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| -rw-r--r-- | src/storage/CompositeStorage.hxx | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/src/storage/CompositeStorage.hxx b/src/storage/CompositeStorage.hxx new file mode 100644 index 000000000..c3695c79d --- /dev/null +++ b/src/storage/CompositeStorage.hxx @@ -0,0 +1,166 @@ +/* + * 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 |