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+/*
+ * 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();
+
+ /**
+ * Get the #Storage at the specified mount point. Returns
+ * nullptr if the given URI is not a mount point.
+ *
+ * The returned pointer is unprotected. No other thread is
+ * allowed to unmount the given mount point while the return
+ * value is being used.
+ */
+ gcc_pure gcc_nonnull_all
+ Storage *GetMount(const char *uri);
+
+ /**
+ * Call the given function for each mounted storage, including
+ * the root storage. Passes mount point URI and the a const
+ * Storage reference to the function.
+ */
+ template<typename T>
+ void VisitMounts(T t) const {
+ const ScopeLock protect(mutex);
+ std::string uri;
+ VisitMounts(uri, root, t);
+ }
+
+ void Mount(const char *uri, Storage *storage);
+ bool Unmount(const char *uri);
+
+ /* virtual methods from class Storage */
+ bool GetInfo(const char *uri, bool follow, FileInfo &info,
+ Error &error) override;
+
+ StorageDirectoryReader *OpenDirectory(const char *uri,
+ Error &error) override;
+
+ std::string MapUTF8(const char *uri) const override;
+
+ AllocatedPath MapFS(const char *uri) const override;
+
+ const char *MapToRelativeUTF8(const char *uri) const override;
+
+private:
+ template<typename T>
+ void VisitMounts(std::string &uri, const Directory &directory,
+ T t) const {
+ const Storage *const storage = directory.storage;
+ if (storage != nullptr)
+ t(uri.c_str(), *storage);
+
+ if (!uri.empty())
+ uri.push_back('/');
+
+ const size_t uri_length = uri.length();
+
+ for (const auto &i : directory.children) {
+ uri.resize(uri_length);
+ uri.append(i.first);
+
+ VisitMounts(uri, i.second, t);
+ }
+ }
+
+ 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