noux: Decouple Dir_file_system from file systems

By introducing the new 'File_system_registry', we can remove the
knowledge about the actual file-system implementations from the
'Dir_file_system'. Thereby the code becomes more generic, which is
a precondition for using it as the basis for Genode's VFS library.

Issue #999

ports/src/noux/block_file_system.h

@@ -271,7 +271,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "block"; }
+			static char const *name() { return "block"; }
 
 
 			/********************************

ports/src/noux/dataspace_registry.h

@@ -16,6 +16,7 @@
 
 /* Genode includes */
 #include <base/rpc_server.h>
+#include <dataspace/client.h>
 
 namespace Noux {
 

ports/src/noux/dir_file_system.h

@@ -20,14 +20,8 @@
 
 /* Noux includes */
 #include <noux_session/sysio.h>
-#include <tar_file_system.h>
+#include <file_system_registry.h>
-#include <fs_file_system.h>
+#include <vfs_handle.h>
-#include <terminal_file_system.h>
-#include <null_file_system.h>
-#include <zero_file_system.h>
-#include <stdio_file_system.h>
-#include <random_file_system.h>
-#include <block_file_system.h>
 
 
 namespace Noux {
@@ -69,7 +63,9 @@ namespace Noux {
 
 		public:
 
-			Dir_file_system(Xml_node node) : _first_file_system(0)
+			Dir_file_system(Xml_node node, File_system_registry &fs_registry)
+			:
+				_first_file_system(0)
 			{
 				/* remember directory name */
 				if (node.has_type("fstab"))
@@ -81,59 +77,22 @@ namespace Noux {
 
 					Xml_node sub_node = node.sub_node(i);
 
-					if (sub_node.has_type("tar")) {
-						_append_file_system(new Tar_file_system(sub_node));
-						continue;
-					}
-
-					if (sub_node.has_type("fs")) {
-						_append_file_system(new Fs_file_system(sub_node));
-						continue;
-					}
-
 					/* traverse into <dir> nodes */
 					if (sub_node.has_type("dir")) {
-						_append_file_system(new Dir_file_system(sub_node));
+						_append_file_system(new Dir_file_system(sub_node,
+						                                        fs_registry));
 						continue;
 					}
 
-					if (sub_node.has_type("terminal")) {
+					File_system_registry::Entry *fs = fs_registry.lookup(sub_node);
-						_append_file_system(new Terminal_file_system(sub_node));
+					if (fs) {
+						_append_file_system(fs->create(sub_node));
 						continue;
 					}
 
-					if (sub_node.has_type("null")) {
+					char type_name[64];
-						_append_file_system(new Null_file_system());
+					sub_node.type_name(type_name, sizeof(type_name));
-
+					PWRN("unknown fstab node type <%s>", type_name);
-						continue;
-					}
-
-					if (sub_node.has_type("zero")) {
-						_append_file_system(new Zero_file_system());
-
-						continue;
-					}
-
-					if (sub_node.has_type("stdio")) {
-						_append_file_system(new Stdio_file_system(sub_node));
-						continue;
-					}
-
-					if (sub_node.has_type("random")) {
-						_append_file_system(new Random_file_system(0, 0));
-						continue;
-					}
-
-					if (sub_node.has_type("block")) {
-						_append_file_system(new Block_file_system(sub_node));
-						continue;
-					}
-
-					{
-						char type_name[64];
-						sub_node.type_name(type_name, sizeof(type_name));
-						PWRN("unknown fstab node type <%s>", type_name);
-					}
 				}
 			}
 
@@ -660,26 +619,11 @@ namespace Noux {
 
 			/**
 			 * Synchronize all file systems
-			 *
-			 * Only file system using the File_system_session interface are
-			 * synchronized.
 			 */
 			void sync()
 			{
-				for (File_system *fs = _first_file_system; fs; fs = fs->next) {
+				for (File_system *fs = _first_file_system; fs; fs = fs->next)
-					Fs_file_system *fs_fs = dynamic_cast<Fs_file_system *>(fs);
+					fs->sync();
-					if (fs_fs) {
-						fs_fs->sync();
-						continue;
-					}
-
-					/* the directory might contain Fs_file_systems */
-					Dir_file_system *dir_fs = dynamic_cast<Dir_file_system *>(fs);
-					if (dir_fs) {
-						dir_fs->sync();
-						continue;
-					}
-				}
 			}
 
 

ports/src/noux/file_system.h

@@ -36,13 +36,6 @@ namespace Noux {
 
 		File_system() : next(0) { }
 
-		/**
-		 * Return name of file system
-		 *
-		 * This function is used for debugging only.
-		 */
-		virtual char const *name() const = 0;
-
 		/**
 		 * Synchronize file system
 		 *

ports/src/noux/file_system_registry.h

@@ -0,0 +1,55 @@
+/*
+ * \brief  Registry of file systems
+ * \author Norman Feske
+ * \date   2014-04-07
+ */
+
+/*
+ * Copyright (C) 2014 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 _NOUX__FILE_SYSTEM_REGISTRY_H_
+#define _NOUX__FILE_SYSTEM_REGISTRY_H_
+
+/* Noux includes */
+#include <file_system.h>
+
+namespace Noux {
+
+	class File_system_registry
+	{
+		public:
+
+			struct Entry : List<Entry>::Element
+			{
+				virtual File_system *create(Xml_node node) = 0;
+
+				virtual bool matches(Xml_node node) = 0;
+			};
+
+		private:
+
+			List<Entry> _list;
+
+		public:
+
+			void insert(Entry &entry)
+			{
+				_list.insert(&entry);
+			}
+
+			Entry *lookup(Xml_node node)
+			{
+				for (Entry *e = _list.first(); e; e = e->next())
+					if (e->matches(node))
+						return e;
+
+				return 0;
+			}
+	};
+}
+
+#endif /* _NOUX__FILE_SYSTEM_REGISTRY_H_ */

ports/src/noux/fs_file_system.h

@@ -574,7 +574,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "fs"; }
+			static char const *name() { return "fs"; }
 
 			void sync()
 			{

ports/src/noux/main.cc

@@ -30,6 +30,17 @@
 #include <io_receptor_registry.h>
 #include <destruct_queue.h>
 #include <kill_broadcaster.h>
+#include <file_system_registry.h>
+
+/* supported file systems */
+#include <tar_file_system.h>
+#include <fs_file_system.h>
+#include <terminal_file_system.h>
+#include <null_file_system.h>
+#include <zero_file_system.h>
+#include <stdio_file_system.h>
+#include <random_file_system.h>
+#include <block_file_system.h>
 
 
 static const bool verbose_quota  = false;
@@ -993,6 +1004,23 @@ void *operator new (Genode::size_t size) {
 	return Genode::env()->heap()->alloc(size); }
 
 
+template <typename FILE_SYSTEM>
+struct File_system_factory : Noux::File_system_registry::Entry
+{
+	Noux::File_system *create(Genode::Xml_node node) override
+	{
+		return new FILE_SYSTEM(node);
+	}
+
+	bool matches(Genode::Xml_node node) override
+	{
+		char buf[100];
+		node.type_name(buf, sizeof(buf));
+		return node.has_type(FILE_SYSTEM::name());
+	}
+};
+
+
 int main(int argc, char **argv)
 {
 	using namespace Noux;
@@ -1017,9 +1045,20 @@ int main(int argc, char **argv)
 		verbose = config()->xml_node().attribute("verbose").has_value("yes");
 	} catch (Xml_node::Nonexistent_attribute) { }
 
+	/* register file systems */
+	static File_system_registry fs_registry;
+	fs_registry.insert(*new File_system_factory<Tar_file_system>());
+	fs_registry.insert(*new File_system_factory<Fs_file_system>());
+	fs_registry.insert(*new File_system_factory<Terminal_file_system>());
+	fs_registry.insert(*new File_system_factory<Null_file_system>());
+	fs_registry.insert(*new File_system_factory<Zero_file_system>());
+	fs_registry.insert(*new File_system_factory<Stdio_file_system>());
+	fs_registry.insert(*new File_system_factory<Random_file_system>());
+	fs_registry.insert(*new File_system_factory<Block_file_system>());
+
 	/* initialize virtual file system */
 	static Dir_file_system
-		root_dir(config()->xml_node().sub_node("fstab"));
+		root_dir(config()->xml_node().sub_node("fstab"), fs_registry);
 
 	/* set user information */
 	try {

ports/src/noux/null_file_system.h

@@ -44,7 +44,7 @@ namespace Noux {
 
 		public:
 
-			Null_file_system() { }
+			Null_file_system(Xml_node) { }
 
 
 			/*********************************
@@ -162,7 +162,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "null"; }
+			static char const *name() { return "null"; }
 
 
 			/********************************

ports/src/noux/random_file_system.h

@@ -250,8 +250,10 @@ namespace Noux {
 
 		public:
 
-			Random_file_system(void *bytes, size_t nbytes)
+			Random_file_system(Xml_node node)
 			{
+				void   *bytes = 0;
+				size_t nbytes = 0;
 				_arc4random = new (env()->heap()) Arc4random(bytes, nbytes);
 			}
 
@@ -376,7 +378,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "random"; }
+			static char const *name() { return "random"; }
 
 
 			/********************************

ports/src/noux/stdio_file_system.h

@@ -179,7 +179,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "stdio"; }
+			static char const *name() { return "stdio"; }
 
 
 			/********************************

ports/src/noux/tar_file_system.h

@@ -606,7 +606,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "tar"; }
+			static char const *name() { return "tar"; }
 
 
 			/********************************

ports/src/noux/terminal_file_system.h

@@ -190,7 +190,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "terminal"; }
+			static char const *name() { return "terminal"; }
 
 
 			/********************************

ports/src/noux/zero_file_system.h

@@ -44,7 +44,7 @@ namespace Noux {
 
 		public:
 
-			Zero_file_system() { }
+			Zero_file_system(Xml_node) { }
 
 
 			/*********************************
@@ -162,7 +162,7 @@ namespace Noux {
 			 ** File_system interface **
 			 ***************************/
 
-			char const *name() const { return "zero"; }
+			static char const *name() { return "zero"; }
 
 
 			/********************************