From e0081cfc29b33acad307edad64768e3a58dfb572 Mon Sep 17 00:00:00 2001
From: Martin Stein <martin.stein@genode-labs.com>
Date: Tue, 13 Mar 2018 18:00:53 +0100
Subject: [PATCH] nic_router: safe pointer class for const objects

Const_pointer class that enables the use of the pointer wrapper for
const ojects.

Ref #2670
---
 repos/os/src/server/nic_router/pointer.h | 39 +++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/repos/os/src/server/nic_router/pointer.h b/repos/os/src/server/nic_router/pointer.h
index 90e95308f8..cf74d2dbaf 100644
--- a/repos/os/src/server/nic_router/pointer.h
+++ b/repos/os/src/server/nic_router/pointer.h
@@ -17,7 +17,11 @@
 /* Genode includes */
 #include <base/exception.h>
 
-namespace Net { template <typename> class Pointer; }
+namespace Net {
+
+	template <typename> class Pointer;
+	template <typename> class Const_pointer;
+}
 
 template <typename T>
 class Net::Pointer
@@ -54,4 +58,37 @@ class Net::Pointer
 		void unset() { _ptr = nullptr; }
 };
 
+template <typename T>
+class Net::Const_pointer
+{
+	private:
+
+		T const *_ptr;
+		bool     _valid;
+
+	public:
+
+		struct Valid   : Genode::Exception { };
+		struct Invalid : Genode::Exception { };
+
+		Const_pointer() : _ptr(nullptr), _valid(false) { }
+
+		Const_pointer(T const &ref) : _ptr(&ref), _valid(true) { }
+
+		T const &deref() const
+		{
+			if (!_valid) { throw Invalid(); }
+			return *_ptr;
+		}
+
+		void set(T const &ptr)
+		{
+			if (_valid) { throw Valid(); }
+			_ptr = &ptr;
+			_valid = true;
+		}
+
+		void unset() { _valid = false; }
+};
+
 #endif /* _POINTER_H_ */