db/simple: mount points

A SimpleDatabase instance can now "mount" other Database instances at
certain locations.  This is used to use a new SimpleDatabase instance
for each storage mount (issued with the "mount" protocol command).
Each such instance has its own database file, stored in the directory
that is specified with the "cache_directory" option.

src/db/plugins/simple/Mount.hxx

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_DB_SIMPLE_MOUNT_HXX
+#define MPD_DB_SIMPLE_MOUNT_HXX
+
+#include "db/Visitor.hxx"
+
+class Database;
+class SongFilter;
+class Error;
+
+bool
+WalkMount(const char *base, const Database &db,
+	  bool recursive, const SongFilter *filter,
+	  const VisitDirectory &visit_directory, const VisitSong &visit_song,
+	  const VisitPlaylist &visit_playlist,
+	  Error &error);
+
+#endif