Python: unsigned 32 bit bitwise arithmetic

Trying to answer to another post whose solution deals with IP addresses and netmasks, I got stuck with plain bitwise arithmetic.

Is there a standard way, in Python, to carry on bitwise AND, OR, XOR, NOT operations assuming that the inputs are "32 bit" (maybe negative) integers or longs, and that the result must be a long in the range [0, 2**32]?

In other words, I need a working Python counterpart to the C bitwise operations between unsigned longs.

EDIT: the specific issue is this:

>>> m = 0xFFFFFF00   # netmask 255.255.255.0
>>> ~m
-4294967041L         # wtf?! I want 255


Asked by: Hailey772 | Posted: 05-10-2021






Answer 1

You can use ctypes and its c_uint32:

>>> import ctypes
>>> m = 0xFFFFFF00
>>> ctypes.c_uint32(~m).value
255L

So what I did here was casting ~m to a C 32-bit unsigned integer and retrieving its value back in Python format.

Answered by: Andrew157 | Posted: 06-11-2021



Answer 2

You can mask everything by 0xFFFFFFFF:

>>> m = 0xFFFFFF00
>>> allf = 0xFFFFFFFF
>>> ~m & allf
255L

Answered by: Melissa285 | Posted: 06-11-2021



Answer 3

from numpy import uint32

Answered by: Eric935 | Posted: 06-11-2021



Answer 4

You could also xor with 0xFFFFFFFF, which is equivalent to the "unsigned complement".

>>> 0xFFFFFF00 ^ 0xFFFFFFFF
255

Answered by: Caroline565 | Posted: 06-11-2021



Answer 5

This is a module that I created a long time ago, and it might be of help to you:

IPv4Utils

It provides at least a CIDR class with subnet arithmetic. Check the test cases at the end of the module for examples.

Answered by: Ned292 | Posted: 06-11-2021



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