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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#pragma once
#include <nanotrace/nanotracehr.h>
#include <condition_variable>
#include <deque>
#include <mutex>
#include <thread>
namespace QmlDesigner {
template<typename Task, typename DispatchCallback, typename ClearCallback>
class TaskQueue
{
using Tasks = std::deque<Task>;
public:
TaskQueue(DispatchCallback dispatchCallback, ClearCallback clearCallback)
: m_dispatchCallback(std::move(dispatchCallback))
, m_clearCallback(std::move(clearCallback))
{}
~TaskQueue() { destroy(); }
template<typename TraceEvent, NanotraceHR::Tracing isEnabled, typename... Arguments>
void addTask(NanotraceHR::Token<TraceEvent, isEnabled> traceToken, Arguments &&...arguments)
{
{
std::unique_lock lock{m_mutex};
ensureThreadIsRunning(lock, std::move(traceToken));
m_tasks.emplace_back(std::forward<Arguments>(arguments)...);
}
m_condition.notify_all();
}
template<typename... Arguments>
void addTask(Arguments &&...arguments)
{
addTask(NanotraceHR::DisabledToken{}, std::forward<Arguments>(arguments)...);
}
void clean()
{
Tasks oldTasks;
{
std::unique_lock lock{m_mutex};
std::swap(m_tasks, oldTasks);
}
clearTasks(oldTasks);
}
void putThreadToSleep()
{
{
std::unique_lock lock{m_mutex};
m_sleeping = true;
}
m_condition.notify_all();
}
private:
void destroy()
{
stopThread();
joinThread();
clearTasks(m_tasks);
}
[[nodiscard]] std::tuple<std::unique_lock<std::mutex>, bool> waitForTasks()
{
using namespace std::literals::chrono_literals;
std::unique_lock lock{m_mutex};
if (m_finishing || m_sleeping)
return {std::move(lock), true};
if (m_tasks.empty()) {
auto timedOutWithoutEntriesOrFinishing = !m_condition.wait_for(lock, 10min, [&] {
return m_tasks.size() || m_finishing || m_sleeping;
});
if (timedOutWithoutEntriesOrFinishing)
m_sleeping = true;
}
return {std::move(lock), m_finishing || m_sleeping};
}
[[nodiscard]] std::optional<Task> getTask(std::unique_lock<std::mutex> lock)
{
auto l = std::move(lock);
if (m_tasks.empty())
return {};
Task task = std::move(m_tasks.front());
m_tasks.pop_front();
return {std::move(task)};
}
template<typename Lock, typename TraceToken>
void ensureThreadIsRunning(Lock &lock, TraceToken traceToken)
{
using namespace NanotraceHR::Literals;
if (m_finishing || !m_sleeping)
return;
if (m_sleeping) {
lock.unlock();
joinThread();
lock.lock();
m_sleeping = false;
}
if (m_backgroundThread.joinable())
return;
auto [threadCreateToken, flowToken] = traceToken.beginDurationWithFlow(
"thread is created in the task queue"_t);
m_backgroundThread = std::thread{[this](auto traceToken) {
auto duration = traceToken.beginDuration(
"thread is ready"_t);
while (true) {
auto [lock, abort] = waitForTasks();
duration.end();
if (abort)
return;
auto getTaskToken = duration.beginDuration(
"get task from queue"_t);
if (auto task = getTask(std::move(lock)); task) {
getTaskToken.end();
m_dispatchCallback(*task);
}
}
},
std::move(flowToken)};
}
void clearTasks(Tasks &tasks)
{
for (Task &task : tasks)
m_clearCallback(task);
}
void stopThread()
{
{
std::unique_lock lock{m_mutex};
m_finishing = true;
}
m_condition.notify_all();
}
void joinThread()
{
if (m_backgroundThread.joinable())
m_backgroundThread.join();
}
private:
Tasks m_tasks;
std::mutex m_mutex;
std::condition_variable m_condition;
std::thread m_backgroundThread;
DispatchCallback m_dispatchCallback;
ClearCallback m_clearCallback;
bool m_finishing{false};
bool m_sleeping{true};
};
} // namespace QmlDesigner
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