storage: add abstract interface

Prepare for the plugin interface.

src/storage/LocalStorage.cxx

@@ -81,14 +81,6 @@ LocalStorage::MapFS(const char *uri_utf8) const
 	return MapFS(uri_utf8, IgnoreError());
 }
 
-AllocatedPath
-LocalStorage::MapChildFS(const char *uri_utf8,
-			 const char *child_utf8) const
-{
-	const auto uri2 = PathTraitsUTF8::Build(uri_utf8, child_utf8);
-	return MapFS(uri2.c_str());
-}
-
 bool
 LocalStorage::GetInfo(const char *uri_utf8, bool follow, FileInfo &info,
 		      Error &error)

src/storage/LocalStorage.hxx

@@ -21,14 +21,13 @@
 #define MPD_STORAGE_LOCAL_HXX
 
 #include "check.h"
+#include "StorageInterface.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "fs/DirectoryReader.hxx"
 
 #include <string>
 
-struct FileInfo;
-
-class LocalDirectoryReader {
+class LocalDirectoryReader final : public StorageDirectoryReader {
 	AllocatedPath base_fs;
 
 	DirectoryReader reader;
@@ -43,12 +42,13 @@ public:
 		return reader.HasFailed();
 	}
 
-	const char *Read();
-
-	bool GetInfo(bool follow, FileInfo &info, Error &error);
+	/* virtual methods from class StorageDirectoryReader */
+	virtual const char *Read() override;
+	virtual bool GetInfo(bool follow, FileInfo &info,
+			     Error &error) override;
 };
 
-class LocalStorage {
+class LocalStorage final : public Storage {
 	const std::string base_utf8;
 	const AllocatedPath base_fs;
 
@@ -58,29 +58,16 @@ public:
 
 	LocalStorage(const LocalStorage &) = delete;
 
-	bool GetInfo(const char *uri_utf8, bool follow, FileInfo &info,
-		     Error &error);
+	/* virtual methods from class Storage */
+	virtual bool GetInfo(const char *uri_utf8, bool follow, FileInfo &info,
+			     Error &error) override;
 
-	LocalDirectoryReader *OpenDirectory(const char *uri_utf8,
-					    Error &error);
+	virtual LocalDirectoryReader *OpenDirectory(const char *uri_utf8,
+						    Error &error) override;
 
-	/**
-	 * Map the given relative URI to an absolute URI.
-	 */
-	gcc_pure
-	std::string MapUTF8(const char *uri_utf8) const;
+	virtual std::string MapUTF8(const char *uri_utf8) const override;
 
-	/**
-	 * 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
-	AllocatedPath MapFS(const char *uri_utf8) const;
-
-	gcc_pure
-	AllocatedPath MapChildFS(const char *uri_utf8,
-				 const char *child_utf8) const;
+	virtual AllocatedPath MapFS(const char *uri_utf8) const override;
 
 private:
 	AllocatedPath MapFS(const char *uri_utf8, Error &error) const;

src/storage/StorageInterface.cxx

@@ -0,0 +1,37 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "StorageInterface.hxx"
+#include "fs/AllocatedPath.hxx"
+#include "fs/Traits.hxx"
+
+AllocatedPath
+Storage::MapFS(gcc_unused const char *uri_utf8) const
+{
+	return AllocatedPath::Null();
+}
+
+AllocatedPath
+Storage::MapChildFS(const char *uri_utf8,
+		    const char *child_utf8) const
+{
+	const auto uri2 = PathTraitsUTF8::Build(uri_utf8, child_utf8);
+	return MapFS(uri2.c_str());
+}

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