mirror of https://github.com/TomHarte/CLK.git
109 lines
3.8 KiB
C++
109 lines
3.8 KiB
C++
//
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// TimedEventLoop.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 29/07/2016.
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// Copyright 2016 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include "Storage.hpp"
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#include "../ClockReceiver/ClockReceiver.hpp"
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#include "../SignalProcessing/Stepper.hpp"
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#include <memory>
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namespace Storage {
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/*!
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Provides a mechanism for arbitrarily timed events to be processed according to a fixed-base
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discrete clock signal, ensuring correct timing.
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Subclasses are responsible for calling @c set_next_event_time_interval to establish the time
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until a next event; @c process_next_event will be called when that event occurs, with progression
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determined via @c run_for.
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Due to the aggregation of total timing information between events, e.g. if an event loop has
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a clock rate of 1000 ticks per second and a steady stream of events that occur 10,000 times a second,
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bookkeeping is necessary to ensure that 10 events are triggered per tick. Subclasses should call
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@c reset_timer if there is a discontinuity in events.
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Subclasses may also call @c jump_to_next_event to cause the next event to be communicated instantly.
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Subclasses are therefore expected to call @c set_next_event_time_interval upon obtaining an event stream,
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and again in response to each call to @c process_next_event while events are ongoing. They may use
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@c reset_timer to initiate a distinctly-timed stream or @c jump_to_next_event to short-circuit the timing
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loop and fast forward immediately to the next event.
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*/
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class TimedEventLoop {
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public:
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/*!
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Constructs a timed event loop that will be clocked at @c input_clock_rate.
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*/
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TimedEventLoop(Cycles::IntType input_clock_rate);
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/*!
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Advances the event loop by @c number_of_cycles cycles.
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*/
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void run_for(const Cycles cycles);
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/*!
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@returns the number of whole cycles remaining until the next event is triggered.
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*/
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Cycles::IntType get_cycles_until_next_event() const;
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/*!
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@returns the input clock rate.
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*/
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Cycles::IntType get_input_clock_rate() const;
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protected:
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/*!
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Sets the time interval, as a proportion of a second, until the next event should be triggered.
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*/
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void set_next_event_time_interval(Time interval);
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void set_next_event_time_interval(float interval);
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/*!
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Communicates that the next event is triggered. A subclass will idiomatically process that event
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and make a fresh call to @c set_next_event_time_interval to keep the event loop running.
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*/
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virtual void process_next_event() = 0;
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/*!
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Optionally allows a subclass to track time within run_for periods; if a subclass implements
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advnace then it will receive advance increments that add up to the number of cycles supplied
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to run_for, but calls to process_next_event will be precisely interspersed. No time will carry
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forward between calls into run_for; a subclass can receive arbitrarily many instructions to
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advance before receiving a process_next_event.
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*/
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virtual void advance([[maybe_unused]] const Cycles cycles) {};
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/*!
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Resets timing, throwing away any current internal state. So clears any fractional ticks
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that the event loop is currently tracking.
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*/
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void reset_timer();
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/*!
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Causes an immediate call to @c process_next_event and a call to @c reset_timer with the
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net effect of processing the current event immediately and fast forwarding exactly to the
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start of the interval prior to the next event.
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*/
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void jump_to_next_event();
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/*!
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@returns the amount of time that has passed since the last call to @c set_next_time_interval,
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which will always be less than or equal to the time that was supplied to @c set_next_time_interval.
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*/
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Time get_time_into_next_event();
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private:
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Cycles::IntType input_clock_rate_ = 0;
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Cycles::IntType cycles_until_event_ = 0;
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float subcycles_until_event_ = 0.0f;
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};
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}
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