On Wed, Mar 04, 2009 at 03:15:14PM -0700, Novell Forge SVN wrote:

Author: Marcus_H Date: 2009-03-04 15:15:11 -0700 (Wed, 04 Mar 2009) New Revision: 6699

Added: trunk/buildservice/src/clientlib/python/osc/osc/util/ trunk/buildservice/src/clientlib/python/osc/osc/util/__init__.py trunk/buildservice/src/clientlib/python/osc/osc/util/ar.py Log: - added ar module: this can be used to read ar archives. This will be used later to extract files from a debian package which uses this format. Currently we only support the GNU format (note: maybe something is still missing but it's sufficient for our needs)

One step further towards injection of rpm^Wdeb requires injection? Nice :-) (Marcus and I discussed offline a bit, whether this should become a Python module in its own. Maybe it still can become one later. Maybe my (comparatively stupid) cpio bits could accompany this...)

Added: trunk/buildservice/src/clientlib/python/osc/osc/util/ar.py =================================================================== --- trunk/buildservice/src/clientlib/python/osc/osc/util/ar.py (rev 0) +++ trunk/buildservice/src/clientlib/python/osc/osc/util/ar.py 2009-03-04 22:15:11 UTC (rev 6699) @@ -0,0 +1,154 @@

I see one thing missing here, or rather I don't see it: A copyright and license header. I guess one should be present, in particular because this module looks a little bit detached (in the sense of independent) from the rest of the code.

+import os +import re +import sys +import StringIO +import stat + +class ArError(Exception): + """Base class for all ar related errors""" + def __init__(self, fn, msg): + Exception.__init__(self) + self.file = fn + self.msg = msg + + def __str__(self): + return 'ar error: %s' % self.msg + +class ArHdr(): + """Represents an ar header entry""" + def __init__(self, fn, date, uid, gid, mode, size, fmag, off): + self.file = fn.strip() + self.date = date.strip() + self.uid = uid.strip() + self.gid = gid.strip() + self.mode = stat.S_IMODE(int(mode, 8)) + self.size = int(size) + self.fmag = fmag + # data section starts at off and ends at off + size + self.dataoff = int(off) + + def __str__(self): + return '%16s %d' % (self.file, self.size) + +class ArFile(StringIO.StringIO): + """Represents a file which resides in the archive""" + def __init__(self, fn, uid, gid, mode, buf): + StringIO.StringIO.__init__(self, buf) + self.name = fn + self.uid = uid + self.gid = gid + self.mode = mode + + def saveTo(self, dir = None): + if not dir: + dir = os.getcwd() + fn = os.path.join(dir, self.name) + f = open(fn, 'wb') + f.write(self.getvalue())

Ah, so this can actually save a part from the archive to disk?

+ f.close() + os.chmod(fn, self.mode) + uid = self.uid + if uid != os.geteuid() or os.geteuid() != 0: + uid = -1 + gid = self.gid + if not gid in os.getgroups() or os.getegid() != 0: + gid = -1 + os.chown(fn, uid, gid) + +class Ar(): + """ + Represents an ar archive (only GNU format is supported). + Readonly access. + """ + hdr_len = 60 + hdr_pat = re.compile('^(.{16})(.{12})(.{6})(.{6})(.{8})(.{10})(.{2})', re.DOTALL)

Interesting approach - I would have used struct.unpack for this, I guess.

+ + def __init__(self, fn): + self.filename = fn + self.hdrs = [] + self.ext_fnhdr = None + # file object: will be closed in __del__() + self.__file = None + + def __del__(self): + if self.__file: + self.__file.close() + + def _appendHdr(self, hdr): + # GNU uses an internal '//' file to store very long filenames + if hdr.file.startswith('//'): + self.ext_fnhdr = hdr + else: + self.hdrs.append(hdr) + + def _fixupFilenames(self): + """ + support the GNU approach for very long filenames: + every filename which exceeds 16 bytes is stored in the data section of a special file ('//') + and the filename in the header of this long file specifies the offset in the special file's + data section. The end of such a filename is indicated with a trailing '/'. + Another special file is the '/' which contains the symbol lookup table. + """ + for h in self.hdrs: + if h.file == '/': + continue + # remove slashes which are appended by ar + h.file = h.file.rstrip('/') + if not h.file.startswith('/'): + continue + # handle long filename + off = int(h.file[1:len(h.file)]) + start = self.ext_fnhdr.dataoff + off + self.__file.seek(start, os.SEEK_SET) + # XXX: is it safe to read all the data in one chunk? I assume the '//' data section + # won't be too large + data = self.__file.read(self.ext_fnhdr.size) + end = data.find('/') + if end != -1: + h.file = data[0:end] + else: + raise ArError('//', 'invalid data section - trailing slash (off: %d)' % start) + + + def read(self): + """reads in the archive. It tries to use mmap due to performance reasons (in case of large files)""" + if not self.__file: + import mmap + self.__file = open(self.filename, 'rb') + try: + self.__file = mmap.mmap(self.__file.fileno(), 0, prot=mmap.PROT_READ) + except EnvironmentError, e: + if e.errno == 19: + print >>sys.stderr, 'cannot use mmap to read the file, falling back to the default io'

Wise... we had this before...

+ else: + raise e + else: + self.__file.seek(0, os.SEEK_SET) + data = self.__file.read(7) + if data != '!<arch>': + raise ArError(self.filename, 'no ar archive') + pos = 8 + while (len(data) != 0): + self.__file.seek(pos, os.SEEK_SET) + data = self.__file.read(self.hdr_len) + if not data: + break + pos += self.hdr_len + m = self.hdr_pat.search(data) + if not m: + raise ArError(self.filename, 'unexpected hdr entry') + args = m.groups() + (pos, ) + hdr = ArHdr(*args) + self._appendHdr(hdr) + # data blocks are 2 bytes aligned - if they end on an odd + # offset ARFMAG[0] will be used for padding (according to the current binutils code) + pos += hdr.size + (hdr.size & 1) + self._fixupFilenames() + + def get_file(self, fn): + for h in self.hdrs: + if h.file == fn: + self.__file.seek(h.dataoff, os.SEEK_SET) + return ArFile(h.file, h.uid, h.gid, h.mode, + self.__file.read(h.size)) + return None

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