Calculate Header TAGS

mktag.py

#!/usr/bin/env python3

import argparse
import operator

from functools import reduce

def mktag(tag: str) -> int:
    letters = [i for i in tag]
    letters.reverse()
    ords = [ord(i) for i in letters]
    shifted = [operator.lshift(i, counter*8) for counter, i in enumerate(ords)]
    return reduce(operator.or_, shifted)

def test() -> None:
    assert mktag("CASt") == 1128354676

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description='Calculate TAG.')
    parser.add_argument('tag', type=str, help='Tag to be calculated')
    parser.add_argument('--test', help="run the test suite.",
            action="store_true")
    args = parser.parse_args()
    if args.test:
        test()
    else:
        print(mktag(args.tag))