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Documented the M209's letter_count attribute.
author Brian Neal <bgneal@gmail.com>
date Sat, 20 Jul 2013 19:13:41 -0500
parents 256b3f3e35e9
children 2173ac4c2d9b
rev   line source
bgneal@65 1 M209 Class
bgneal@65 2 ==========
bgneal@65 3
bgneal@65 4 Naturally, the ``m209`` library includes a class that simulates a M-209
bgneal@65 5 converter. The :class:`~m209.converter.M209` class allows you to experiment
bgneal@65 6 with all moving parts of an M-209, including encrypting and decrypting
bgneal@65 7 messages. Keep in mind there is a higher level class, StdProcedure, that
bgneal@65 8 encapsulates all the steps of the standard encrypting and decrypting
bgneal@65 9 operations, including generating indicators and placing or removing them from
bgneal@65 10 messages. However if you need lower-level access or you are inventing your own
bgneal@65 11 procedures, you would use the M209 class directly.
bgneal@65 12
bgneal@65 13 .. class:: m209.converter.M209([lugs=None[, pin_list=None]])
bgneal@65 14
bgneal@65 15 The ``M209`` class takes the following optional arguments.
bgneal@65 16
bgneal@65 17 :param lugs: either a lug settings list or string as per :meth:`set_drum_lugs`
bgneal@65 18 :param pin_list: a list of six strings each formatted as per :ref:`pin-settings`
bgneal@65 19
bgneal@67 20 ``M209`` objects have the following attributes.
bgneal@67 21
bgneal@67 22 .. attribute:: letter_count
bgneal@67 23
bgneal@67 24 This attribute represents the *letter counter* functionality. It is an
bgneal@67 25 integer that is incremented after every letter is encrypted or decrypted.
bgneal@67 26 It may be set to any integer value or examined at any time.
bgneal@67 27
bgneal@65 28 ``M209`` objects support the following methods.
bgneal@65 29
bgneal@65 30 .. method:: set_pins(n, effective_pins)
bgneal@65 31
bgneal@65 32 Sets the pin settings on the specified key wheel ``n``.
bgneal@65 33
bgneal@65 34 :param n: an integer between 0-5, inclusive. Key wheel 0 is the
bgneal@65 35 left-most wheel and wheel 5 is the right-most.
bgneal@65 36
bgneal@65 37 :param effective_pins: an iterable of letters whose pins are slid to
bgneal@65 38 the "effective" position (to the right). See :ref:`pin-settings`.
bgneal@65 39
bgneal@65 40 .. method:: set_all_pins(pin_list)
bgneal@65 41
bgneal@65 42 Sets all key wheel pins according to the supplied pin list.
bgneal@65 43
bgneal@65 44 :param pin_list: must either be ``None`` or a 6-element list of strings
bgneal@65 45 where each string element is as described in :ref:`pin-settings`.
bgneal@65 46 If ``None``, all pins in all key wheels are moved to the ineffective position.
bgneal@65 47
bgneal@65 48 .. method:: set_drum_lugs(lug_list)
bgneal@65 49
bgneal@65 50 Sets the drum lugs according to the given ``lug_list`` parameter.
bgneal@65 51
bgneal@65 52 If ``lug_list`` is ``None`` or empty, all lugs will be placed in neutral
bgneal@65 53 positions.
bgneal@65 54
bgneal@65 55 Otherwise, the ``lug_list`` can either be a list or a string.
bgneal@65 56
bgneal@65 57 If ``lug_list`` is passed a list, it must be a list of 1 or 2-tuple integers,
bgneal@65 58 where each integer is between 0-5, inclusive, and represents a 0-based
bgneal@65 59 key wheel position. The list can not be longer than 27 items. Only lug
bgneal@65 60 bars with lugs in non-neutral positions need be listed. Lug bars with one
bgneal@65 61 lug in a non-neutral position are represented by a 1-tuple. Bars with
bgneal@65 62 2 non-netural lugs are represented as a 2-tuple.
bgneal@65 63
bgneal@65 64 If ``lug_list`` is passed as a string, it is assumed to be in key list
bgneal@65 65 format as described in :ref:`lug-settings`.
bgneal@65 66
bgneal@65 67 Example::
bgneal@65 68
bgneal@65 69 m = M209()
bgneal@65 70 m.set_drum_lugs('1-0 2-0*2 0-3 0-5*3 0-6 2-4 3-6')
bgneal@65 71
bgneal@65 72 # or equivalently
bgneal@65 73 m.set_drum_lugs([(0, ), (1, ), (1, ), (2, ), (4, ), (4, ), (4, ), (5, ), (1, 3), (2, 5)])
bgneal@65 74
bgneal@65 75
bgneal@65 76 .. method:: set_key_wheel(n, c)
bgneal@65 77
bgneal@65 78 Set key wheel ``n`` to the letter ``c``.
bgneal@65 79
bgneal@65 80 :param n: an integer between 0-5 where key wheel 0 is the leftmost key wheel,
bgneal@65 81 and 5 is the rightmost
bgneal@65 82 :param c: a 1-letter string valid for key wheel ``n``
bgneal@65 83 :raises KeyWheelError: if ``c`` is not valid for wheel ``n``
bgneal@65 84
bgneal@65 85 .. method:: set_key_wheels(s)
bgneal@65 86
bgneal@65 87 Set the key wheels from left to right to the six letter string ``s``.
bgneal@65 88
bgneal@65 89 :raises KeyWheelError: if any letter in ``s`` is not valid for the corresponding key wheel
bgneal@65 90
bgneal@65 91 .. method:: set_random_key_wheels()
bgneal@65 92
bgneal@65 93 Sets the six key wheels to random letters.
bgneal@65 94
bgneal@65 95 :returns: a string of length six representing the new key wheel settings
bgneal@65 96
bgneal@65 97 .. method:: get_settings()
bgneal@65 98
bgneal@65 99 Returns the current key settings.
bgneal@65 100
bgneal@65 101 :returns: a named tuple of ``(lugs, pin_list)`` representing the current
bgneal@65 102 key settings. ``lugs`` will be in string format.
bgneal@65 103
bgneal@65 104 .. method:: encrypt(plaintext[, group=True[, spaces=True]])
bgneal@65 105
bgneal@65 106 Performs an encrypt operation on the given plaintext and returns the
bgneal@65 107 encrypted ciphertext as a string.
bgneal@65 108
bgneal@65 109 :param plaintext: the text string to encrypt
bgneal@65 110 :param group: if ``True``, the ciphertext string will be grouped into 5-letter
bgneal@65 111 groups, separated by spaces
bgneal@65 112 :param spaces: if ``True``, space characters in the input plaintext will
bgneal@65 113 automatically be treated as ``Z`` characters. Otherwise spaces in the
bgneal@65 114 plaintext will raise an ``M209Error``.
bgneal@65 115 :returns: the ciphertext as a string
bgneal@65 116
bgneal@65 117 .. method:: decrypt(ciphertext[, spaces=True[, z_sub=True]])
bgneal@65 118
bgneal@65 119 Performs a decrypt operation on the given ciphertext and returns the
bgneal@65 120 decrypted plaintext as a string.
bgneal@65 121
bgneal@65 122 :param ciphertext: the text string to decyrpt
bgneal@65 123 :param spaces: if ``True``, spaces will be allowed in the input ciphertext and
bgneal@65 124 ignored. Otherwise space characters will raise an ``M209Error``.
bgneal@65 125 This is useful if the input ciphertext is in 5-letter groups, separated
bgneal@65 126 by spaces.
bgneal@65 127 :param z_sub: if ``True``, ``Z`` characters in the output plaintext will be
bgneal@65 128 replaced by space characters, just like an actual M-209.
bgneal@65 129 :returns: the plaintext as a string
bgneal@65 130
bgneal@65 131 Example:
bgneal@65 132
bgneal@65 133 >>> from m209.converter import M209
bgneal@65 134 >>> m = M209()
bgneal@65 135 >>> m.set_drum_lugs('1-0 2-0*2 0-3 0-5*3 0-6 2-4 3-6')
bgneal@65 136 >>> pin_list = [
bgneal@65 137 ... 'FGIKOPRSUVWYZ',
bgneal@65 138 ... 'DFGKLMOTUY',
bgneal@65 139 ... 'ADEFGIORTUVX',
bgneal@65 140 ... 'ACFGHILMRSU',
bgneal@65 141 ... 'BCDEFJKLPS',
bgneal@65 142 ... 'EFGHIJLMNP'
bgneal@65 143 ... ]
bgneal@65 144 >>> m.set_all_pins(pin_list)
bgneal@65 145 >>> m.set_key_wheels('FFEGJP')
bgneal@65 146 >>> ct = m.encrypt('THE PIZZA HAS ARRIVED')
bgneal@65 147 >>> ct
bgneal@65 148 'QBCHU WCCDI YFNCH LOZJY G'
bgneal@65 149 >>> m.set_key_wheels('FFEGJP')
bgneal@65 150 >>> pt = m.decrypt(ct)
bgneal@65 151 >>> pt
bgneal@65 152 'THE PI A HAS ARRIVED'