CRC calculator using the XModem algorithm.

XModemCrcCalculator.py

#!/usr/bin/python
"""
Given a file containing hexadecimal numbers (one number per line), 
returns the XModem CRC of these numbers.

Note: This scrip uses the thist party library `crcmod`. 
      you may isntall it using `pip install crcmod`
      More info available here: 
          https://pypi.python.org/pypi/crcmod
"""

import binascii
import crcmod
import argparse


def main():
    args = parse_input_arguments()
    crc = calculate_crc(open(args.input_filename, 'r'))
    print('The calculated CRC is: ' + crc)


def parse_input_arguments():
    """
    Parse the input arguments.

    @return args: Arguments provided by the user.
    """
    parser = argparse.ArgumentParser()
    parser.add_argument("-i", "--input",
                        dest="input_filename",
                        help="Input file",
                        metavar="FILE")

    args  = parser.parse_args()
    return args


def calculate_crc(data_stream):
    """
    Given a file containing hexadecimal numbers, returns the XModem CRC of these
    numbers.

    @param data_stream: iterable object containing hex data (str format).
    @return CRC (XModem algorithm): Hex string containing the calculated CRC.
    """

    xmodem_crc = crcmod.Crc(0x11021, initCrc=0, rev=False, xorOut=0x0000)

    for dataword in data_stream:
        xmodem_crc.update(binascii.a2b_hex(dataword.strip()))

    return xmodem_crc.hexdigest()


if __name__ == "__main__":
    main()