💿🐜 Antkeeper source code
https://antkeeper.com
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143 lines
3.5 KiB
143 lines
3.5 KiB
/*
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* Copyright (C) 2023 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code 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 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code 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
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_EVENT_QUEUE_HPP
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#define ANTKEEPER_EVENT_QUEUE_HPP
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#include "event/subscriber.hpp"
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#include "event/subscription.hpp"
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#include <any>
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#include <functional>
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#include <list>
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#include <map>
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#include <memory>
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#include <typeindex>
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#include <utility>
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namespace event {
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/**
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* Collects messages from publishers to be distributed to subscribers when desired.
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*/
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class queue
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{
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public:
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/**
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* Subscribes a function object to messages published by this queue.
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*
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* @tparam T Message type.
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*
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* @param subscriber Function object to subscribe.
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*
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* @return Shared subscription object which will unsubscribe the subscriber on destruction.
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*/
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template <class T>
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[[nodiscard]] std::shared_ptr<subscription> subscribe(subscriber<T>&& subscriber)
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{
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// Allocate shared pointer to std::any object containing subscriber
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std::shared_ptr<std::any> shared_subscriber = std::make_shared<std::any>(std::make_any<event::subscriber<T>>(std::move(subscriber)));
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// Append subscriber to subscriber list and store iterator
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auto iterator = subscribers.emplace(std::type_index(typeid(T)), shared_subscriber);
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// Construct and return a shared subscription object which removes the subscriber from the subscriber list when unsubscribed or destructed
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return std::make_shared<subscription>
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(
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std::static_pointer_cast<void>(shared_subscriber),
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[this, iterator = std::move(iterator)]()
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{
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this->subscribers.erase(iterator);
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}
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);
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}
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/**
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* Adds a message to the queue, to be distributed later.
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*
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* @tparam T Message type.
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*
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* @param message Message to enqueue.
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*/
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template <class T>
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void enqueue(const T& message)
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{
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messages.emplace_back
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(
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[this, message]()
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{
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this->distribute<T>(message);
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}
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);
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}
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/**
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* Distributes queued messages in FIFO order to subscribers.
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*/
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void flush()
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{
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while (!messages.empty())
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{
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messages.front()();
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messages.pop_front();
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}
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}
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/**
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* Removes all messages from the queue.
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*/
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void clear()
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{
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messages.clear();
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}
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/**
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* Returns `true` if there are no messages in the queue, `false` otherwise.
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*/
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[[nodiscard]] inline bool empty() const noexcept
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{
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return messages.empty();
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}
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private:
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/**
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* Distributes a message.
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*
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* @tparam T Message type.
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*
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* @param message Message to distribute.
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*/
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template <class T>
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void distribute(const T& message) const
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{
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// For each subscriber of the given message type
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const auto range = subscribers.equal_range(std::type_index(typeid(T)));
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for (auto i = range.first; i != range.second; ++i)
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{
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// Send message to subscriber
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std::any_cast<subscriber<T>>(*(i->second))(message);
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}
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}
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std::multimap<std::type_index, std::shared_ptr<std::any>> subscribers;
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std::list<std::function<void()>> messages;
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};
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} // namespace event
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#endif // ANTKEEPER_EVENT_QUEUE_HPP
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