110 lines
2.5 KiB
C++
110 lines
2.5 KiB
C++
// SPDX-License-Identifier: GPL-2.0-or-later
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// Copyright The Music Player Daemon Project
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#pragma once
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#include "input/RemoteTagScanner.hxx"
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#include "tag/Tag.hxx"
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#include "event/InjectEvent.hxx"
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#include "thread/Mutex.hxx"
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#include "util/IntrusiveList.hxx"
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#include "util/IntrusiveHashSet.hxx"
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#include <array>
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#include <functional>
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#include <memory>
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#include <string>
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#include <utility>
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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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InjectEvent defer_invoke_handler;
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Mutex mutex;
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struct Item final
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: public IntrusiveHashSetHook<>,
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public IntrusiveListHook<>,
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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 GetUri {
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[[gnu::pure]]
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std::string_view operator()(const Item &item) const noexcept {
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return item.uri;
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}
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};
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};
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using ItemList = IntrusiveList<Item>;
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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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IntrusiveHashSet<
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Item, 127,
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IntrusiveHashSetOperators<Item, Item::GetUri,
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std::hash<std::string_view>,
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std::equal_to<std::string_view>>,
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IntrusiveHashSetBaseHookTraits<Item>,
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IntrusiveHashSetOptions{.constant_time_size = true}> 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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