From b94dba6141c2cf7d801655443f7b481fa8f55456 Mon Sep 17 00:00:00 2001
From: Kshitij <kshitijk@tuta.io>
Date: Mon, 29 Jul 2024 19:57:00 +0530
Subject: [PATCH] Added encoder function Fixed XOR operator TODO - Add
 boilerplate from syllabus file, then merge with main branch

---
 Codes/CRC.cpp | 61 +++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 44 insertions(+), 17 deletions(-)

diff --git a/Codes/CRC.cpp b/Codes/CRC.cpp
index 5d61e8c..2e1a9d7 100644
--- a/Codes/CRC.cpp
+++ b/Codes/CRC.cpp
@@ -2,35 +2,62 @@
 #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
-    for (int i=0; i<len; i++) {
-        if (data[i] == key[i]) {
-            result = result + "0";
-        }
-        else {
-            result = result + "1";
+    // Perform XOR operation
+    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 += '0';
+            }
+            else {
+                result += '1';
+            }
+        } else {
+            // If data length exceeded, append the key
+            result += key[i];
         }
     }
     return result;
 }
 
-int main() {
-	string data, key;
+string encoder(string data, string key) {
+    int keyLen = key.length();
 
-	cout<<endl<<"Enter data:\t";
-	getline(cin, data);
-	cout<<"Enter primary key:\t";
-	getline(cin, key);
+    // Append n-1 zeroes to the data
+    string dataWithZeroes = data + string(keyLen-1, '0');
 
-	cout<<XOR(data, key);
+    // Perform XOR operation with the key
+    string remainder = XOR(dataWithZeroes, key);
 
-	return 0;
+    // 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;
+
+    cout << endl << "Enter data:\t";
+    getline(cin, data);
+    cout << "Enter primary key:\t";
+    getline(cin, 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