rfc1982_serial_number/rfc1982_serial_number.py

#!/usr/bin/env python3

class Serial:

    _modulus = 2 ** 32
    _bitmask = _modulus - 1
    _signbit = _modulus >> 1

    def __init__(self, val):
        self._val = int(val) & self._bitmask

    def __add__(self, val):
        return self.__class__(self._val + int(val))

    def __le__(self, other):
        return (self._modulus - int(self) + int(other)) & self._signbit == 0

    def __ge__(self, other):
        return (self._modulus + int(self) - int(other)) & self._signbit == 0

    def __eq__(self, other):
        return int(self) == int(other)

    def __ne__(self, other):
        return int(self) != int(other)

    def __lt__(self, other):
        return self != other and self <= other

    def __gt__(self, other):
        return self != other and self >= other

    def __int__(self):
        return self._val

    def __str__(self):
        return str(int(self))

if __name__ == "__main__":
    from random import randint

    for test in range(100):
        i1 = Serial(randint(0, 2**32-1))
        i2 = Serial(randint(0, 2**32-1))

        assert i1 == i2 or \
            (i1 < i2 and not (i1 > i2)) or \
            (i1 > i2 and not (i1 < i2)) or \
            int(i1) & int(i2) == 0x80000000

        if i1 == i2:
            print(f"{int(i1):10d} == {int(i2):10d}, how did that happen?")
        elif i1 < i2:
            print(f"{int(i1):10d} => {int(i2):10d}, can do it in one jump")
        else:
            i3 = i1 + (2**31 - 2)
            print(f"{int(i1):10d} => {int(i2):10d}, need to wrap, i3 value {i3}")
            assert i1 < i3 and i3 < i2