Const correctness and const-ref in Crypto and elsewhere.

src/crypto/crypto.h

@@ -109,21 +109,21 @@ namespace Crypto {
 
   public:
     Nonce( uint64_t val );
-    Nonce( char *s_bytes, size_t len );
+    Nonce( const char *s_bytes, size_t len );
     
     string cc_str( void ) const { return string( bytes + 4, 8 ); }
     const char *data( void ) const { return bytes; }
-    uint64_t val( void );
+    uint64_t val( void ) const;
   };
   
   class Message {
   public:
-    Nonce nonce;
-    string text;
+    const Nonce nonce;
+    const string text;
     
-    Message( char *nonce_bytes, size_t nonce_len,
-	     char *text_bytes, size_t text_len );
-    Message( Nonce s_nonce, string s_text );
+    Message( const char *nonce_bytes, size_t nonce_len,
+	     const char *text_bytes, size_t text_len );
+    Message( const Nonce & s_nonce, const string & s_text );
   };
   
   class Session {
@@ -145,8 +145,8 @@ namespace Crypto {
     Session( Base64Key s_key );
     ~Session();
     
-    string encrypt( Message plaintext );
-    Message decrypt( string ciphertext );
+    const string encrypt( const Message & plaintext );
+    const Message decrypt( const string & ciphertext );
     
     Session( const Session & );
     Session & operator=( const Session & );