ad atbash encryption

include/Crypt.h

@@ -7,13 +7,15 @@ class Crypt {
  public :
   Crypt();
 
-  static std::string cesar( std::string sentance, int key );
-  static std::string vigenere( std::string sentance, std::string key );
+  static std::string cesar( std::string sentance, int key, char start = 'a', char end = 'z' );
+  static std::string vigenere( std::string sentance, std::string key, char start = 'a', char end = 'z' );
+  static std::string atbash( std::string sentane, char start = 'a', char end = 'z' );
 
-  static char replaceChar( char character, int key);
+  static char replaceChar( char character, int key, char start = 'a', char end = 'z' );
   static char loopInString( std::string str, int key );
-  static int alphabetIndex( char ch );
-
+  static int alphabetIndex( char ch, char start = 'a', char end = 'z' );
+  static bool isLetter( char ch, char start = 'a', char end = 'z' );
+  
  private :
   
 };

main.cpp

@@ -1,6 +1,9 @@
 #include <iostream>
 #include "include/Crypt.h"
 
+const char START = 'a';
+const char END = 'z';
+
 /**
  @brief Take a string on command line argument to encrypt it. For vigenere encnyption, the text is encrypted with itself as a key
  **/
@@ -10,6 +13,7 @@ int main( int argc, char* argv[]  )
   std::cout << "to encrypt :" << txt << std::endl;
   std::cout << "code cesar :" <<  Crypt::cesar(txt, 3 ) << std::endl ;
   std::cout << "code vigenere :" << Crypt::vigenere(txt, txt ) << std::endl ;
-
+  std::cout << "code atbash :" << Crypt::atbash( txt ) << std::endl ;
+  
   return 0;
 }

src/Crypt.cpp

@@ -11,11 +11,13 @@ Crypt::Crypt(){
  @parameter key, the distance to shift
  @return string, the encrypted sentance
  **/
-std::string Crypt::cesar( std::string sentances, int key ){
+std::string Crypt::cesar( std::string sentances, int key, char start, char end ){
   std::string result = "";
 
   for( char character : sentances ){
-    result += Crypt::replaceChar( character, key ) ;
+    result += Crypt::isLetter( character, start, end )?
+      Crypt::replaceChar( character, key, start, end ) :
+	character;
   }
   
   return result;
@@ -28,14 +30,31 @@ std::string Crypt::cesar( std::string sentances, int key ){
  @see alphabet
  @return string, the vigenere encrypted sentance
  **/
-std::string Crypt::vigenere( std::string sentance, std::string key ){
+std::string Crypt::vigenere( std::string sentance, std::string key, char start, char end ){
   std::string result = "";
   int k = 0;
   int count = 1;
 
   for( char character : sentance ){
-    k = alphabetIndex( loopInString( key, count++ ));
-    result += Crypt::replaceChar( character, k ) ;
+    k = alphabetIndex( loopInString( key, count++ ), start, end);
+    result += Crypt::replaceChar( character, k, start, end ) ;
+  }
+  
+  return result;
+}
+
+std::string Crypt::atbash( std::string sentance, char start, char end ){
+  std::string result = "";
+  int k = 0;
+  int max = (int)end ;
+
+  for( char character : sentance ){
+    if( Crypt::isLetter( character, start, end ) ){
+      k = Crypt::alphabetIndex( character, start, end ) ;
+      result += (char)( max - k + 1) ;
+    }else{
+      result += character;
+    }
   }
   
   return result;
@@ -47,20 +66,17 @@ std::string Crypt::vigenere( std::string sentance, std::string key ){
  @parameter int key, the distance to look at
  @return string, the replacement character
  **/
-char Crypt::replaceChar( char ch, int key ){
+char Crypt::replaceChar( char ch, int key, char start, char end ){
   ch = (char)std::tolower( ch );
-  char a = 'a';
-  char z = 'z';
-  int max = (int)z;
-  int min = (int)a;
+  int max = (int)end;
 
-  if(( (int)ch < min ) || ( ch > max )){
+  if( !Crypt::isLetter( ch, start, end ) ){
     return ch;
   }
   
   if( (ch + key) > max ){
     key -= (max - (int)ch);
-    ch = 'a';
+    ch = start;
   }
 
   return (char)((int)ch + key);
@@ -81,17 +97,25 @@ char Crypt::loopInString( std::string str, int key ){
  @paramater char ch, the character to look at
  @return int, ordered index in the alphabet
  **/
-int Crypt::alphabetIndex( char ch ){
+int Crypt::alphabetIndex( char ch, char start, char end ){
   ch = (char)std::tolower( ch );
+  int min = (int)start;
 
-  char a = 'a';
-  char z = 'z';
-  int max = (int)z;
-  int min = (int)a;
-
-  if(( (int)ch < min ) || ( (int)ch > max )){
-    return ch;
+  if( Crypt::isLetter( ch, start, end ) ){
+    return int(ch) - min + 1;
   }
   
-  return int(ch) - min + 1;
+  return ch;
+}
+
+/** isLetter
+ @brief Return true is the character is a letter, which is the range between start and end
+ **/
+bool Crypt::isLetter( char ch, char start, char end ){
+  ch = (char)std::tolower( ch );
+
+  if(( (int)ch < (int)start ) || ( (int)ch > (int)end )){
+    return false;
+  }
+  return true;
 }