def feed(self, data=None):
'''Provide bytes to encrypt (or decrypt), returning any bytes
possible from this or any previous calls to feed.
Call with None or an empty string to flush the mode of
operation and return any final bytes; no further calls to
feed may be made.'''
if self._buffer is None:
raise ValueError('already finished feeder')
# Finalize; process the spare bytes we were keeping
if not data:
result = self._final(self._buffer)
self._buffer = None
return result
self._buffer += to_bufferable(data)
# We keep 16 bytes around so we can determine padding
result = to_bufferable('')
while len(self._buffer) > 16:
can_consume = self._mode._can_consume(len(self._buffer) - 16)
if can_consume == 0: break
result += self._feed(self._buffer[:can_consume])
self._buffer = self._buffer[can_consume:]
return result
def _segment_final_decrypt(self, data):
faux_padding = (chr(0) * (self.segment_bytes -
(len(data) % self.segment_bytes)))
padded = data + to_bufferable(faux_padding)
return self.decrypt(padded)[:len(data)]
def __init__(self, mode, feed, final):
self._mode = mode
self._feed = feed
self._final = final
self._buffer = to_bufferable("")