crc.cpp

crc.cpp

#include <iostream>
#include <bitset>
using namespace std;

string POLYNOMIAL = "10001000000100001";


string TextToBinaryString(string words) {
    string binaryString = "";
    for (char& _char : words) {
        binaryString +=bitset<8>(_char).to_string();
    }
    return binaryString;
}

string ComputeCRC(string bin_msg){
    
    string encoded = "";
    int msg_len = bin_msg.length(), poly_len = POLYNOMIAL.length();
    encoded += bin_msg;

    for(int i=1; i <= poly_len - 1; i++){
        encoded += '0';  
    }

    for(int i = 0; i <= encoded.length() - poly_len;){
        for(int j = 0; j < poly_len; j++){
            encoded[i+j] = encoded[i+j] == POLYNOMIAL[j] ? '0' : '1';
        }
        for(; i < encoded.length() && encoded[i] != '1'; i++);
    }

    return encoded.substr(encoded.length() - poly_len + 1);
}
void receiver() {
    string msg, crc;
    cout << "Enter message : ";
    getline(cin, msg);
    cout << "Enter crc : ";
    getline(cin, crc);

    string bin_msg = TextToBinaryString(msg);
    string computed_crc = ComputeCRC(bin_msg + crc);

    cout << "Computed CRC: " << computed_crc << endl;

    if(computed_crc.find('1') != std::string::npos){
        cout << "Error Detected. (Msg Rejected)" << endl;
    }else{
        cout << "No Error Detected. (Msg Accepted)" << endl;
    }


}
void sender(){
    string msg;
    cout << "Enter the message : "; 
    getline(cin, msg);

    string bin_msg = TextToBinaryString(msg);
    
    string sender_crc = ComputeCRC(bin_msg);

    cout << sender_crc << endl;
}



int main(int argc, char const *argv[])
{
    /* code */
    cout << "Sender" << endl;
    sender();
    cout << "Receiver" << endl;
    receiver();
    return 0;
}