Esempio n. 1
0
def _block_to_indices(block):
    if len(block) > 4:
        raise ValueError("block too big")

    # `menmonicode` uses little-endian numbers.
    num = from_base(256, reversed(block))

    indices = list(reversed(to_base(1626, num)))

    # Pad the list of indices to the correct size.
    length = {
        1: 1,
        2: 2,
        3: 3,
        4: 3,
    }[len(block)]
    indices += [0] * (length - len(indices))

    # The third byte in a block slightly leaks into the third word.  A
    # different set of words is used for this case to distinguish it from the
    # four byte case.
    if len(block) == 3:
        indices[-1] += 1626

    return indices
Esempio n. 2
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def _block_to_indices(block):
    if len(block) > 4:
        raise ValueError("block too big")

    # menmonicode uses little-endian numbers
    num = from_base(256, reversed(block))

    indices = list(reversed(to_base(1626, num)))

    # pad the list of indices to the correct size
    length = {
        1: 1,
        2: 2,
        3: 3,
        4: 3,
    }[len(block)]
    indices += [0] * (length - len(indices))

    # The third byte in a block slightly leaks into the third word.  A
    # different set of words is used for this case to distinguish it from the
    # four byte case
    if len(block) == 3:
        indices[-1] += 1626

    return indices
Esempio n. 3
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def _words_to_block(words):
    if not isinstance(words, tuple):
        raise TypeError("expected tuple of words")

    if len(words) == 0:
        raise ValueError("no words in block")

    if len(words) > 3:
        raise ValueError("too many words in block")

    try:
        indices = list(word_to_index(word) for word in words)
    except KeyError as e:
        raise ValueError("word not recognized") from e

    # calculate length of block.
    # both three byte and four byte blocks map to three words but can be
    # distinguished as a different word list is used to encode the last word
    # in the three byte case
    length = {
        1: 1,
        2: 2,
        3: 3 if indices[-1] >= 1626 else 4,
    }[len(words)]

    if length == 3:
        indices[2] -= 1626

    # check that words in the second word list don't appear anywhere else in
    # the block
    for index in indices:
        if index > 1626:
            raise ValueError(
                "unexpected three byte word: %s" % index_to_word(index)
            )

    num = from_base(1626, reversed(indices))

    block = bytes(reversed(to_base(256, num)))

    # pad to correct length
    return block.ljust(length, b'\x00')
Esempio n. 4
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def _words_to_block(words):
    if not isinstance(words, tuple):
        raise TypeError("expected tuple of words")

    if len(words) == 0:
        raise ValueError("no words in block")

    if len(words) > 3:
        raise ValueError("too many words in block")

    try:
        indices = list(word_to_index(word) for word in words)
    except KeyError as e:
        raise ValueError("word not recognized") from e

    # Calculate length of block.
    # Both three byte and four byte blocks map to three words but can be
    # distinguished as a different word list is used to encode the last word
    # in the three byte case.
    length = {
        1: 1,
        2: 2,
        3: 3 if indices[-1] >= 1626 else 4,
    }[len(words)]

    if length == 3:
        indices[2] -= 1626

    # Check that words in the second word list don't appear anywhere else in
    # the block.
    for index in indices:
        if index > 1626:
            raise ValueError((
                "unexpected three byte word: {word!r}"
            ).format(word=index_to_word(index)))

    num = from_base(1626, reversed(indices))

    block = bytes(reversed(to_base(256, num)))

    # Pad to correct length.
    return block.ljust(length, b'\x00')
Esempio n. 5
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 def test_encode_base_ten(self):
     self.assertEqual([1, 2, 3, 4, 5, 6], to_base(10, 123456))
Esempio n. 6
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 def test_encode_zero(self):
     self.assertEqual([], to_base(12, 0))
Esempio n. 7
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 def test_encode_base_ten(self):
     self.assertEqual([1, 2, 3, 4, 5, 6], to_base(10, 123456))
Esempio n. 8
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 def test_encode_zero(self):
     self.assertEqual([], to_base(12, 0))