Convenience helper for attached ROM dataspaces

In the line of the 'Attached_ram_dataspace' and
'Attached_io_mem_dataspace' classes, this new helper simplifies the
access to ROM dataspaces.

os/include/os/attached_rom_dataspace.h

@@ -0,0 +1,78 @@
+/*
+ * \brief  ROM dataspace utility
+ * \author Norman Feske
+ * \date   2012-01-09
+ */
+
+/*
+ * Copyright (C) 2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__OS__ATTACHED_ROM_DATASPACE_H_
+#define _INCLUDE__OS__ATTACHED_ROM_DATASPACE_H_
+
+#include <rom_session/connection.h>
+#include <dataspace/client.h>
+#include <base/env.h>
+
+namespace Genode {
+
+	class Attached_rom_dataspace
+	{
+		private:
+
+			Rom_connection            _rom;
+			Rom_dataspace_capability  _ds;
+			size_t                    _size;
+			void                     *_local_addr;
+
+		public:
+
+			/**
+			 * Constructor
+			 *
+			 * \throw Rom_connection::Rom_session_failed
+			 * \throw Rm_session::Attach_failed
+			 */
+			Attached_rom_dataspace(char const *name)
+			:
+				_rom(name),
+				_ds(_rom.dataspace()),
+				_size(Dataspace_client(_ds).size()),
+				_local_addr(env()->rm_session()->attach(_ds))
+			{ }
+
+			/**
+			 * Destructor
+			 */
+			~Attached_rom_dataspace()
+			{
+				env()->rm_session()->detach(_local_addr);
+			}
+
+			/**
+			 * Return capability of the used ROM dataspace
+			 */
+			Rom_dataspace_capability cap() const { return _ds; }
+
+			/**
+			 * Request local address
+			 *
+			 * This is a template to avoid inconvenient casts at
+			 * the caller. A newly allocated ROM dataspace is
+			 * untyped memory anyway.
+			 */
+			template <typename T>
+			T *local_addr() { return static_cast<T *>(_local_addr); }
+
+			/**
+			 * Return size
+			 */
+			size_t size() const { return _size; }
+	};
+}
+
+#endif /* _INCLUDE__OS__ATTACHED_ROM_DATASPACE_H_ */