CompositeStorage: new Storage implementation

This is the backend for the upcoming "mount" command.

1 files changed, 123 insertions, 0 deletions

diff --git a/src/storage/CompositeStorage.hxx b/src/storage/CompositeStorage.hxx
new file mode 100644
index 000000000..696ffff61
--- /dev/null
+++ b/src/storage/CompositeStorage.hxx
@@ -0,0 +1,123 @@
+/*
+ * 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_COMPOSITE_STORAGE_HXX
+#define MPD_COMPOSITE_STORAGE_HXX
+
+#include "check.h"
+#include "StorageInterface.hxx"
+#include "thread/Mutex.hxx"
+#include "Compiler.h"
+
+#include <string>
+#include <map>
+
+class Error;
+class Storage;
+
+/**
+ * A #Storage implementation that combines multiple other #Storage
+ * instances in one virtual tree.  It is used to "mount" new #Storage
+ * instances into the storage tree.
+ *
+ * This class is thread-safe: mounts may be added and removed at any
+ * time in any thread.
+ */
+class CompositeStorage final : public Storage {
+	/**
+	 * A node in the virtual directory tree.
+	 */
+	struct Directory {
+		/**
+		 * The #Storage mounted n this virtual directory.  All
+		 * "leaf" Directory instances must have a #Storage.
+		 * Other Directory instances may have one, and child
+		 * mounts will be "mixed" in.
+		 */
+		Storage *storage;
+
+		std::map<std::string, Directory> children;
+
+		Directory():storage(nullptr) {}
+		~Directory();
+
+		gcc_pure
+		bool IsEmpty() const {
+			return storage == nullptr && children.empty();
+		}
+
+		gcc_pure
+		const Directory *Find(const char *uri) const;
+
+		Directory &Make(const char *uri);
+
+		bool Unmount();
+		bool Unmount(const char *uri);
+
+		gcc_pure
+		bool MapToRelativeUTF8(std::string &buffer,
+				       const char *uri) const;
+	};
+
+	struct FindResult {
+		const Directory *directory;
+		const char *uri;
+	};
+
+	/**
+	 * Protects the virtual #Directory tree.
+	 *
+	 * TODO: use readers-writer lock
+	 */
+	mutable Mutex mutex;
+
+	Directory root;
+
+	mutable std::string relative_buffer;
+
+public:
+	CompositeStorage();
+	virtual ~CompositeStorage();
+
+	void Mount(const char *uri, Storage *storage);
+	bool Unmount(const char *uri);
+
+	/* virtual methods from class Storage */
+	virtual bool GetInfo(const char *uri, bool follow, FileInfo &info,
+			     Error &error) override;
+
+	virtual StorageDirectoryReader *OpenDirectory(const char *uri,
+						      Error &error) override;
+
+	virtual std::string MapUTF8(const char *uri) const override;
+
+	virtual AllocatedPath MapFS(const char *uri) const override;
+
+	virtual const char *MapToRelativeUTF8(const char *uri) const override;
+
+private:
+	gcc_pure
+	FindResult FindStorage(const char *uri) const;
+	FindResult FindStorage(const char *uri, Error &error) const;
+
+	const char *MapToRelativeUTF8(const Directory &directory,
+				      const char *uri) const;
+};
+
+#endif