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CLK/Concurrency/BestEffortUpdater.cpp

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//
// BestEffortUpdater.cpp
// Clock Signal
//
// Created by Thomas Harte on 04/10/2017.
// Copyright © 2017 Thomas Harte. All rights reserved.
//
#include "BestEffortUpdater.hpp"
#include <cmath>
using namespace Concurrency;
void BestEffortUpdater::update() {
// Perform an update only if one is not currently ongoing.
if(!update_is_ongoing_.test_and_set()) {
async_task_queue_.enqueue([this]() {
// Get time now using the highest-resolution clock provided by the implementation, and determine
// the duration since the last time this section was entered.
const std::chrono::time_point<std::chrono::high_resolution_clock> now = std::chrono::high_resolution_clock::now();
const auto elapsed = now - previous_time_point_;
previous_time_point_ = now;
if(has_previous_time_point_) {
// If the duration is valid, convert it to integer cycles, maintaining a rolling error and call the delegate
// if there is one. Proceed only if the number of cycles is positive, and cap it to the per-second maximum —
// it's possible this is an adjustable clock so be ready to swallow unexpected adjustments.
const int64_t duration = std::chrono::duration_cast<std::chrono::nanoseconds>(elapsed).count();
if(duration > 0) {
double cycles = ((static_cast<double>(duration) * clock_rate_) / 1e9) + error_;
error_ = fmod(cycles, 1.0);
if(delegate_) {
delegate_->update(this, static_cast<int>(std::min(cycles, clock_rate_)), has_skipped_);
}
has_skipped_ = false;
}
} else {
has_previous_time_point_ = true;
}
// Allow furthers updates to occur.
update_is_ongoing_.clear();
});
} else {
async_task_queue_.enqueue([this]() {
has_skipped_ = true;
});
}
}
void BestEffortUpdater::flush() {
async_task_queue_.flush();
}
void BestEffortUpdater::set_delegate(Delegate *const delegate) {
async_task_queue_.enqueue([this, delegate]() {
delegate_ = delegate;
});
}
void BestEffortUpdater::set_clock_rate(const double clock_rate) {
async_task_queue_.enqueue([this, clock_rate]() {
this->clock_rate_ = clock_rate;
});
}