Split data into a sequence of frames.

def frameify(self, state, data):
        """Split data into a sequence of frames."""

        # Pull in any partially-processed data
        data = state.recv_buf + data

        # Loop over the data
        while data:
            if not state.frame_start:
                try:
                    idx = data.index(self.prefix + self.begin)
                except ValueError:
                    # Can't find the start of a frame...
                    break

                # Advance data to the beginning of the frame (just
                # after the marker)
                data = data[idx + len(self.prefix) + 1:]
                state.frame_start = True

            # Now that data is sitting at the frame start, let's find
            # the frame ending
            try:
                idx = data.index(self.prefix + self.end)
            except ValueError:
                # Can't find the end of the frame...
                break

            # OK, extract the frame and advance the data
            frame = data[:idx]
            data = data[idx + len(self.prefix) + 1:]
            state.frame_start = (self.begin == self.end)

            # Now we need to unstuff the frame
            frame = self.prefix.join(frame.split(self.prefix + self.nop))

            # Yield the frame
            try:
                yield frame
            except FrameSwitch:
                break

        # Put any remaining data back into the buffer
        state.recv_buf = data