Class _Authenticator

Lib/imaplib.py:1715–1757

Private class to provide en/decoding for base64-based authentication conversation.

class _Authenticator:

    """Private class to provide en/decoding
            for base64-based authentication conversation.
    """

    def __init__(self, mechinst):
        self.mech = mechinst    # Callable object to provide/process data

    def process(self, data):
        ret = self.mech(self.decode(data))
        if ret is None:
            return b'*'     # Abort conversation
        return self.encode(ret)

    def encode(self, inp):
        #
        #  Invoke binascii.b2a_base64 iteratively with
        #  short even length buffers, strip the trailing
        #  line feed from the result and append.  "Even"
        #  means a number that factors to both 6 and 8,
        #  so when it gets to the end of the 8-bit input
        #  there's no partial 6-bit output.
        #
        oup = b''
        if isinstance(inp, str):
            inp = inp.encode('utf-8')
        while inp:
            if len(inp) > 48:
                t = inp[:48]
                inp = inp[48:]
            else:
                t = inp
                inp = b''
            e = binascii.b2a_base64(t)
            if e:
                oup = oup + e[:-1]
        return oup

    def decode(self, inp):
        if not inp:
            return b''
        return binascii.a2b_base64(inp)

Months = ' Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec'.split(' ')
Mon2num = {s.encode():n+1 for n, s in enumerate(Months[1:])}