rom_filter: copy input node content to output node

Add suppport for copying the content of an 'input' node to the 'output'
node.

Issue #2558.

repos/os/src/server/rom_filter/README

@@ -30,6 +30,10 @@ The '<output>' node can contain the following sub nodes:
   sub node is evaluated. Each of those sub nodes can contain the same
   nodes as the '<output>' node.
 
+:'<input>':
+  Copies all sub nodes named by the 'sub_node' attribute of the input ROM
+  specified by the 'name' attribute to the output node.
+
 
 Conditions
 ----------

repos/os/src/server/rom_filter/input_rom_registry.h

@@ -54,6 +54,7 @@ class Rom_filter::Input_rom_registry
 		 * Exception type
 		 */
 		class Nonexistent_input_value { };
+		class Nonexistent_input_node  { };
 
 	private:
 
@@ -191,6 +192,15 @@ class Rom_filter::Input_rom_registry
 
 					throw Nonexistent_input_value();
 				}
+
+				Xml_node node() const
+				{
+					try {
+						return Xml_node(_top_level);
+					} catch (...) { }
+
+					throw Nonexistent_input_node();
+				}
 		};
 
 		Genode::Allocator &_alloc;
@@ -372,6 +382,21 @@ class Rom_filter::Input_rom_registry
 
 			return input_value;
 		}
+
+		/**
+		 * Lookup content of input with specified name
+		 *
+		 * \throw Nonexistent_input_value
+		 */
+		Xml_node xml(Input_name const &input_name) const
+		{
+			Entry const *e = _lookup_entry_by_name(input_name);
+
+			if (!e)
+				throw Nonexistent_input_node();
+
+			return e->node();
+		}
 };
 
 #endif /* _INPUT_ROM_REGISTRY_H_ */

repos/os/src/server/rom_filter/main.cc

@@ -310,6 +310,26 @@ void Rom_filter::Main::_evaluate_node(Xml_node node, Xml_generator &xml)
 			for (; src_len > 0 && Genode::is_whitespace(src[src_len - 1]); src_len--);
 
 			xml.append(src, src_len);
+		} else
+
+		if (node.has_type("input")) {
+			typedef Genode::String<128> String;
+
+			Input_name const input_name =
+				node.attribute_value("name", Input_name());
+
+			String const sub_node =
+				node.attribute_value("sub_node", String());
+
+			if (!sub_node.valid())
+				return;
+
+			try {
+				Xml_node input_node = _input_rom_registry.xml(input_name);
+
+				input_node.for_each_sub_node(sub_node.string(),
+				[&] (Xml_node node) { xml.append(node.addr(), node.size()); });
+			} catch (...) { }
 		}
 	};