Added encoder function

Fixed XOR operator
TODO - Add boilerplate from syllabus file, then merge with main branch

Codes/CRC.cpp

@@ -2,25 +2,47 @@
 #include <cstring>
 using namespace std;
 
-
 string XOR(string data, string key) {
     // Dividend is data
     // Divisor is the primary key, i.e. the key
     string result = "";
-    int len = data.length();
+    int dataLen = data.length();
+    int keyLen = key.length();
 
-    // Performing XOR operation
+    // Perform XOR operation
-    for (int i=0; i<len; i++) {
+    for (int i=0; i<keyLen; i++) {
+        if (i < dataLen) {
+            // Only perform XOR if within the length of data
             if (data[i] == key[i]) {
-            result = result + "0";
+                result += '0';
             }
             else {
-            result = result + "1";
+                result += '1';
+            }
+        } else {
+            // If data length exceeded, append the key
+            result += key[i];
         }
     }
     return result;
 }
 
+string encoder(string data, string key) {
+    int keyLen = key.length();
+
+    // Append n-1 zeroes to the data
+    string dataWithZeroes = data + string(keyLen-1, '0');
+
+    // Perform XOR operation with the key
+    string remainder = XOR(dataWithZeroes, key);
+
+    // Get the remainder (last n-1 bits)
+    string crc = remainder.substr(remainder.length() - (keyLen-1));
+
+    // Append the CRC to the original data
+    return data + crc;
+}
+
 int main() {
     string data, key;
 
@@ -29,8 +51,13 @@ int main() {
     cout << "Enter primary key:\t";
     getline(cin, key);
 
-	cout<<XOR(data, key);
+    string messageToSend = encoder(data, key);
+    cout<<endl<<"--------------------"<<endl;
+    cout<<"Message to be sent:\t"<<messageToSend;
+    cout<<endl<<"--------------------"<<endl;
 
     return 0;
-
 }
+
+// TODO:
+// - Check if input data is actually binary