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83 lines
2.2 KiB
C++
83 lines
2.2 KiB
C++
//
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// BestEffortUpdater.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 04/10/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#ifndef BestEffortUpdater_hpp
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#define BestEffortUpdater_hpp
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#include <atomic>
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#include <chrono>
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#include <condition_variable>
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#include <mutex>
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#include <thread>
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#include "../ClockReceiver/TimeTypes.hpp"
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namespace Concurrency {
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/*!
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Accepts timing cues from multiple threads and ensures that a delegate receives calls to total
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a certain number of cycles per second, that those calls are strictly serialised, and that no
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backlog of calls accrues.
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No guarantees about the thread that the delegate will be called on are made.
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*/
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class BestEffortUpdater {
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public:
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BestEffortUpdater();
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~BestEffortUpdater();
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/// A delegate receives timing cues.
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struct Delegate {
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/*!
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Instructs the delegate to run for at least @c duration, providing hints as to whether multiple updates were requested before the previous had completed
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(as @c did_skip_previous_update) and providing the union of any flags supplied to @c update.
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@returns The amount of time actually run for.
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*/
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virtual Time::Seconds update(BestEffortUpdater *updater, Time::Seconds duration, bool did_skip_previous_update, int flags) = 0;
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};
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/// Sets the current delegate.
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void set_delegate(Delegate *);
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/*!
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If the delegate is not currently in the process of an `update` call, calls it now to catch up to the current time.
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The call is asynchronous; this method will return immediately.
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*/
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void update(int flags = 0);
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/// Blocks until any ongoing update is complete; may spin.
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void flush();
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private:
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std::atomic<bool> should_quit_;
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std::atomic<bool> is_updating_;
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int64_t target_time_;
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int flags_ = 0;
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bool update_requested_;
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std::mutex update_mutex_;
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std::condition_variable update_condition_;
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decltype(target_time_) previous_time_point_;
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bool has_previous_time_point_ = false;
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std::atomic<bool> has_skipped_ = false;
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std::atomic<Delegate *>delegate_ = nullptr;
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void update_loop();
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// This is deliberately at the bottom, to ensure it constructs after the various
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// mutexs, conditions, etc, that it'll depend upon.
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std::thread update_thread_;
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};
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}
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#endif /* BestEffortUpdater_hpp */
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