DALGLI0/crc16.py

from poly import Polynomial
import sys
import ast

Polynomial.n = 2

def normalize_byte(data):
    while len(data) != 8:
        if len(data) < 8:
            data = str(0) + data
        else:
            data = data[1:]
    return data


def encode(in_data):
    data = in_data
    data = list(data)
    data_binary = [bin(ord(char)).replace('b', '') for char in data]
    data_binary = [normalize_byte(byte) for byte in data_binary]
    data_binary = [int(bit) for bit in list(''.join(data_binary))]
    data_binary.reverse()

    M = [0] * 16 + data_binary
    L = [0] * (len(data_binary)) + [1] * 16
    G = [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1]
    result_poly = Polynomial.divide(Polynomial.add(Polynomial(M), Polynomial(L)), Polynomial(G))
    result = result_poly.coefficients + [0] * (16 - len(result_poly.coefficients))

    result.reverse()
    data_binary.reverse()
    data_binary = data_binary + result
    data_binary = [data_binary[i:i+8] for i in range(0, len(data_binary), 8)]
    data_binary = [int(''.join(map(str, byte)), 2) for byte in data_binary]

    fcs = [hex(byte) for byte in data_binary]
    fcs = fcs[-2:]

    data = [chr(byte) for byte in data_binary]
    data = ''.join(data[0:-2])

    return data, fcs


def check_fcs(in_data, fcs):
    data = in_data
    data = list(data)
    data_binary = [bin(ord(char)).replace('b', '') for char in data]
    data_binary = [normalize_byte(byte) for byte in data_binary]
    data_binary = [int(bit) for bit in list(''.join(data_binary))]
    fcs_binary = [bin(int(in_hex, 16)).replace('b', '') for in_hex in fcs]
    fcs_binary = [normalize_byte(byte) for byte in fcs_binary]
    fcs_binary = [int(bit) for bit in list(''.join(fcs_binary))]
    data_binary += fcs_binary
    data_binary.reverse()

    C = [0] * 16 + data_binary
    L = [0] * len(data_binary) + [1] * 16
    G = [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1]
    S = Polynomial.divide(Polynomial.add(Polynomial(C), Polynomial(L)), Polynomial(G))

    if S.coefficients == []:
        return True

    return False


def main():
    try:
        if sys.argv[1] == '-e' or sys.argv[1] == '-encode':
            arg, fcs = encode(sys.argv[2])
            print(arg, fcs)
            print(check_fcs(arg, fcs)) # powinno zawsze zwracać true
        elif sys.argv[1] == '-c' or sys.argv[1] == '-check':
            arg = sys.argv[2]
            fcs = ast.literal_eval(sys.argv[3])
            print(check_fcs(arg, fcs))
        else:
            raise IndexError
    except IndexError:
        print("To encode: python3 CRC16.py -e [argument]\nTo check result: python3 CRC16.py -c [argument] [fcs]")


if __name__ == "__main__":
    main()