bgneal@65: M209 Class
bgneal@65: ==========
bgneal@65: 
bgneal@65: Naturally, the ``m209`` library includes a class that simulates a M-209
bgneal@65: converter. The :class:`~m209.converter.M209` class allows you to experiment
bgneal@65: with all moving parts of an M-209, including encrypting and decrypting
bgneal@69: messages. Keep in mind there is a higher level class,
bgneal@69: :class:`~m209.procedure.StdProcedure`, that encapsulates all the steps of the
bgneal@69: standard encrypting and decrypting operations, including generating indicators
bgneal@69: and placing or removing them from messages. However if you need lower-level
bgneal@69: access or you are inventing your own procedures, you would use the M209 class
bgneal@69: directly.
bgneal@65: 
bgneal@65: .. class:: m209.converter.M209([lugs=None[, pin_list=None]])
bgneal@65: 
bgneal@65:    The ``M209`` class takes the following optional arguments.
bgneal@65: 
bgneal@65:   :param lugs: either a lug settings list or string as per :meth:`set_drum_lugs`
bgneal@65:   :param pin_list: a list of six strings each formatted as per :ref:`pin-settings`
bgneal@65: 
bgneal@67: ``M209`` objects have the following attributes.
bgneal@67: 
bgneal@67:    .. attribute:: letter_count
bgneal@67: 
bgneal@67:       This attribute represents the *letter counter* functionality. It is an
bgneal@67:       integer that is incremented after every letter is encrypted or decrypted.
bgneal@67:       It may be set to any integer value or examined at any time.
bgneal@67: 
bgneal@65: ``M209`` objects support the following methods.
bgneal@65: 
bgneal@65:    .. method:: set_pins(n, effective_pins)
bgneal@65: 
bgneal@65:       Sets the pin settings on the specified key wheel ``n``.
bgneal@65: 
bgneal@65:       :param n: an integer between 0-5, inclusive. Key wheel 0 is the 
bgneal@65:          left-most wheel and wheel 5 is the right-most.
bgneal@65: 
bgneal@65:       :param effective_pins: an iterable of letters whose pins are slid to
bgneal@65:         the "effective" position (to the right). See :ref:`pin-settings`.
bgneal@65: 
bgneal@65:    .. method:: set_all_pins(pin_list)
bgneal@65: 
bgneal@65:       Sets all key wheel pins according to the supplied pin list.
bgneal@65: 
bgneal@65:       :param pin_list: must either be ``None`` or a 6-element list of strings
bgneal@65:          where each string element is as described in :ref:`pin-settings`.
bgneal@65:          If ``None``, all pins in all key wheels are moved to the ineffective position.
bgneal@65: 
bgneal@65:    .. method:: set_drum_lugs(lug_list)
bgneal@65: 
bgneal@65:       Sets the drum lugs according to the given ``lug_list`` parameter.
bgneal@65: 
bgneal@65:       If ``lug_list`` is ``None`` or empty, all lugs will be placed in neutral
bgneal@65:       positions.
bgneal@65: 
bgneal@65:       Otherwise, the ``lug_list`` can either be a list or a string.
bgneal@65: 
bgneal@65:       If ``lug_list`` is passed a list, it must be a list of 1 or 2-tuple integers,
bgneal@65:       where each integer is between 0-5, inclusive, and represents a 0-based
bgneal@65:       key wheel position. The list can not be longer than 27 items. Only lug
bgneal@65:       bars with lugs in non-neutral positions need be listed. Lug bars with one
bgneal@65:       lug in a non-neutral position are represented by a 1-tuple. Bars with
bgneal@65:       2 non-netural lugs are represented as a 2-tuple.
bgneal@65: 
bgneal@65:       If ``lug_list`` is passed as a string, it is assumed to be in key list
bgneal@65:       format as described in :ref:`lug-settings`.
bgneal@65: 
bgneal@65:       Example::
bgneal@65: 
bgneal@65:          m = M209()
bgneal@65:          m.set_drum_lugs('1-0 2-0*2 0-3 0-5*3 0-6 2-4 3-6')
bgneal@65: 
bgneal@65:          # or equivalently
bgneal@65:          m.set_drum_lugs([(0, ), (1, ), (1, ), (2, ), (4, ), (4, ), (4, ), (5, ), (1, 3), (2, 5)])
bgneal@65: 
bgneal@65: 
bgneal@65:    .. method:: set_key_wheel(n, c)
bgneal@65: 
bgneal@65:       Set key wheel ``n`` to the letter ``c``.
bgneal@65: 
bgneal@65:       :param n: an integer between 0-5 where key wheel 0 is the leftmost key wheel,
bgneal@65:          and 5 is the rightmost
bgneal@65:       :param c: a 1-letter string valid for key wheel ``n``
bgneal@65:       :raises KeyWheelError: if ``c`` is not valid for wheel ``n``
bgneal@65: 
bgneal@65:    .. method:: set_key_wheels(s)
bgneal@65: 
bgneal@65:       Set the key wheels from left to right to the six letter string ``s``.
bgneal@65: 
bgneal@65:       :raises KeyWheelError: if any letter in ``s`` is not valid for the corresponding key wheel
bgneal@65: 
bgneal@65:    .. method:: set_random_key_wheels()
bgneal@65: 
bgneal@65:       Sets the six key wheels to random letters.
bgneal@65: 
bgneal@65:       :returns: a string of length six representing the new key wheel settings
bgneal@65: 
bgneal@65:    .. method:: get_settings()
bgneal@65: 
bgneal@65:       Returns the current key settings.
bgneal@65: 
bgneal@65:       :returns: a named tuple of ``(lugs, pin_list)`` representing the current
bgneal@65:          key settings. ``lugs`` will be in string format.
bgneal@65: 
bgneal@65:    .. method:: encrypt(plaintext[, group=True[, spaces=True]])
bgneal@65: 
bgneal@65:       Performs an encrypt operation on the given plaintext and returns the
bgneal@65:       encrypted ciphertext as a string.
bgneal@65: 
bgneal@65:       :param plaintext: the text string to encrypt
bgneal@65:       :param group: if ``True``, the ciphertext string will be grouped into 5-letter
bgneal@65:          groups, separated by spaces
bgneal@65:       :param spaces: if ``True``, space characters in the input plaintext will
bgneal@65:          automatically be treated as ``Z`` characters. Otherwise spaces in the
bgneal@65:          plaintext will raise an ``M209Error``.
bgneal@65:       :returns: the ciphertext as a string
bgneal@65: 
bgneal@65:    .. method:: decrypt(ciphertext[, spaces=True[, z_sub=True]])
bgneal@65: 
bgneal@65:       Performs a decrypt operation on the given ciphertext and returns the
bgneal@65:       decrypted plaintext as a string.
bgneal@65: 
bgneal@65:       :param ciphertext: the text string to decyrpt
bgneal@65:       :param spaces: if ``True``, spaces will be allowed in the input ciphertext and
bgneal@65:          ignored. Otherwise space characters will raise an ``M209Error``.
bgneal@65:          This is useful if the input ciphertext is in 5-letter groups, separated
bgneal@65:          by spaces.
bgneal@65:       :param z_sub: if ``True``, ``Z`` characters in the output plaintext will be
bgneal@65:          replaced by space characters, just like an actual M-209.
bgneal@65:       :returns: the plaintext as a string
bgneal@65: 
bgneal@65: Example:
bgneal@65: 
bgneal@65: >>> from m209.converter import M209
bgneal@65: >>> m = M209()
bgneal@65: >>> m.set_drum_lugs('1-0 2-0*2 0-3 0-5*3 0-6 2-4 3-6')
bgneal@65: >>> pin_list = [
bgneal@65: ...     'FGIKOPRSUVWYZ',
bgneal@65: ...     'DFGKLMOTUY',
bgneal@65: ...     'ADEFGIORTUVX',
bgneal@65: ...     'ACFGHILMRSU',
bgneal@65: ...     'BCDEFJKLPS',
bgneal@65: ...     'EFGHIJLMNP'
bgneal@65: ... ]
bgneal@65: >>> m.set_all_pins(pin_list)
bgneal@65: >>> m.set_key_wheels('FFEGJP')
bgneal@65: >>> ct = m.encrypt('THE PIZZA HAS ARRIVED')
bgneal@65: >>> ct
bgneal@65: 'QBCHU WCCDI YFNCH LOZJY G'
bgneal@65: >>> m.set_key_wheels('FFEGJP')
bgneal@65: >>> pt = m.decrypt(ct)
bgneal@65: >>> pt
bgneal@65: 'THE PI  A HAS ARRIVED'