storage: add abstract interface

Prepare for the plugin interface.

src/storage/StorageInterface.hxx

@@ -0,0 +1,69 @@
+/*
+ * 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_STORAGE_INTERFACE_HXX
+#define MPD_STORAGE_INTERFACE_HXX
+
+#include "check.h"
+#include "fs/AllocatedPath.hxx"
+#include "fs/DirectoryReader.hxx"
+
+#include <string>
+
+struct FileInfo;
+class AllocatedPath;
+
+class StorageDirectoryReader {
+public:
+	virtual ~StorageDirectoryReader() {}
+
+	virtual const char *Read() = 0;
+	virtual bool GetInfo(bool follow, FileInfo &info, Error &error) = 0;
+};
+
+class Storage {
+public:
+	virtual ~Storage() {}
+
+	virtual bool GetInfo(const char *uri_utf8, bool follow, FileInfo &info,
+			     Error &error) = 0;
+
+	virtual StorageDirectoryReader *OpenDirectory(const char *uri_utf8,
+						      Error &error) = 0;
+
+	/**
+	 * Map the given relative URI to an absolute URI.
+	 */
+	gcc_pure
+	virtual std::string MapUTF8(const char *uri_utf8) const = 0;
+
+	/**
+	 * Map the given relative URI to a local file path.  Returns
+	 * AllocatedPath::Null() on error or if this storage does not
+	 * support local files.
+	 */
+	gcc_pure
+	virtual AllocatedPath MapFS(const char *uri_utf8) const;
+
+	gcc_pure
+	AllocatedPath MapChildFS(const char *uri_utf8,
+				 const char *child_utf8) const;
+};
+
+#endif