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CLK/Concurrency/AsyncTaskQueue.hpp

96 lines
2.6 KiB
C++

//
// AsyncTaskQueue.hpp
// Clock Signal
//
// Created by Thomas Harte on 07/10/2016.
// Copyright © 2016 Thomas Harte. All rights reserved.
//
#ifndef AsyncTaskQueue_hpp
#define AsyncTaskQueue_hpp
#include <atomic>
#include <condition_variable>
#include <functional>
#include <list>
#include <memory>
#include <thread>
#ifdef __APPLE__
#include <dispatch/dispatch.h>
#endif
namespace Concurrency {
/*!
An async task queue allows a caller to enqueue void(void) functions. Those functions are guaranteed
to be performed serially and asynchronously from the caller. A caller may also request to flush,
causing it to block until all previously-enqueued functions are complete.
*/
class AsyncTaskQueue {
public:
AsyncTaskQueue();
~AsyncTaskQueue();
/*!
Adds @c function to the queue.
@discussion Functions will be performed serially and asynchronously. This method is safe to
call from multiple threads.
@parameter function The function to enqueue.
*/
void enqueue(std::function<void(void)> function);
/*!
Blocks the caller until all previously-enqueud functions have completed.
*/
void flush();
private:
#ifdef __APPLE__
dispatch_queue_t serial_dispatch_queue_;
#else
std::unique_ptr<std::thread> thread_;
std::mutex queue_mutex_;
std::list<std::function<void(void)>> pending_tasks_;
std::condition_variable processing_condition_;
std::atomic_bool should_destruct_;
#endif
};
/*!
A deferring async task queue is one that accepts a list of functions to be performed but defers
any action until told to perform. It performs them by enquing a single asynchronous task that will
perform the deferred tasks in order.
It therefore offers similar semantics to an asynchronous task queue, but allows for management of
synchronisation costs, since neither defer nor perform make any effort to be thread safe.
*/
class DeferringAsyncTaskQueue: public AsyncTaskQueue {
public:
/*!
Adds a function to the deferral list.
This is not thread safe; it should be serialised with other calls to itself and to perform.
*/
void defer(std::function<void(void)> function);
/*!
Enqueues a function that will perform all currently deferred functions, in the
order that they were deferred.
This is not thread safe; it should be serialised with other calls to itself and to defer.
*/
void perform();
private:
// TODO: this is a shared_ptr because of the issues capturing moveables in C++11;
// switch to a unique_ptr if/when adapting to C++14
std::shared_ptr<std::list<std::function<void(void)>>> deferred_tasks_;
};
}
#endif /* Concurrency_hpp */