Added tins_cast as a replacement for dynamic_cast when using it on PDU classes.

include/crypto.h

@@ -49,7 +49,7 @@ namespace Crypto {
     /**
      * \cond
      */
-    class RC4Key;
+    struct RC4Key;
     #ifdef HAVE_WPA2_DECRYPTION
     namespace WPA2 {
         class invalid_handshake : public std::exception {

include/exceptions.h

@@ -145,6 +145,16 @@ public:
         return "Malformed option";
     }
 };
+
+/**
+ * \brief Exception thrown when a call to tins_cast fails.
+ */
+class bad_tins_cast : public std::exception {
+public:
+    const char *what() const throw() {
+        return "Bad Tins cast";
+    }
+};
 }
 
 #endif // TINS_EXCEPTIONS_H

include/pdu.h

@@ -456,6 +456,34 @@ namespace Tins {
         *lop /= rop;
         return lop;
     }
+
+    namespace Internals {
+        template<typename T>
+        struct remove_pointer {
+            typedef T type;
+        };
+
+        template<typename T>
+        struct remove_pointer<T*> {
+            typedef T type;
+        };
+    }
+
+    template<typename T, typename U>
+    T tins_cast(U *pdu) {
+        typedef typename Internals::remove_pointer<T>::type TrueT;
+        return pdu && (TrueT::pdu_flag == pdu->pdu_type()) ?
+            static_cast<T>(pdu) :
+            0;
+    }
+
+    template<typename T, typename U>
+    T &tins_cast(U &pdu) {
+        T *ptr = tins_cast<T*>(&pdu);
+        if(!ptr)
+            throw bad_tins_cast();
+        return *ptr;
+    }
 }
 
 #endif // TINS_PDU_H