import scipy

def remove_zeroes_in_msg_stream(stream, start_of_msg, end_of_msg):
  filtered = []
  num_msg = 0
  state="ZEROES"
  for b in stream:
    if state == "ZEROES":
      if b != 0:
        if b != start_of_msg: # this should not happen
          print "Error!", b
        else:
          state = "DATA"
          num_msg += 1
          msg_len = 1
    elif state == "DATA":
      if b == end_of_msg:
        state = "TAIL"
    elif state == "TAIL":
      if b == 0:
        state = "ZEROES"
    if state != "ZEROES":
      filtered.append(b)
      msg_len += 1
  return filtered, num_msg, msg_len

stream = scipy.fromfile(open("test"), dtype=scipy.uint8)
cnt_som = 0
cnt_eom = 0
som = 170
eom = 23
state = "ZEROES"
num_msg = 0
signaling_len = 8

for bb in stream:
  if state == "ZEROES":
    if bb != 0:
      if bb != som: # this should not happen
        raise ValueError("Beginning of message is not som.")
      else:
        state = "PREAMBLE"
        num_msg += 1
        preamble_len = 1
  elif state == "PREAMBLE":
    if bb != som:
      if preamble_len != signaling_len and preamble_len > 2:
        raise ValueError("Wrong preamble len of " + str(preamble_len) + "." \
                + ". Current byte " + str(bb) + ". Current message " + str(num_msg) + ".")
      state = "DATA"
      data_len = 1
    else:
      preamble_len += 1
  elif state == "DATA":
    if bb == eom:
      state = "TAIL"
      tail_len = 1
    else:
      data_len += 1
  elif state == "TAIL":
    if bb != eom:
      if tail_len != signaling_len and tail_len > 2:
        raise ValueError("Wrong tail len of " + str(tail_len) + ". Current byte " + str(bb) + ". Current message " + str(num_msg) + ".")
      elif bb == som:
        state = "PREAMBLE"
        preamble_len = 1
        num_msg += 1
      elif bb == 0:
        state = "ZEROES"
    else:
      tail_len += 1
  if state != "ZEROES":
    print bb

print "Number of messages:", num_msg