69 lines
1.4 KiB
C++
69 lines
1.4 KiB
C++
/*
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This file is part of Telegram Desktop,
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the official desktop application for the Telegram messaging service.
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For license and copyright information please follow this link:
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https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
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*/
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#pragma once
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#include <list>
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#include <unordered_map>
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namespace base {
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template <typename Entry>
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class last_used_cache {
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public:
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void up(Entry entry);
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void remove(Entry entry);
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void clear();
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Entry take_lowest();
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private:
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std::list<Entry> _queue;
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std::unordered_map<Entry, typename std::list<Entry>::iterator> _map;
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};
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template <typename Entry>
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void last_used_cache<Entry>::up(Entry entry) {
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if (!_queue.empty() && _queue.back() == entry) {
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return;
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}
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const auto i = _map.find(entry);
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if (i != end(_map)) {
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_queue.splice(end(_queue), _queue, i->second);
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} else {
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_map.emplace(entry, _queue.insert(end(_queue), entry));
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}
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}
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template <typename Entry>
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void last_used_cache<Entry>::remove(Entry entry) {
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const auto i = _map.find(entry);
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if (i != end(_map)) {
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_queue.erase(i->second);
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_map.erase(i);
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}
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}
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template <typename Entry>
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void last_used_cache<Entry>::clear() {
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_queue.clear();
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_map.clear();
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}
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template <typename Entry>
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Entry last_used_cache<Entry>::take_lowest() {
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if (_queue.empty()) {
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return Entry();
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}
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auto result = std::move(_queue.front());
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_queue.erase(begin(_queue));
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_map.erase(result);
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return result;
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}
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} // namespace base
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