144 lines
3.7 KiB
C++
144 lines
3.7 KiB
C++
/*
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* Copyright 2003-2020 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef MPD_REMOTE_TAG_CACHE_HXX
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#define MPD_REMOTE_TAG_CACHE_HXX
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#include "input/RemoteTagScanner.hxx"
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#include "tag/Tag.hxx"
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#include "event/DeferEvent.hxx"
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#include "thread/Mutex.hxx"
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#include <boost/intrusive/list.hpp>
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#include <boost/intrusive/unordered_set.hpp>
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#include <string>
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class RemoteTagCacheHandler;
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/**
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* A cache for tags received via #RemoteTagScanner.
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*/
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class RemoteTagCache final {
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static constexpr size_t MAX_SIZE = 4096;
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RemoteTagCacheHandler &handler;
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DeferEvent defer_invoke_handler;
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Mutex mutex;
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struct Item final
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: public boost::intrusive::unordered_set_base_hook<boost::intrusive::link_mode<boost::intrusive::normal_link>>,
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public boost::intrusive::list_base_hook<boost::intrusive::link_mode<boost::intrusive::normal_link>>,
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RemoteTagHandler
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{
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RemoteTagCache &parent;
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const std::string uri;
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std::unique_ptr<RemoteTagScanner> scanner;
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Tag tag;
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template<typename U>
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Item(RemoteTagCache &_parent, U &&_uri) noexcept
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:parent(_parent), uri(std::forward<U>(_uri)) {}
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/* virtual methods from RemoteTagHandler */
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void OnRemoteTag(Tag &&tag) noexcept override;
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void OnRemoteTagError(std::exception_ptr e) noexcept override;
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struct Hash : std::hash<std::string> {
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using std::hash<std::string>::operator();
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gcc_pure
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std::size_t operator()(const Item &item) const noexcept {
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return std::hash<std::string>::operator()(item.uri);
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}
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};
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struct Equal {
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gcc_pure
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bool operator()(const Item &a,
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const Item &b) const noexcept {
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return a.uri == b.uri;
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}
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gcc_pure
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bool operator()(const std::string &a,
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const Item &b) const noexcept {
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return a == b.uri;
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}
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};
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};
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typedef boost::intrusive::list<Item,
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boost::intrusive::constant_time_size<false>> ItemList;
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/**
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* These items have been resolved completely (successful or
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* failed). All callbacks have been invoked. The oldest
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* comes first in the list, and is the first one to be evicted
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* if the cache is full.
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*/
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ItemList idle_list;
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/**
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* A #RemoteTagScanner instances is currently busy on fetching
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* information, and we're waiting for our #RemoteTagHandler
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* methods to be invoked.
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*/
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ItemList waiting_list;
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/**
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* These items have just been resolved, and the
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* #RemoteTagCacheHandler is about to be invoked. After that,
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* they will be moved to the #idle_list.
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*/
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ItemList invoke_list;
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typedef boost::intrusive::unordered_set<Item,
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boost::intrusive::hash<Item::Hash>,
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boost::intrusive::equal<Item::Equal>,
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boost::intrusive::constant_time_size<true>> KeyMap;
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std::array<typename KeyMap::bucket_type, 127> buckets;
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KeyMap map;
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public:
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RemoteTagCache(EventLoop &event_loop,
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RemoteTagCacheHandler &_handler) noexcept;
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~RemoteTagCache() noexcept;
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void Lookup(const std::string &uri) noexcept;
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private:
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void InvokeHandlers() noexcept;
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void ScheduleInvokeHandlers() noexcept {
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defer_invoke_handler.Schedule();
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}
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void ItemResolved(Item &item) noexcept;
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};
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#endif
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