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67 lines
1.6 KiB
C++
67 lines
1.6 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 "AsyncTaskQueue.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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virtual void update(BestEffortUpdater *updater, int cycles, bool did_skip_previous_update) = 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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/// Sets the clock rate of the delegate.
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void set_clock_rate(double clock_rate);
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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();
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/// Blocks until any ongoing update is complete.
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void flush();
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private:
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std::atomic_flag update_is_ongoing_;
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AsyncTaskQueue async_task_queue_;
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std::chrono::time_point<std::chrono::high_resolution_clock> previous_time_point_;
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bool has_previous_time_point_ = false;
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double error_ = 0.0;
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bool has_skipped_ = false;
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Delegate *delegate_ = nullptr;
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double clock_rate_ = 1.0;
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};
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}
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#endif /* BestEffortUpdater_hpp */
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