diff options
| -rw-r--r-- | rfc1982_serial_number.py | 47 |
1 files changed, 27 insertions, 20 deletions
diff --git a/rfc1982_serial_number.py b/rfc1982_serial_number.py index a8c29d7..5344b91 100644 --- a/rfc1982_serial_number.py +++ b/rfc1982_serial_number.py @@ -2,21 +2,27 @@ class Serial: - _modulus = 2 ** 32 - _bitmask = _modulus - 1 - _signbit = _modulus >> 1 + modulus = 2 ** 32 + + @property + def bitmask(self): + return self.modulus - 1 + + @property + def signbit(self): + return self.modulus >> 1 def __init__(self, val): - self._val = int(val) & self._bitmask + self._val = int(val) & self.bitmask def __add__(self, val): - return self.__class__(self._val + int(val)) + return type(self)(self._val + int(val)) def __le__(self, other): - return (self._modulus - int(self) + int(other)) & self._signbit == 0 + return (self.modulus - int(self) + int(other)) & self.signbit == 0 def __ge__(self, other): - return (self._modulus + int(self) - int(other)) & self._signbit == 0 + return (self.modulus + int(self) - int(other)) & self.signbit == 0 def __eq__(self, other): return int(self) == int(other) @@ -34,25 +40,26 @@ class Serial: return self._val def __str__(self): - return str(int(self)) + return f"{int(self):{len(str(self.modulus))}d}" + +def step(start, finish): + if start < finish: + return start, finish + else: + midpoint = start + ((Serial.modulus >> 1) - 2) + assert start < midpoint and midpoint < finish + return start, midpoint, finish 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)) + i1 = Serial(randint(0, Serial.modulus - 1)) + i2 = Serial(randint(0, Serial.modulus - 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 + int(i1) & int(i2) == Serial.modulus >> 1 + + print(f"{i1} => {i2}: {', '.join(str(s) for s in step(i1, i2))}") |