TypeError when reading from FIFO

[Gribouillis]

It looks like a bug in python(!). If you send a complete reader's side example, I can try it here. Obviously the .buffer member in class codecs.BufferedIncrementalDecoder should never become None. See the class here.

For a more elaborate diagnosis, you could run the following file at the beginning of the reader's program

import codecs
from codecs import IncrementalDecoder

class BufferedIncrementalDecoder(IncrementalDecoder):
    """
    This subclass of IncrementalDecoder can be used as the baseclass for an
    incremental decoder if the decoder must be able to handle incomplete
    byte sequences.
    """
    def __init__(self, errors='strict'):
        IncrementalDecoder.__init__(self, errors)
        # undecoded input that is kept between calls to decode()
        self.buffer = b""

    def _buffer_decode(self, input, errors, final):
        # Overwrite this method in subclasses: It must decode input
        # and return an (output, length consumed) tuple
        raise NotImplementedError

    def decode(self, input, final=False):
        # decode input (taking the buffer into account)
        data = self.buffer + input
        (result, consumed) = self._buffer_decode(data, self.errors, final)
        # keep undecoded input until the next call
        self.buffer = data[consumed:]
        return result

    def reset(self):
        IncrementalDecoder.reset(self)
        self.buffer = b""

    def getstate(self):
        # additional state info is always 0
        return (self.buffer, 0)

    def setstate(self, state):
        # ignore additional state info
        self.buffer = state[0]


# Replace the class in module codecs by our own class
codecs.BufferedIncrementalDecoder = BufferedIncrementalDecoder

Then the codecs module will use your own version of the class. You can now tweak the class' code to detect exactly which bytes are read, when does the buffer becomes None, etc. For example you could turn .buffer into a property and raise an exception as soon as it receives the value None.