much better input validation

calebTree · Aug 19, 2021 · f8704ad · f8704ad
1 parent 51bca63
commit f8704ad
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Showing 3 changed files with 39 additions and 34 deletions.
diff --git a/caesar-cipher.cpp b/caesar-cipher.cpp
@@ -1,27 +1,26 @@
 #include "caesar-cipher.h"
-#include <iostream>
 
 // https://www.tutorialspoint.com/cplusplus-program-to-implement-caesar-cypher
 // https://www.asciihex.com/
 
 using namespace std;
 
-void encryption(const string &plainAlpha, char &discard) {
+void encryption(const string &plainAlpha) {
     int key;
     string message, cipherAlphabet, cipherText;
 
     // input number of places to shift left
     cout << "Enter your chosen cipher key. (integer, 1-25): ";
     cin >> key;
     // input validation
-    if (key > 25 || key < 1) {
-        while (key > 25 || key < 1) {
-            cout << "Error! Enter an integer between 1 and 25: ";
-            cin >> key;
-        }
+    while (!cin || key > 25 || key < 1) {
+        cin.clear();
+        cin.ignore(numeric_limits<streamsize>::max(), '\n');
+        cout << "Error! Enter an integer between 1 and 25: ";
+        cin >> key;
     }
-    cin.get(discard);                                                   // discard \n
-    cout << "Enter the message to encrypt. (lowercase, roman alpha): ";     // input message to encrypt
+    cin.ignore(numeric_limits<streamsize>::max(), '\n');     // discard \n
+    cout << "Enter the message to encrypt: ";     // input message to encrypt
     getline(cin, message);
 
     // shift alphabet [key] letters to the left
@@ -35,21 +34,21 @@ void encryption(const string &plainAlpha, char &discard) {
     cout << "Ciphertext: " << cipherText << endl << endl;
 }
 
-void decryption(const string &plainAlpha, char &discard) {
+void decryption(const string &plainAlpha) {
     int key;
     string cipherText;
 
-    cout << "Enter the known cipher key. (integer, 1-25): ";
+    cout << "Enter your known cipher key. (integer, 1-25): ";
     cin >> key;
     // input validation
-    if (key > 25 || key < 1) {
-        while (key > 25 || key < 1) {
-            cout << "Error! Enter an integer between 1 and 25: ";
-            cin >> key;
-        }
+    while (!cin || key > 25 || key < 1) {
+        cin.clear();
+        cin.ignore(numeric_limits<streamsize>::max(), '\n');
+        cout << "Error! Enter an integer between 1 and 25: ";
+        cin >> key;
     }
-    cin.get(discard);                                                   // discard \n
-    cout << "Enter the message to decrypt. (lowercase, roman alpha): ";     // input message to decrypt
+    cin.ignore(numeric_limits<streamsize>::max(), '\n');                // discard \n
+    cout << "Enter the message to decrypt: ";     // input message to decrypt
     getline(cin, cipherText);
 
     cout << "\nCiphertext: " << cipherText << endl;

diff --git a/caesar-cipher.h b/caesar-cipher.h
@@ -4,21 +4,21 @@
 #endif //CAESAR_CIPHER_CAESAR_CIPHER_H
 
 #include <iostream>
+#include<limits>
+
 using namespace std;
 
-void encryption(const string&, char&);
+void encryption(const string&);
 // Function to display encrypt interface
-// Postcondition: string is the plain alphabet displayed and ciphered;
-//                char discards \n
+// Postcondition: const string is the alphabet displayed in plain then in ciphered
 
-void decryption(const string&, char&);
+void decryption(const string&);
 // Function to display decrypt interface
-// Postcondition: string is the plain alphabet displayed and ciphered;
-//                char discards \n
+// Postcondition: const string is the alphabet displayed in plain then in ciphered
 
 string cipherAlpha(int&, const string&);
 // Function to generate cipher alphabet.
-// Postcondition: const string shifted left by int positions
+// Postcondition: const string is shifted left by const int positions
 
 string cipherMessage(const string&, int&);
 // Function to encrypt the message

diff --git a/main.cpp b/main.cpp
@@ -6,28 +6,34 @@ using namespace std;
 int main() {
     cout << "\nWelcome to Julius Caesar's Shift Cipher!"
             "\nEnter an integer to shift the normal alphabet left by that number of positions." << endl;
-    cout << "Then, enter a message that will be encrypted using your cipher alphabet." << endl;
+    cout << "Then, enter a message that will be encrypted using the generated cipher alphabet." << endl;
     cout << "https://en.wikipedia.org/wiki/Caesar_cipher\n" << endl;
 
-    int option = -1;
+    int option;
     string plainAlpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
-    char discard;
 
-    while (option != 0) {
+    while (cin) {
         cout << "(1) Encrypt, (2) Decrypt, (0) Quit: ";
         cin >> option;
+        if (!cin) {
+            cin.clear();
+            cin.ignore(numeric_limits<streamsize>::max(), '\n');
+            cout << "Error! Invalid input." << endl;
+            continue;
+        }
         switch (option) {
             case 0:
-                break;
+                return 0;
             case 1:
-                encryption(plainAlpha, discard);
+                encryption(plainAlpha);
                 break;
             case 2:
-                decryption(plainAlpha, discard);
+                decryption(plainAlpha);
                 break;
             default:
-                cout << "Invalid choice." << endl;
+                cout << "Error! Invalid choice." << endl;
+                cin.clear();
+                cin.ignore(numeric_limits<streamsize>::max(), '\n');
         }
     }
-    return 0;
 }