/* * Copyright 2003-2021 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_REMOTE_TAG_CACHE_HXX #define MPD_REMOTE_TAG_CACHE_HXX #include "input/RemoteTagScanner.hxx" #include "tag/Tag.hxx" #include "event/InjectEvent.hxx" #include "thread/Mutex.hxx" #include #include #include class RemoteTagCacheHandler; /** * A cache for tags received via #RemoteTagScanner. */ class RemoteTagCache final { static constexpr size_t MAX_SIZE = 4096; RemoteTagCacheHandler &handler; InjectEvent defer_invoke_handler; Mutex mutex; struct Item final : public boost::intrusive::unordered_set_base_hook>, public boost::intrusive::list_base_hook>, RemoteTagHandler { RemoteTagCache &parent; const std::string uri; std::unique_ptr scanner; Tag tag; template Item(RemoteTagCache &_parent, U &&_uri) noexcept :parent(_parent), uri(std::forward(_uri)) {} /* virtual methods from RemoteTagHandler */ void OnRemoteTag(Tag &&tag) noexcept override; void OnRemoteTagError(std::exception_ptr e) noexcept override; struct Hash : std::hash { using std::hash::operator(); gcc_pure std::size_t operator()(const Item &item) const noexcept { return std::hash::operator()(item.uri); } }; struct Equal { gcc_pure bool operator()(const Item &a, const Item &b) const noexcept { return a.uri == b.uri; } gcc_pure bool operator()(const std::string &a, const Item &b) const noexcept { return a == b.uri; } }; }; typedef boost::intrusive::list> ItemList; /** * These items have been resolved completely (successful or * failed). All callbacks have been invoked. The oldest * comes first in the list, and is the first one to be evicted * if the cache is full. */ ItemList idle_list; /** * A #RemoteTagScanner instances is currently busy on fetching * information, and we're waiting for our #RemoteTagHandler * methods to be invoked. */ ItemList waiting_list; /** * These items have just been resolved, and the * #RemoteTagCacheHandler is about to be invoked. After that, * they will be moved to the #idle_list. */ ItemList invoke_list; typedef boost::intrusive::unordered_set, boost::intrusive::equal, boost::intrusive::constant_time_size> KeyMap; std::array buckets; KeyMap map; public: RemoteTagCache(EventLoop &event_loop, RemoteTagCacheHandler &_handler) noexcept; ~RemoteTagCache() noexcept; void Lookup(const std::string &uri) noexcept; private: void InvokeHandlers() noexcept; void ScheduleInvokeHandlers() noexcept { defer_invoke_handler.Schedule(); } void ItemResolved(Item &item) noexcept; }; #endif