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Merge pull request #1039 from TomHarte/UniqueAsync

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Switch DeferringAsyncTaskQueue to `unique_ptr`.
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Thomas Harte 2022-06-02 17:06:59 -04:00 committed by GitHub
commit 103de74063
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2 changed files with 42 additions and 43 deletions
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37
Concurrency/AsyncTaskQueue.cpp
View File

@ -12,17 +12,13 @@ using namespace Concurrency;
AsyncTaskQueue::AsyncTaskQueue()
#ifndef USE_GCD
: should_destruct_(false)
#endif
{
#ifdef USE_GCD
serial_dispatch_queue_ = dispatch_queue_create("com.thomasharte.clocksignal.asyntaskqueue", DISPATCH_QUEUE_SERIAL);
#else
thread_ = std::make_unique<std::thread>([this]() {
:
should_destruct_(false),
thread_([this] () {
while(!should_destruct_) {
std::function<void(void)> next_function;
// Take lock, check for a new task
// Take lock, check for a new task.
std::unique_lock lock(queue_mutex_);
if(!pending_tasks_.empty()) {
next_function = pending_tasks_.front();
@ -30,29 +26,33 @@ AsyncTaskQueue::AsyncTaskQueue()
}
if(next_function) {
// If there is a task, release lock and perform it
// If there is a task, release lock and perform it.
lock.unlock();
next_function();
} else {
// If there isn't a task, atomically block on the processing condition and release the lock
// until there's something pending (and then release it again via scope)
// until there's something pending (and then release it again via scope).
processing_condition_.wait(lock);
}
}
});
})
#else
: serial_dispatch_queue_(dispatch_queue_create("com.thomasharte.clocksignal.asyntaskqueue", DISPATCH_QUEUE_SERIAL))
#endif
}
{}
AsyncTaskQueue::~AsyncTaskQueue() {
#ifdef USE_GCD
flush();
dispatch_release(serial_dispatch_queue_);
serial_dispatch_queue_ = nullptr;
#else
// Set should destruct, and then give the thread a bit of a nudge
// via an empty enqueue.
should_destruct_ = true;
enqueue([](){});
thread_->join();
thread_.reset();
// Wait for the thread safely to terminate.
thread_.join();
#endif
}
@ -88,16 +88,15 @@ DeferringAsyncTaskQueue::~DeferringAsyncTaskQueue() {
void DeferringAsyncTaskQueue::defer(std::function<void(void)> function) {
if(!deferred_tasks_) {
deferred_tasks_ = std::make_shared<std::list<std::function<void(void)>>>();
deferred_tasks_ = std::make_unique<TaskList>();
}
deferred_tasks_->push_back(function);
}
void DeferringAsyncTaskQueue::perform() {
if(!deferred_tasks_) return;
std::shared_ptr<std::list<std::function<void(void)>>> deferred_tasks = deferred_tasks_;
deferred_tasks_.reset();
enqueue([deferred_tasks] {
enqueue([deferred_tasks_raw = deferred_tasks_.release()] {
std::unique_ptr<TaskList> deferred_tasks(deferred_tasks_raw);
for(const auto &function : *deferred_tasks) {
function();
}

16
Concurrency/AsyncTaskQueue.hpp
View File

@ -23,6 +23,8 @@
namespace Concurrency {
using TaskList = std::list<std::function<void(void)>>;
/*!
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,
@ -51,12 +53,12 @@ class AsyncTaskQueue {
#ifdef USE_GCD
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_;
std::condition_variable processing_condition_;
std::mutex queue_mutex_;
TaskList pending_tasks_;
std::thread thread_;
#endif
};
@ -93,9 +95,7 @@ class DeferringAsyncTaskQueue: public AsyncTaskQueue {
void flush();
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_;
std::unique_ptr<TaskList> deferred_tasks_;
};
}