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104 lines
3.6 KiB
Python
104 lines
3.6 KiB
Python
# ===================================================================
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#
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# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in
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# the documentation and/or other materials provided with the
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# distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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# ===================================================================
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from Crypto.Util.number import long_to_bytes, bytes_to_long
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class Natural(object):
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"""A class to model a natural integer (including zero)"""
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def __init__(self, value):
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if isinstance(value, float):
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raise ValueError("A floating point type is not a natural number")
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if value < 0:
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raise ValueError("A natural number is not negative")
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self._value = value
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def to_bytes(self, block_size=0):
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return long_to_bytes(self._value, block_size)
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def __int__(self):
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return self._value
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@staticmethod
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def from_bytes(byte_string):
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return Natural(bytes_to_long(byte_string))
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# Arithmetic operations
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def __add__(self, term):
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try:
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return Natural(self._value + term._value)
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except AttributeError:
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return Natural(self._value + term)
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def __sub__(self, term):
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try:
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diff = self._value - term._value
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except AttributeError:
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diff = self._value - term
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if diff < 0:
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raise ValueError("Result of subtraction is not a natural value")
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return Natural(diff)
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def __mod__(self, divisor):
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try:
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return Natural(self._value % divisor._value)
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except AttributeError:
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return Natural(self._value % divisor)
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def __pow__(self, exponent):
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try:
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return Natural(self._value ** exponent._value)
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except AttributeError:
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return Natural(self._value ** exponent)
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def __rpow__(self, base):
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try:
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return Natural(base._value ** self._value)
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except AttributeError:
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return Natural(base ** self._value)
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# Relations
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def __eq__(self, term):
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try:
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result = self._value == term._value
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except AttributeError:
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result = self._value == term
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return result
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def __ne__(self, term):
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return not self.__eq__(term)
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def __lt__(self, term):
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try:
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result = self._value < term._value
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except AttributeError:
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result = self._value < term
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return result
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