crc.py

def crc_check(data,div):
    l=len(div)
    ct=0
    data=[int(i) for i in data]
    div=[int(i) for i in div]
    zero=[0 for i in range(l)]
    temp_data=[data[i] for i in range(l)]
    result=[]
    for j in range(len(data)-len(div)+1):
        print("Temp_dividend",temp_data)  
        msb=temp_data[0]
        if msb==0:
            result.append(0)
            for i in range(l-1,-1,-1):
                temp_data[i]=temp_data[i] ^ zero[i]
        else:
            result.append(1)
            for i in range(l-1,-1,-1):
                temp_data[i]=temp_data[i] ^ div[i]
        temp_data.pop(0)
        if (l+j<len(data)):
            temp_data.append(data[l+j])
    crc=temp_data
    print("Quotient: ",result,"remainder",crc)
    return crc

while 1>0:
    print("Enter data: ")
    data=input()
    print("Enter divisor")
    div=input()
    original_data=data
    data=data+("0"*(len(div)-1))
    crc=crc_check(data,div)
    crc_str=""
    for i in range(len(crc)):
        crc_str+=str(crc[i])
    print("Sent data: ",original_data+crc_str)
    sent_data=original_data+crc_str
    print("If again applying CRC algorithm, the remainder/CRC must be zero if errorless.")
    crc=crc_check(sent_data,div)
    remainder=crc
    print("Receiver side remainder: ",remainder)
    print("Continue [Y/N]:")
    ch=input()
    if ch=='N' or ch=='n':
        break
    else:
        continue