in bytes
- fname file name"""
def __init__(self):
self.__name = None # member name (i.e. filename) in the archive
self.__mtime = None # last modification time
self.__owner = None # owner user
self.__group = None # owner group
self.__fmode = None # permissions
self.__size = None # member size in bytes
self.__fname = None # file name associated with this member
self.__fp = None # file pointer
self.__offset = None # start-of-data offset
self.__end = None # end-of-data offset
def from_file(fp, fname):
"""fp is an open File object positioned on a valid file header inside
an ar archive. Return a new ArMember on success, None otherwise. """
buf = fp.read(FILE_HEADER_LENGTH)
if not buf:
return None
# sanity checks
if len(buf) < FILE_HEADER_LENGTH:
raise IOError, "Incorrect header length"
if buf[58:60] != FILE_MAGIC:
raise IOError, "Incorrect file magic"
# http://en.wikipedia.org/wiki/Ar_(Unix)
#from to Name Format
#0 15 File name ASCII
#16 27 File modification date Decimal
#28 33 Owner ID Decimal
#34 39 Group ID Decimal
#40 47 File mode Octal
#48 57 File size in bytes Decimal
#58 59 File magic \140\012
# XXX struct.unpack can be used as well here
f = ArMember()
f.__name = buf[0:16].split("/")[0].strip()
f.__mtime = int(buf[16:28])
f.__owner = int(buf[28:34])
f.__group = int(buf[34:40])
f.__fmode = buf[40:48] # XXX octal value
f.__size = int(buf[48:58])
f.__fname = fname
f.__offset = fp.tell() # start-of-data
f.__end = f.__offset + f.__size
return f
from_file = staticmethod(from_file)
# file interface
# XXX this is not a sequence like file objects
def read(self, size=0):
if self.__fp is None:
self.__fp = open(self.__fname, "r")
self.__fp.seek(self.__offset)
cur = self.__fp.tell()
if size > 0 and size <= self.__end - cur: # there's room
return self.__fp.read(size)
if cur >= self.__end or cur < self.__offset:
return ''
return self.__fp.read(self.__end - cur)
def readline(self, size=None):
if self.__fp is None:
self.__fp = open(self.__fname, "r")
self.__fp.seek(self.__offset)
if size is not None:
buf = self.__fp.readline(size)
if self.__fp.tell() > self.__end:
return ''
return buf
buf = self.__fp.readline()
if self.__fp.tell() > self.__end:
return ''
else:
return buf
def readlines(self, sizehint=0):
if self.__fp is None:
self.__fp = open(self.__fname, "r")
self.__fp.seek(self.__offset)
buf = None
lines = []
while True:
buf = self.readline()
if not buf:
break
lines.append(buf)
return lines
def seek(self, offset, whence=0):
if self.__fp is None:
self.__fp = open(self.__fname, "r")
self.__fp.seek(self.__offset)
if self.__fp.tell() < self.__offset:
self.__fp.seek(self.__offset)
if whence < 2 and offset + self.__fp.tell() < self.__offset:
raise IOError, "Can't seek at %d" % offset
if whence == 1:
self.__fp.seek(offset, 1)
elif whence == 0:
self.__fp.seek(self.__offset + offset, 0)
elif whence == 2:
self.__fp.seek(self.__end + offset, 0)
def tell(self):
if self.__fp is None:
self.__fp = open(self.__fname, "r")
self.__fp.seek(self.__offset)
cur = self.__fp.tell()
if cur < self.__offset:
return 0L
else:
return cur - self.__offset
def close(self):
if self.__fp is not None:
self.__fp.close()
def next(self):
return self.readline()
def __iter__(self):
def nextline():
line = self.readline()
if line:
yield line
return iter(nextline())
name = property(lambda self: self.__name)
mtime = property(lambda self: self.__mtime)
owner = property(lambda self: self.__owner)
group = property(lambda self: self.__group)
fmode = property(lambda self: self.__fmode)
size = property(lambda self: self.__size)
fname = property(lambda self: self.__fname)
if __name__ == '__main__':
# test
# ar r test.ar <file1> <file2> .. <fileN>
a = ArFile("test.ar")
print "\n".join(a.getnames())
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