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