def _parse_cffile(self, offset):
""" Parse a CFFILE entry """
fmt = '<I' # uncompressed size
fmt += 'I' # uncompressed offset of this file in the folder
fmt += 'H' # index into the CFFOLDER area
fmt += 'H' # date
fmt += 'H' # time
fmt += 'H' # attribs
try:
vals = struct.unpack_from(fmt, self._buf_file, offset)
except struct.error as e:
raise CorruptionError(str(e))
# debugging
if os.getenv('PYTHON_CABARCHIVE_DEBUG'):
print "CFFILE", vals
# parse filename
offset += struct.calcsize(fmt)
filename = ''
for i in range(0, 255):
filename_c = self._buf_file[offset + i]
if filename_c == b'\0':
break
filename += filename_c
# add file
f = CabFile(filename)
f._date_decode(vals[3])
f._time_decode(vals[4])
f._attr_decode(vals[5])
f.contents = self._folder_data[vals[2]][vals[1]:vals[1] + vals[0]]
if len(f.contents) != vals[0]:
raise CorruptionError("Corruption inside archive, %s is size %i but "
"expected size %i" % (filename, len(f.contents), vals[0]))
self.files.append(f)
# return offset to next entry
return 16 + len(filename) + 1
def parse(self, buf):
""" Parse .cab data """
# we've got an external binary to help us
if self._decompressor:
import tempfile
import subprocess
import shutil
# write to temp file
src = tempfile.NamedTemporaryFile(mode='wb',
prefix='cabarchive_',
suffix=".cab",
dir=self._tmpdir,
delete=True)
src.write(buf)
src.flush()
# decompress to a temp directory
dest_fn = tempfile.mkdtemp(prefix='cabarchive_', dir=self._tmpdir)
argv = [self._decompressor,
'--quiet',
'--directory',
dest_fn,
src.name]
ps = subprocess.Popen(argv, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
if ps.wait() != 0:
raise CorruptionError("Failed to extract: %s" % ps.stderr.read())
# add all the fake CFFILE objects
for fn in _listdir_recurse(dest_fn):
cff = CabFile(os.path.basename(fn))
cff.contents = open(fn, 'rb').read()
self.add_file(cff)
shutil.rmtree(dest_fn)
src.close()
return
# slurp the whole buffer at once
self._buf_file = buf
# read the file header
fmt = '<4s' # signature
fmt += 'xxxx' # reserved1
fmt += 'I' # size
fmt += 'xxxx' # reserved2
fmt += 'I' # offset to CFFILE
fmt += 'xxxx' # reserved3
fmt += 'BB' # version minor, major
fmt += 'H' # no of CFFOLDERs
fmt += 'H' # no of CFFILEs
fmt += 'H' # flags
fmt += 'H' # setID
fmt += 'H' # cnt of cabs in set
# fmt += 'H' # reserved cab size
# fmt += 'B' # reserved folder size
# fmt += 'B' # reserved block size
# fmt += 'B' # per-cabinet reserved area
try:
vals = struct.unpack_from(fmt, self._buf_file, 0)
except struct.error as e:
raise CorruptionError(str(e))
# debugging
if os.getenv('PYTHON_CABARCHIVE_DEBUG'):
print "CFHEADER", vals
# check magic bytes
if vals[0] != b'MSCF':
raise NotSupportedError('Data is not application/vnd.ms-cab-compressed')
# check size matches
if vals[1] != len(self._buf_file):
raise CorruptionError('Cab file internal size does not match data')
# check version
if vals[4] != 1 or vals[3] != 3:
raise NotSupportedError('Version %i.%i not supported' % (vals[4], vals[3]))
# chained cabs not supported
if vals[9] != 0:
raise NotSupportedError('Chained cab file not supported')
# verify we actually have data
nr_files = vals[6]
if nr_files == 0:
raise CorruptionError('The cab file is empty')
# verify we got complete data
off_cffile = vals[2]
if off_cffile > len(self._buf_file):
raise CorruptionError('Cab file corrupt')
# chained cabs not supported
if vals[7] != 0:
raise CorruptionError('Expected header flags to be cleared')
# read this so we can do round-trip
self.set_id = vals[8]
# we don't support compressed folders in multi-folder archives
if vals[5] > 1:
self._is_multi_folder = True
# parse CFFOLDER
offset = struct.calcsize(fmt)
for i in range(vals[5]):
self._parse_cffolder(i, offset)
offset += struct.calcsize(FMT_CFFOLDER)
# parse CFFILEs
for i in range(0, nr_files):
off_cffile += self._parse_cffile(off_cffile)
