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Farewell, BestEffortUpdater.

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Thomas Harte 2020-05-09 21:48:04 -04:00
parent 4136428db3
commit 3729bddb2a
3 changed files with 0 additions and 190 deletions
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100
Concurrency/BestEffortUpdater.cpp
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@ -1,100 +0,0 @@
//
// 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;
BestEffortUpdater::BestEffortUpdater() :
update_thread_([this]() {
this->update_loop();
}) {}
BestEffortUpdater::~BestEffortUpdater() {
// Sever the delegate now, as soon as possible, then wait for any
// pending tasks to finish.
set_delegate(nullptr);
flush();
// Wind up the update thread.
should_quit_ = true;
update();
update_thread_.join();
}
void BestEffortUpdater::update(int flags) {
// Bump the requested target time and set the update requested flag.
{
std::lock_guard<decltype(update_mutex_)> lock(update_mutex_);
has_skipped_ = update_requested_;
update_requested_ = true;
flags_ |= flags;
target_time_ = std::chrono::high_resolution_clock::now().time_since_epoch().count();
}
update_condition_.notify_one();
}
void BestEffortUpdater::update_loop() {
while(true) {
std::unique_lock<decltype(update_mutex_)> lock(update_mutex_);
is_updating_ = false;
// Wait to be signalled.
update_condition_.wait(lock, [this]() -> bool {
return update_requested_;
});
// Possibly this signalling really means 'quit'.
if(should_quit_) return;
// Note update started, crib the target time.
auto target_time = target_time_;
update_requested_ = false;
// If this was actually the first update request, silently swallow it.
if(!has_previous_time_point_) {
has_previous_time_point_ = true;
previous_time_point_ = target_time;
continue;
}
// Release the lock on requesting new updates.
is_updating_ = true;
const int flags = flags_;
flags_ = 0;
lock.unlock();
// Invoke the delegate, if supplied, in order to run.
const int64_t integer_duration = std::max(target_time - previous_time_point_, int64_t(0));
const auto delegate = delegate_.load();
if(delegate) {
// Cap running at 1/5th of a second, to avoid doing a huge amount of work after any
// brief system interruption.
const double duration = std::min(double(integer_duration) / 1e9, 0.2);
const double elapsed_duration = delegate->update(this, duration, has_skipped_, flags);
previous_time_point_ += int64_t(elapsed_duration * 1e9);
has_skipped_ = false;
}
}
}
void BestEffortUpdater::flush() {
// Spin lock; this is allowed to be slow.
while(true) {
std::lock_guard<decltype(update_mutex_)> lock(update_mutex_);
if(!is_updating_) return;
}
}
void BestEffortUpdater::set_delegate(Delegate *const delegate) {
delegate_.store(delegate);
}

82
Concurrency/BestEffortUpdater.hpp
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@ -1,82 +0,0 @@
//
// BestEffortUpdater.hpp
// Clock Signal
//
// Created by Thomas Harte on 04/10/2017.
// Copyright 2017 Thomas Harte. All rights reserved.
//
#ifndef BestEffortUpdater_hpp
#define BestEffortUpdater_hpp
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <mutex>
#include <thread>
#include "../ClockReceiver/TimeTypes.hpp"
namespace Concurrency {
/*!
Accepts timing cues from multiple threads and ensures that a delegate receives calls to total
a certain number of cycles per second, that those calls are strictly serialised, and that no
backlog of calls accrues.
No guarantees about the thread that the delegate will be called on are made.
*/
class BestEffortUpdater {
public:
BestEffortUpdater();
~BestEffortUpdater();
/// A delegate receives timing cues.
struct Delegate {
/*!
Instructs the delegate to run for at least @c duration, providing hints as to whether multiple updates were requested before the previous had completed
(as @c did_skip_previous_update) and providing the union of any flags supplied to @c update.
@returns The amount of time actually run for.
*/
virtual Time::Seconds update(BestEffortUpdater *updater, Time::Seconds duration, bool did_skip_previous_update, int flags) = 0;
};
/// Sets the current delegate.
void set_delegate(Delegate *);
/*!
If the delegate is not currently in the process of an `update` call, calls it now to catch up to the current time.
The call is asynchronous; this method will return immediately.
*/
void update(int flags = 0);
/// Blocks until any ongoing update is complete; may spin.
void flush();
private:
std::atomic<bool> should_quit_;
std::atomic<bool> is_updating_;
int64_t target_time_;
int flags_ = 0;
bool update_requested_;
std::mutex update_mutex_;
std::condition_variable update_condition_;
decltype(target_time_) previous_time_point_;
bool has_previous_time_point_ = false;
std::atomic<bool> has_skipped_ = false;
std::atomic<Delegate *>delegate_ = nullptr;
void update_loop();
// This is deliberately at the bottom, to ensure it constructs after the various
// mutexs, conditions, etc, that it'll depend upon.
std::thread update_thread_;
};
}
#endif /* BestEffortUpdater_hpp */

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