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#pragma once
#include "base/assert.hpp"
#include "base/task_loop.hpp"
#include "base/thread.hpp"
#include "base/thread_checker.hpp"
#include <chrono>
#include <condition_variable>
#include <mutex>
#include <queue>
#include <utility>
namespace base
{
// This class represents a simple worker thread with a queue of tasks.
//
// *NOTE* This class IS thread-safe, but it must be destroyed on the
// same thread it was created.
class WorkerThread : public TaskLoop
{
public:
using Clock = std::chrono::steady_clock;
using Duration = Clock::duration;
using TimePoint = Clock::time_point;
enum class Exit
{
ExecPending,
SkipPending
};
WorkerThread();
~WorkerThread() override;
// Pushes task to the end of the thread's queue. Returns false when
// the thread is shut down.
bool Push(Task && t) override;
bool Push(Task const & t) override;
bool PushDelayed(Duration const & delay, Task && t);
bool PushDelayed(Duration const & delay, Task const & t);
// Sends a signal to the thread to shut down. Returns false when the
// thread was shut down previously.
bool Shutdown(Exit e);
TimePoint Now() const { return Clock::now(); }
private:
struct DelayedTask
{
template <typename T>
DelayedTask(TimePoint const & when, T && task) : m_when(when), m_task(std::forward<T>(task))
{
}
bool operator<(DelayedTask const & rhs) const { return m_when < rhs.m_when; }
bool operator>(DelayedTask const & rhs) const { return rhs < *this; }
TimePoint m_when = {};
Task m_task = {};
};
using ImmediateQueue = std::queue<Task>;
using DelayedQueue =
std::priority_queue<DelayedTask, std::vector<DelayedTask>, std::greater<DelayedTask>>;
enum class QueueType
{
Immediate,
Delayed
};
template <typename Fn>
bool TouchQueues(Fn && fn)
{
std::lock_guard<std::mutex> lk(m_mu);
if (m_shutdown)
return false;
fn();
m_cv.notify_one();
return true;
}
void ProcessTasks();
threads::SimpleThread m_thread;
std::mutex m_mu;
std::condition_variable m_cv;
bool m_shutdown = false;
Exit m_exit = Exit::SkipPending;
ImmediateQueue m_immediate;
DelayedQueue m_delayed;
QueueType m_lastQueue = QueueType::Immediate;
ThreadChecker m_checker;
};
} // namespace base
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