class decompressobj(object):
def __init__(self, wbits=MAX_WBITS):
# Jython only uses wbits to determine to skip the header if it's negative;
# but apparently there are some tests around this that we do some bogus
# param checking
if abs(wbits) < 8:
raise ValueError, "Invalid initialization option"
if abs(wbits) > 16: # NOTE apparently this also implies being negative in CPython/zlib
wbits = -1
self.inflater = Inflater(wbits < 0)
self._ended = False
self.unused_data = ""
self.unconsumed_tail = ""
self.gzip = wbits < 0
self.gzip_header_skipped = False
self._crc32 = CRC32()
def decompress(self, string, max_length=0):
if self._ended:
raise error("decompressobj may not be used after flush()")
# unused_data is always "" until inflation is finished; then it is
# the unused bytes of the input;
# unconsumed_tail is whatever input was not used because max_length
# was exceeded before inflation finished.
# Thus, at most one of {unused_data, unconsumed_tail} may be non-empty.
self.unconsumed_tail = ""
if not self.inflater.finished() and not (self.gzip and not self.gzip_header_skipped):
self.unused_data = ""
if max_length < 0:
raise ValueError("max_length must be a positive integer")
# Suppress gzip header if present and wbits < 0
if self.gzip and not self.gzip_header_skipped:
string = self.unused_data + string
self.unused_data = ""
try:
string = _skip_gzip_header(string)
except IndexError:
# need more input!
self.unused_data = string
return ""
self.gzip_header_skipped = True
string = _to_input(string)
self.inflater.setInput(string)
inflated = _get_inflate_data(self.inflater, max_length)
self._crc32.update(inflated)
r = self.inflater.getRemaining()
if r:
if self.gzip and self.inflater.finished() and r == 8:
# Consume tail, check inflate size, and crc32
crc,isize = struct.unpack_from("<LL", string[-r:])
mysize = self.inflater.getBytesWritten() & _MASK32
mycrc = self._crc32.getValue() & _MASK32
if mysize != isize:
raise error('Error -3 while decompressing data: incorrect length check')
if mycrc != crc:
raise error("Error -3 while decompressing data: incorrect data check")
elif max_length and not self.inflater.finished():
self.unconsumed_tail = string[-r:]
else:
self.unused_data += string[-r:]
return inflated
def flush(self, length=None):
if self._ended:
raise error("decompressobj may not be used after flush()")
if length is None:
length = 0
elif length <= 0:
raise ValueError('length must be greater than zero')
last = _get_inflate_data(self.inflater, length)
self.inflater.end()
return last
